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INTRODUCTION — Running is one of the world's most popular forms of exercise, with millions of regular participants. In the United States alone, up to 40 million people run regularly, with more than 10 million running at least 100 days a year . Although running is an effective way to achieve many health benefits, it is associated with a high risk of injury; yearly, up to half of runners report an injury . Although some injuries are traumatic, most are due to overuse.
Given the popularity of running and the high rate of associated overuse injuries amenable to nonsurgical management, the primary care physician is likely to manage many injured runners and should be familiar with the diagnosis and treatment of the more common problems. The diagnosis and management of common lower extremity injuries associated with running are reviewed here. Detailed discussions of some specific injuries are found separately. (See "Ankle sprain" and "Patellofemoral pain" and "Hamstring muscle and tendon injuries" and "Stress fractures of the metatarsal shaft".)
GENERAL EPIDEMIOLOGY — The incidence of lower extremity injuries in runners ranges from 19.4 to 79.3 percent . The knee is the most commonly injured body part. The most common diagnoses include: patellofemoral pain, medial tibial stress syndrome (shin splints), Achilles tendinopathy, iliotibial band syndrome, plantar fasciitis, and stress fractures of the metatarsals and tibia [3-6]. According to a 2009 survey of more than 11,000 year-round runners, more than 10 percent experienced hip and/or low back pain in the previous 12 months . Among marathon runners, men report more hamstring and calf problems, whereas women report more hip complaints . Running is a common cause of injury among military personnel .
One retrospective survey of 2886 runners reported an overall injury rate of 46 percent, but found a higher incidence of soft tissue injuries to the calf, Achilles tendon, and hamstring among masters runners (>40 years), who comprised 34 percent of the participants . Injured runners were more likely to be male and to run six days per week and more than 30 miles each week.
RISK FACTORS — Despite the popularity of running and the prevalence of related injuries, few studies have successfully identified the individual factors most responsible, suggesting that many running injuries are multifactorial. A history of prior injury is one of the few variables that has consistently been shown to increase the risk of incurring a subsequent running injury [2,4,11]. Therefore, every injured runner seeking medical attention should be questioned about prior injuries, including treatments. Incomplete rehabilitation and failure to address potential risk factors associated with a prior injury increases the likelihood of recurrence. Greater mileage is another factor that is consistently associated with increased injury risk . Obesity is associated with an increased risk [13,14].
Multiple risk factors are likely to contribute to running injuries. These can be stratified into intrinsic risk factors (eg, anatomic and other individual variables, including gender and BMI) and extrinsic risk factors (eg, training variables and equipment).
Intrinsic risk factors
Anatomy — Running injuries have been attributed to a number of anatomic variables, but the literature does not support many of these commonly held beliefs. A prime example is patellofemoral pain, a common cause of knee pain in runners. Lower extremity alignment that results in a greater Q angle at the knee (common in women) has often been cited as a cause of patellofemoral pain, but the large majority of studies refute this assertion.
Foot type is another purported risk factor, but most studies of runners have not found consistent relationships between foot structure and specific injuries. One group studying collegiate cross country runners failed to identify any association between structural variations and the likelihood of developing exercise-related leg pain [15,16]. One notable exception is cavus foot (high arch), which is associated with myriad injuries [2,17]. Specific injuries implicated in one or more studies include tibial stress fractures, patellofemoral pain, plantar fasciitis, and Achilles tendinopathy. (See "Stress fractures of the tibia and fibula" and "Patellofemoral pain" and "Plantar fasciitis" and "Achilles tendinopathy and tendon rupture".)
Some researchers have proposed that limb asymmetry (ie, leg length discrepancy) may increase injury risk, including stress fracture, [18,19], but not all studies support this conclusion. These conflicting results suggest that anatomy alone is not sufficient to explain the high risk of injury among runners. Many experienced sports medicine clinicians believe that the important issue is whether the difference in leg length affects gait, rather than whether some measurement threshold is reached.
Gender and age — Gender and age may play a role in some running injuries, but the literature is conflicting in this regard:
●A prospective study of 844 male and female runners following a training program in preparation for a 10 km race reported an increased risk of injury among women age 50 or older and a lower risk among those 30 or younger .
●A prospective study of 532 novice runners participating in a 13-week training program noted that higher BMI was a risk factor for male but not female runners (hazard ratio [HR] 1.15; 95% CI, 1.05-1.26) . Conversely, navicular drop was associated with injury in females but not males (HR 0.85; 95% CI, 0.75-0.97).
●A longitudinal study of former high school cross country runners over a 15 year period reported that girls had significantly higher injury rates than boys (16.7 versus 10.9 injuries per 1000 athletic exposures) .
Studies consistently report an association between female gender and stress fracture risk, particularly among females with lower bone density, menstrual disturbances, and dietary deficiencies, as seen in the female athlete triad. The risk factors for stress fracture are discussed separately. (See "Overview of stress fractures", section on 'Risk factors'.)
While not consistently identified as a risk factor for running injury, age has been associated with a number of injuries in several observational studies. In contrast to the prospective study described above , a retrospective study of more than 2000 runners found that age under 34 was associated with an increased risk for patellofemoral pain in both men and women and an increased risk for iliotibial band syndrome, patellar tendinopathy, and tibial stress syndrome among men . These findings may reflect that master runners (>40 years) are primarily those with low injury rates, while runners who sustain multiple injuries are more likely to give up the sport.
Extrinsic risk factors — Studies have not consistently supported many traditional beliefs about the association between anatomic variations and injury risk . This has led many researchers to focus both on the effects of extrinsic factors on running injury and on the combination of intrinsic and extrinsic variables.
Training variables — Measures to reduce running injuries often include modifying training variables, such as mileage and intensity. A systematic review concluded that reducing the distance, frequency, and duration of running may be effective in preventing soft tissue injuries in runners .
In male runners, excessive mileage is associated with higher injury rates. Multiple observational studies report that training volumes of 65 kilometers (40 miles) or more per week increase the risk of injury [2,3,10,12]. While most sports medicine practitioners believe excessive mileage also affects female runners, well designed clinical studies have not been performed. It is unclear if more experienced runners are less susceptible.
Abrupt changes in training regimens can contribute to running injuries. Studies of military recruits report that sudden increases in training volume or changes in the type of training (eg, adding hill running) increase injury rates . Although many sports medicine physicians advocate the 10 percent rule (ie, increase training volume by no more than 10 percent per week), a randomized trial of this approach in 532 novice runners reported no reduction in injuries (20.8 versus 20.3 percent with standard training) . Nevertheless, common sense would suggest that gradual increases in training volume are less likely to cause injury than sudden increases.
Some types of training may be protective. As an example, one research group found that regular interval training is protective against knee injury . Running surface probably affects injury rates. Running on concrete is associated with increased risk, while running on a treadmill reduces the stresses placed on the tibia and may thereby reduce the risk of tibial stress fractures .
Stretching and warm-ups — It is hard to draw firm conclusions about the effectiveness of stretching for reducing the risk of running injuries due to the large number of variables involved. These variables include a runner's baseline flexibility, the timing of stretching (pre-exercise, post-exercise, or not in conjunction with exercise), and the method of stretching (eg, dynamic, static, or proprioceptive neuromuscular facilitation). Despite a dearth of convincing evidence, many sports medicine physicians, running coaches, and runners believe that stretching is beneficial. However, further research is needed to determine which runners benefit and what methods to use.
Multiple studies question the benefit of stretching, long a piece of injury prevention advice given to runners [29,30]. A systematic review of randomized trials that assessed multiple interventions designed to prevent running injuries included six studies involving 5130 runners that looked at stretching exercises and concluded that stretching regimens do not protect against soft tissue injury . The stretching regimens included in these studies varied in the muscle groups targeted, the timing of the intervention (eg, before or after training), whether a warm-up was also performed, and other factors. Another review that included both randomized trials and cohort studies investigating the effect of stretching on injury reduction during sports also concluded that stretching was not associated with a reduction in total injuries (OR 0.93; CI 0.78-1.11) .
Stretching may have other benefits. As an example, in a study of 900 military recruits, those who stretched regularly experienced lower rates of low back and soft tissue pain . Stretching may also play a useful role in the management of other injuries, such as plantar fasciitis and Achilles tendinopathy. (See "Plantar fasciitis" and "Achilles tendinopathy and tendon rupture".)
There is insufficient high-quality research in runners to determine whether warming up reduces injury rates. One randomized trial involving 421 runners found that an educational intervention regarding warm-up, cool-down, and stretching did not significantly reduce the risk of injury . Nevertheless, many clinicians advocate a dynamic warm-up or light jogging before engaging in strenuous running and we concur with this approach.
Shoes and orthotics — Debate continues about the role running shoes and orthotics may play in reducing the risk of injury. Based on limited evidence and clinical experience, we suggest using the running shoe that feels most comfortable and is well suited to the shape of the runner's foot [23,33,34].
There are three basic types of running shoes:
●Shoes for runners with a low foot arch (overpronators) that are designed to minimize foot motion and maintain the foot in a neutral position
●Shoes for runners with a neutral foot shape
●Shoes with extensive cushioning for runners with a cavus foot (oversupinators)
Many clinicians and runners believe that selecting the shoe best suited to the runner's foot type prevents injury; however, this concept is not well supported by the literature. Studies of recruits in the United States Marine Corps and Air Force undergoing basic training found that assigning shoes to recruits based on foot type did not significantly reduce injury rates [35,36]. In addition, a systematic review found insufficient evidence to support the prescription of running shoes based upon foot type , while the results of a subsequent trial suggest that the level of cushioning may not affect injury rates . In this trial, 247 recreational runners were randomly assigned to wear running shoes that differed only in midsole hardness for five months and to report their running volume and all running-related injuries. No significant difference was noted in injury rates between the two groups. One crossover randomized trial found that some popular, neutral-cushioned running shoes reduced plantar pressures in the cavus foot, theoretically reducing injury risk . It is possible that particular shoe types reduce the risk of injury in particular subpopulations of runners (eg, runners with cavus feet or pronated feet), but further study is needed to determine if this is so .
Regardless of shoe type, several studies of the shock absorption properties of running shoes have shown that new shoes lose up to half their cushioning after 250 to 500 running miles . Therefore, most sports medicine practitioners counsel runners to change their running shoes every 350 to 500 miles.
Orthotics may reduce the risk of some injuries. A randomized controlled trial of 400 military officer trainees found a significant reduction in lower extremity overuse injuries in the trainees given customized orthotics , while systematic reviews performed prior to this study concluded that orthotics "probably" reduce the risk of stress fracture [42,43]. Other reports have found that orthotics reduce the pain associated with patellofemoral pain and cavus foot, both common issues in runners [44-46].
Barefoot running and minimalist shoes — Although running barefoot or with "minimalist" shoes (eg, Vibram FiveFingers) is gaining popularity, few controlled studies of these approaches to running have been performed, and it remains unclear whether such shoes have negative or positive effects upon performance or injury rates . The potential benefits of barefoot running may be due to the changes in gait that are required when using this approach. These include a shorter stride length and a midfoot or forefoot strike, which is thought to reduce impact compared with the rearfoot strike used by many runners wearing traditional running shoes.
Given the limited evidence available, the indications and guidelines for transitioning to a barefoot style or minimalist shoes are anecdotal [48,49]. A review by a noted authority concludes that little is known about barefoot running, and there is much work to be done to determine whether a barefoot style can be used to treat or prevent injury . A few studies, mostly observational and involving small numbers of runners, suggest that some injuries (eg, stress fractures of the foot) occur more often in those using minimalist shoes, particularly if the transition to such footwear is not made gradually [51-55]. (See "Stress fractures of the metatarsal shaft" and "Stress fractures of the tarsal (foot) navicular".)
Gait, strength, and biomechanics — Many laboratory and observational studies have tried to determine the role of running biomechanics, vertical load, and plantar pressures in the development of running injuries. However, it is difficult to draw firm conclusions because many such studies involve small numbers and multiple factors are likely to contribute to the risk of injury. The following studies are illustrative:
●Multiple studies included in two systematic reviews have tried to assess ground reaction forces (GRF) and vertical load in runners with and without stress fractures and the results are mixed. Higher GRF and vertical load may be risk factors for stress fractures but such associations remain speculative [56,57].
●A study of 46 college students with running-related lower extremity injuries reported that specific components of gait, including increased pronation associated with increased pressure under the medial side of the foot, increased the risk of injury .
●A study of 45 healthy recreational runners found that subtle increases in step rate reduce the loads placed on the hip and knee during running, possibly reducing injury risk .
Nutrition and supplementation — Little data exists to confirm or refute associations between nutritional factors and running injuries, with the important exception of stress fractures in female runners. Multiple studies report that inadequate vitamin D, calcium, and calorie intake increases the risk of stress fracture in female military recruits and runners. In addition, a prospective study of 86 female runners found that low-fat intake increased the risk of sustaining a low extremity injury . (See "Overview of stress fractures", section on 'Risk factors'.)
While there is little high-quality evidence to support any particular diet to prevent running injuries, optimal nutrition does enhance performance and recovery; common sense suggests that runners should eat a balanced diet that includes adequate lean protein and all essential vitamins and minerals. A position paper on nutrition and performance authored jointly by Dietitians of Canada, the American College of Sports Medicine, and the American Dietetic Association makes the following recommendations for athletes :
●Consume adequate calories. Insufficient calories can lead to reduced muscle mass and bone density, cessation of menses, and delayed recovery, and can increase fatigue and the risk of injury and illness. In general, fewer than 1800 to 2000 kcals/day is inadequate for an exercising individual, although many female runners restrict calories to this level. Several tools are available to estimate calorie needs, including the Dietary Reference Intakes and the Dietary Guidelines from the United States Department of Agriculture (available at fnic.nal.usda.gov/interactiveDRI/).
●Consume adequate carbohydrates. Runners need approximately 6 to 10 gram/kg body weight of carbohydrates daily. Carbohydrates are critical for maintaining blood glucose during exercise and replenishing muscle glycogen. (See "Dietary carbohydrates".)
●Consume adequate protein. Endurance athletes need 1.2 to 1.7 g/kg body weight of protein daily.
●Consume adequate healthy fats. Healthy fats are a source of energy and provide essential fatty acids and fat-soluble vitamins, and should comprise 20 to 35 percent of total calorie intake. (See "Dietary fat".)
●Stay hydrated. Water loss of as little as 2 percent body mass can decrease performance . Runners should drink before, during, and after exercise. An easy rule of thumb is to weigh yourself before and after running, and drink 16 to 24 ounces (450 to 675 mL) of fluid for every pound (0.5 kg) lost during exercise. For long or intense exercise (eg, marathon), it is also important to replace electrolytes. (See "Exercise-associated hyponatremia".)
The timing of nutrient intake is important [61-63]. A snack high in carbohydrate, moderate in protein, and low in fat and fiber is generally well-tolerated prior to exercise, whereas a snack higher in fat and fiber may cause gastrointestinal cramping or other distress. During exercise that lasts more than one hour, the athlete needs fluids and small amounts of carbohydrate, such as that found in sports drinks. The runner should be encouraged to replenish glycogen stores by consuming carbohydrate, 1.0 to 1.5 g/kg of body weight, within 30 minutes of exercise, and to continue "refueling" every two hours for four to six hours. These goals can be met with relatively small amounts of food.
Some researchers suggest adding protein to post-training snacks to aid muscle recovery; this is likely most beneficial to the runner who does not take in adequate carbohydrate following exercise . Regardless of the specific approach, it is helpful for runners to become familiar with the concepts of "grams" and to learn how to apply this to their preferred foods.
Although an adequate, well-rounded diet provides the majority of vitamins and minerals needed by athletes, special mention should be made of iron. Iron requirements are greater in endurance runners than in non-endurance athletes . Iron is lost through sweat, the gastrointestinal tract, and menstruation. Thus, iron depletion is particularly common among premenopausal female runners. Any runner complaining of fatigue and decreased performance, especially females, should have a serum ferritin measured. If low, iron levels can be increased through diet and supplementation, but dietary replacement appears to be more effective .
Although muscle adapts to regular exercise, some exercise-induced muscle damage occurs, mediated in part by the production of reactive oxygen species (ROS). As antioxidants reduce ROS, some athletes take high doses of the antioxidants (eg, vitamins C and E) hoping to attenuate muscle damage. However, there is little evidence to support this practice, and there is some evidence that interfering with ROS signals may impair muscle performance . Runners should be informed of the potential risks associated with taking high doses of antioxidants [67,68].
Psychology — There is little evidence that psychological factors play an important role in running injuries. One study of 30 runners found that those with type A personality traits did not have higher injury rates than others, but did have a higher risk of multiple injuries . General studies of athletes have found a weak association between injury risk and such psychological factors as aggressiveness, exhaustion, and stressful life events .
Training suggestions to reduce injury risk — Despite the dearth of high-quality evidence to determine best practice , we have found the training tips listed below to be helpful and to reduce the risk of injury for many runners:
●Inexperienced runners often progress best using a combination of running and walking for a set time and gradually increasing the percentage of time spent running.
●Beginning runners should start with no more than 20 minutes of total training time per day and increase training time no more than 5 minutes every 14 days.
●Most beginners do best on an every other day training program, which enables gradual improvement of their aerobic and musculoskeletal fitness.
Mileage and rest guidelines:
●With the exception of elite runners, most individuals develop fewer injuries by limiting their total mileage to 40 miles (65 km) per week. (See 'Training variables' above.)
●Runs longer than 13 miles (20 km) are best done no more frequently than once every 14 days.
●Most individuals do best running no more than four or five days per week, with at least one rest day and one to two days doing other activities (ie, cross training).
●Runners should limit themselves to two to three marathons per year.
●Ease into training with a dynamic warm-up or light jog.
●Stretching before runs does not appear to reduce injuries; runners may do better stretching after their run or improving their strength and flexibility using other techniques, such as yoga or Pilates. (See 'Stretching and warm-ups' above.)
●Runners who experience frequent injuries are likely to benefit from running on a treadmill or a soft surface. Older athletes reduce their injury risk by running on soft surfaces. (See 'Training variables' above.)
●Runners need a solid base of aerobic fitness before adding speed work.
●Speed work is generally less risky if runners begin with the "Fartlek" (speed play) approach for 20 to 30 percent of their continuous runs for at least one month, before progressing to interval training (alternating fixed activity and rest periods) or timed repeat speed distances (eg, 10 sets of 200 m runs). Fartlek training consists of running at a faster pace at random times of variable duration during an otherwise standard distance run.
●Most runners need to limit the total mileage for interval or repeat distance speed training to 3 miles (5 km) or less.
●Fast downhill runs increase impact and injury risk and should be avoided.
●Athletes should select a running shoe that feels extremely comfortable and is well-suited to their foot structure (eg, high arch). (See 'Shoes and orthotics' above.)
●Barefoot running, while it may help to improve the biomechanics of some runners, probably only benefits those with sound running biomechanics at baseline and a foot structure that does not increase their injury risk, and should be limited to softer surfaces. Many running clinics are seeing an increase in metatarsal stress fractures in individuals new to this approach.
Nutrition and recovery:
●Runners should maintain adequate hydration and increase their salt intake if they tend to sweat heavily.
●Carbohydrate and protein intake soon (within about 30 minutes) after an intense workout speeds recovery. (See 'Nutrition and supplementation' above.)
Supplemental strength training:
●Many runners have disproportionately strong hamstrings. Cross training with a road or stationary bicycle or other equipment that develops quadriceps strength helps to balance the hamstring dominance of runners.
●Many runners have weak hip flexors and hip abductors. Performing supplemental strength exercises for these muscles may reduce the risk of injury.
●Achilles tendon flexibility wanes with age. Regular performance of eccentric strength exercises for the calf complex may help prevent injury. (See "Achilles tendinopathy and tendon rupture", section on 'Rehabilitation using resistance exercise'.)
EVALUATION OF THE INJURED RUNNER — Evaluation of the injured runner begins with a thorough history, which should include inquiries about:
●Prior injuries and related treatments (including the runner's compliance with treatment)
●Current training patterns, including mileage, frequency, and training methods (eg, hill running); Inquire about changes in training that preceded the injury
●Shoe and orthotic use, including any recent change in shoes
●Training surface, including any recent change
●Injury details (eg, what provokes and reduces symptoms, duration of symptoms)
●Athletic activities other than running
●Detailed training history, including running and racing experience
●Medical conditions; prior surgeries
●Medication and supplement use
Examination of the injured runner includes assessment not only of the injured area but of all related structures (ie, the runner's entire "kinetic chain"), noting any imbalances or deficits in structure (eg, leg length discrepancy), strength, flexibility, or motion. Discrepancies may exist between legs or between muscle groups of the same leg (eg, quadriceps disproportionately stronger than hamstrings). One way to organize each element (eg, observation, strength testing) of the physical examination is to begin with proximal structures (eg, spine and pelvis) and work distally. Careful observation of the patient's walking and running gaits helps to confirm that the anatomic problems identified during a stationary examination affect biomechanical performance.
Begin your assessment by asking the injured runner to stand in front of you, noting their posture and lower extremity alignment. Observe the legs from hip-to-foot looking for symmetry. Note the structure of the knee, especially genu varum (which may be associated with iliotibial band syndrome or medial meniscal pathology) or valgus (often seen in women with patellofemoral pain). Note the position of the patella and any apparent muscular asymmetry. Ask the patient to stand on one foot and then the other, watching for balance, control, and posture. Does the unsupported hip sag (ie, a positive Trendelenburg test)? A positive Trendelenburg test suggests weakness of the gluteus medius, a common finding in runners with hip and knee pain. Make note of foot structure and position. Does the runner have a normal, high, or flat arch? Ask the patient to walk and to squat. Watch for a limp, stiffness of one limb, and a tendency to shift weight off one limb.
Screen for tenderness and altered mobility of the spine, pelvis (including sacroiliac joints), hips, knees, ankles, and feet before turning your attention to the area of complaint. Be sure to assess muscle strength and neurovascular status throughout the lower extremity. Weakness of the hip musculature (particularly hip abductors) is common among novice runners, frequently contributing to lower extremity pain, especially patellofemoral pain. (See "Patellofemoral pain".)
The following findings may be noted during the examination:
●Hip flexion, rotation, or abduction weakness is present with many lower extremity injuries, particularly those affecting the hip or knee.
●Increased lumbar lordosis suggests weak anterior core muscles, a common condition in runners with hip weakness.
●Vastus medialis atrophy or asymmetry can occur with patellofemoral pain, or in athletes who have had knee surgery.
●Tenderness along the medial tibial border bilaterally is often present with medial tibial stress syndrome (MTSS), or "shin splints."
●Loss of normal lumbar lordosis (with or without back pain) is often present with tight hamstrings.
●Loss of internal rotation of the hip occurs with femoral neck stress fracture.
●Asymmetry of the quadriceps muscles is common in runners with osteoarthritis of the hip.
●Pain and/or a sense of "catching" in the groin with the knee flexed to 90 degrees suggests a labral tear, but also may be seen with iliopsoas tendinopathy.
●Localized tenderness and a positive hop test suggest a tibial stress fracture.
●Achilles tendon thickening or nodules suggests Achilles tendinopathy.
●Tenderness at the medial insertion of the plantar fascia into the calcaneus suggests plantar fasciitis.
●Hallux limitus or hallux rigidus and reduced ankle dorsiflexion can develop with plantar fasciitis or calf muscle injuries.
●Splayed toe sign and forefoot widening can occur with metatarsalgia.
●Leg length inequality may be present with stress fractures, and possibly with iliotibial band syndrome and lower back and pelvic injuries.
Diagnostic imaging, including plain radiographs, ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), and bone scan may be necessary in some cases to make a definitive diagnosis. However, the clinician should have a clear differential diagnosis in mind before ordering such studies.
Once a diagnosis is made and a treatment plan established, the clinician and athlete should work together to uncover and eliminate potential contributing factors, as many running injuries appear to be multifactorial. The mainstay of treatment for the vast majority of running injuries is "relative rest," which means stopping running, or at a minimum significantly reducing mileage, while the injury heals. Depending upon the injury, most runners can maintain reasonable conditioning by performing non-impact exercises in a pool or on a bike, or by using other equipment (eg, rowing machine).
Overview and approach — Hip injuries are less common in runners than injuries to the lower extremity and they can be difficult to diagnose. Nevertheless, during jogging, the hip joint is subjected to loads up to eight times body weight and both acute and chronic injuries can occur . In runners, the differential diagnosis of hip pain includes gluteus medius tendinopathy, piriformis syndrome, stress fracture of the femoral neck, labral tear, and, less often, radicular pain from the lumbar spine. Better understanding of the functional anatomy of the hip suggests a correlation between hip muscle weakness and injury to the low back or lower extremity in athletes, including runners [72-74].
Gluteus medius weakness and tendinopathy and piriformis syndrome — The gluteus medius originates along the external surface of the ilium and runs distally and laterally to its attachment on the greater trochanter of the femur (figure 1). The gluteus medius abducts the hip and assists with pelvic stability during running. Weakness of the muscle typically causes pain with hip abduction and rotation. Pain generally increases when the muscle is stretched and there may be focal tenderness at the muscle's insertion, just medial and superior to the greater trochanter. Difficulty maintaining a level pelvis while standing on one leg (positive Trendelenburg sign) may be noted.
The piriformis muscle is a small but important external rotator of the hip that crosses the sciatic nerve and is believed by some to cause sciatica-type pain when it compresses the nerve [75,76]. However, the existence of this so-called "piriformis syndrome" remains controversial and diagnosis is difficult [77-79]. Piriformis syndrome in the runner may be associated with foot overpronation, weakness of the gluteal muscles and other hip abductors, and tightness of the hip adductors.
The mainstay of treatment for both gluteus medius tendinopathy and piriformis syndrome is physical therapy and correction of biomechanical abnormalities. Orthotics and massage therapy may be useful; acetaminophen and nonsteroidal antiinflammatory drugs may be used for analgesia. There are reports of using injections of local anesthetics, glucocorticoids, and botulinum toxin (Botox) to treat piriformis syndrome .
Femoral neck stress fracture — Stress fractures of the femoral neck are an uncommon but important cause of hip or groin pain in the adult runner because of the relatively high risk of nonunion. (See 'Stress fractures' below and "Femoral stress fractures in adults".)
Labral tear — The acetabular labrum is a ring of fibrocartilage and dense connective tissue attached to the bony rim of the acetabulum. It is thought to be largely avascular. Although the labrum's function is not fully understood, it is thought to provide stability and decrease the stress placed on the hip joint. Therefore, a significant tear in the labrum can increase stress on the hip joint, decrease stability, and ultimately lead to damage of the articular cartilage.
Labral tears are reported in sports that require frequent hip rotation, such as soccer and hockey, and in runners, especially female runners. Runners with a labral tear typically complain of pain in the anterior hip or groin. They may have mechanical symptoms, including clicking, locking, catching, or giving way (so-called "snapping hip"). Other hip injuries that may produce such mechanical symptoms include iliopsoas tendinopathy.
Labral tears are complex and often frustrating to treat. Physical therapy has mixed results. Arthroscopic surgery is often helpful, but the recovery can be prolonged. Runners diagnosed with labral tears should be counseled carefully regarding the paucity of evidence for determining the best treatment and the benefits and risks of each approach.
Iliopsoas tendinopathy — Iliopsoas tendinopathy produces symptoms similar to a labral tear but presents more often as anterior hip pain in younger athletes, especially after a rapid growth spurt, and is more easily treated. Athletes who repeatedly engage in forceful flexion of the hip, including track and field athletes (eg, hurdlers, jumpers), are at greatest risk. Examination usually reveals tight, painful hip flexors (figure 2). Iliopsoas tendinopathy typically responds within a few weeks to activity modification, acetaminophen and nonsteroidal antiinflammatory drugs, and physical therapy.
Knee and thigh injuries
Knee pain (patellofemoral pain) — Knee pain is among the most common complaints from runners. Most such runners are diagnosed with patellofemoral pain (PFP). Despite the prevalence of this diagnosis, no consensus exists about its etiology or the factors most responsible for causing pain. Overuse and malalignment are commonly cited causative factors. In addition, runners (especially females) with PFP often have decreased strength in hip abduction, external rotation, and extension compared to healthy controls. Patients with PFP typically complain of anterior knee pain that worsens with squatting, running, prolonged sitting, or when ascending or descending steps. Pain is often poorly localized "under" or "around" the patella. Details about the diagnosis and management of PFP are provided separately. (See "Patellofemoral pain".)
Iliotibial band syndrome — The iliotibial band (ITB) consists of connective tissue that runs from the ilium to the anterolateral aspect of the proximal tibia (figure 3). It is involved in hip abduction and internal rotation, knee extension and flexion, and helps to stabilize the knee during running.
The iliotibial band syndrome (ITBS), which occurs primarily in runners, is characterized by an aching or burning pain at the site where the ITB courses over the lateral femoral condyle; occasionally the pain radiates up the thigh toward the hip. Runners often complain of such lateral knee pain while running, but pain may persist after training, especially with activity that requires repetitive flexion and extension of the knee, such as ascending or descending stairs or standing from a seated position. The diagnosis of ITBS is clinical; no imaging is typically needed. A detailed discussion is provided separately. (See "Iliotibial band syndrome".)
Hamstring injuries — Hamstring injuries are typically acute; the injured runner complains of developing a sudden, sharp pain in the posterior thigh while running at high speed or up hills (figure 1). Examination findings depend upon the severity of injury and may include a limping gait (due to the inability to fully extend the knee); ecchymosis; a visible or palpable defect in the hamstring muscle; focal tenderness; and pain or weakness with muscle contraction. Details about the diagnosis and management of hamstring muscle injuries are provided separately. (See "Hamstring muscle and tendon injuries".)
Knee and hip osteoarthritis — Exercise is recommended for most patients with osteoarthritis (OA) of the hip or knee. Although water-based exercise is often suggested, multiple studies confirm the value of regimens involving full weightbearing exercise. (See "Nonpharmacologic therapy of osteoarthritis", section on 'Exercise and physical therapy'.)
Despite this evidence, many clinicians subscribe to the traditional teaching that patients with osteoarthritis (OA) of the knee or hip should not run because it exacerbates the condition. The medical literature, however, does not support the contention that running contributes to the degeneration of articular cartilage [81,82]. Examples of such studies include:
●A large follow-up study using questionnaires completed by established cohorts of runners and walkers reported reduced risk among runners for developing OA or requiring hip replacement surgery compared with those participating in other exercise . Risk dropped substantially in those who ran ≥12.9 km/week (8 miles/week). The authors attribute much of the effect to the lower body mass index among runners.
●A prospective cohort study followed 45 runners and 53 controls over 18 years and, using a validated score to assess for OA, found no difference between the two groups in the progression or the number of severe cases of knee OA .
●Another prospective study of 16 runners and 13 non-runners found no evidence that running predisposes to OA of the lower extremities .
●Multiple retrospective studies have found no evidence of premature damage of articular cartilage or increased risk for OA among long-distance runners [85-87].
●Small clinical and laboratory studies using MRI to evaluate the knees of long-distance runners report no significant damage to articular cartilage following a race and no major differences when images were compared to those of active non-runners [88-90].
Stress fractures — Stress fractures in runners occur most often in the tibia, but can develop in any bone of the lower extremity, including the metatarsals, navicular, and femoral neck . Detailed discussions of stress fractures, including a description of those at high risk for nonunion, appear separately; a brief description and information of particular importance for runners is provided here. (See "Overview of stress fractures" and "Stress fractures of the tibia and fibula" and "Stress fractures of the metatarsal shaft" and "Femoral stress fractures in adults" and "Stress fractures of the tarsal (foot) navicular".)
When evaluating the runner with a suspected stress fracture, the clinician should ask for a description of the pain, running patterns and recent changes in training, shoe and orthotic wear, and prior injuries. Information about the patient's nutrition and menstrual history, and any family history of metabolic bone disease, are also important.
Typically, the runner with a stress fracture complains of focal pain that is insidious in onset, increases as a run progresses, and improves with rest. Over time, if the athlete persists in running despite such symptoms, pain occurs with less strenuous activity and ultimately at rest. Some runners present with acute onset of severe pain, which may result from a complete fracture at the site of a preexisting stress fracture.
Important risk factors for developing stress fractures include a history of prior stress fracture, increasing volume and intensity of training, poor running biomechanics, female gender and menstrual irregularity, a diet poor in calcium, and poor bone health . The management of stress fractures in runners is discussed separately. (See "Overview of stress fractures", section on 'Treatment concepts'.)
The clinician should be aware that stress fractures at high risk for nonunion (eg, femoral neck and navicular) are more common in runners than in other athletes. If a high-risk stress fracture is suspected, an aggressive work-up is warranted and immediate orthopedic consultation should be obtained if the diagnosis is confirmed. A history of recurrent stress fracture or a fracture in cancellous bone suggests that the runner's bone mineral density may be low and should be measured.
Femoral neck stress fractures should be suspected in any distance runner with groin pain of insidious onset, especially female distance runners at risk for the "female athlete triad" (eating disorder, amenorrhea, and osteoporosis). The female athlete triad is reviewed separately. (See "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations".)
Navicular stress fractures occur more often in male athletes participating in track and field events (eg, hurdlers, jumpers, sprinters) and middle distance runners . The athlete with a navicular stress fracture often presents with insidious pain in the midfoot or arch that increases with jumping.
Medial tibial stress syndrome (shin splints) and tibial stress fractures — Clinicians confronted by runners with shin pain must distinguish between stress fractures of the tibia and medial tibial stress syndrome (MTSS), often referred to as "shin splints." Although the history may be similar, a focal, palpable area of tenderness is present in most patients with stress fractures, whereas tenderness is much more diffuse and there are no discrete palpable lesions in those with MTSS. Imaging may be necessary in some cases to rule out a stress fracture. Plain radiographs are normal in patients with shin splints, but may also be unrevealing early in the course of a stress fracture. (See "Stress fractures of the tibia and fibula", section on 'Clinical presentation and examination' and "Stress fractures of the tibia and fibula", section on 'Diagnostic imaging'.)
Distinguishing between the two diagnoses affects treatment: a runner with a stress fracture should avoid running and pursue non-impact activities like swimming or cycling while the stress fracture heals, while the runner with MTSS can continue running but should reduce the total mileage. A systematic review found that shock-absorbing insoles may reduce symptoms and prevent recurrence of MTSS . Risk factors may include obesity and limited mobility of the ankle and hip .
Chronic exertional compartment syndrome — Chronic exertional compartment syndrome (CECS) occurs when increased pressure within a muscle compartment reduces blood flow, leading to muscle ischemia and pain when metabolic demands cannot be met. The patient with CECS is often a young runner who describes gradually increasing pain in a specific muscle region (usually the lower leg) during exertion. The pain may be described as aching, squeezing, cramping, or tightness. Pain generally begins within several minutes of starting a run, often at a specific point in training. Runners can often describe the time or distance required for symptoms to develop. Pain resolves completely with rest, although not immediately upon stopping exercise. The diagnosis and management of CECS is discussed in detail separately. (See "Chronic exertional compartment syndrome".)
Foot and ankle injuries — Foot and ankle injuries account for up to 20 percent of running injuries, and are the most common injury reported by distance runners and marathoners . This is not surprising given that the ground reaction forces the foot must absorb with each stride are several times body weight. The most common foot injuries in runners are overuse injuries of soft tissues, including tendons and fascia.
Plantar fasciitis — Plantar fasciitis (PF) is the most common cause of rearfoot pain in runners. The predominant symptom of PF is pain in the plantar region of the foot that increases when initiating push-off while walking or running. The hallmark for diagnosis is focal point tenderness. The etiology of PF remains unclear but the condition is often attributed to training errors, biomechanical problems, and excessive foot pronation or supination, and is more common in older and heavier runners [94-96]. The biomechanical abnormality most often associated with PF is decreased dorsiflexion of the foot and toes and thus stretching is an important part of treatment. Another common biomechanical problem is weakness of the plantar flexors, which some clinicians believe is best treated with eccentric strengthening exercises. The diagnosis and management of PF is reviewed separately. (See "Plantar fasciitis".)
Tendon injuries — Runners are susceptible to tendon injuries at a number of sites, the Achilles being most common. Others include the peroneal, posterior tibial, and anterior tibial tendons (figure 4).
Achilles tendinopathy occurs in up to 10 percent of elite runners annually ; runners with more than 10 years of experience are at higher risk . Among former elite male distance runners, the lifetime risk is reported to be as high as 52 percent . The biomechanical factors that predispose runners to Achilles tendinopathy remain unclear but are the subject of research [100-102]. Poor flexibility of the Achilles tendon, overpronation, and valgus or varus deformity of the calcaneus all affect rear-foot mechanics, possibly increasing torque on the Achilles. Some clinicians advocate using a heel pad or orthotic in runners to counteract this effect.
Patients with Achilles tendinopathy typically complain of pain or stiffness 2 to 6 cm above the posterior calcaneus. The pain is frequently described as burning, increases with activity, and is relieved by rest. Runners with the condition often have recently increased their training intensity or have been training rigorously for a long time. A history of excessive foot supination, increased speed work or hill training, or improper (eg, poorly fitting shoes, tennis instead of running shoes) or worn out footwear may be found. The diagnosis and management of Achilles tendinopathy is discussed separately. (See "Achilles tendinopathy and tendon rupture".)
Peroneal tendon injury may be traumatic, usually from a lateral ankle sprain, or related to overuse and associated with excessive foot pronation and weak foot plantar flexors. Examination reveals tenderness along the course of the tendon posterior or inferior to the lateral malleolus, which increases with resisted eversion. The diagnosis and management of non-Achilles tendinopathies are discussed separately. (See "Non-Achilles ankle tendinopathy".)
Posterior tibial tendinopathy is typically an overuse injury that develops following an abrupt increase in training intensity, and is associated with poor foot and calf flexibility and excessive foot pronation. Examination findings include tenderness along the course of the posterior tibial tendon posterior or inferior to the medial malleolus, which increases with resisted inversion.
Anterior tibial tendinopathy is a common cause of anterior ankle pain in runners, and often develops following abrupt increases in training, particularly hill running. Examination often reveals tenderness, and possibly swelling, of the tendon as it crosses the ankle joint. Pain increases with resisted dorsiflexion.
Overuse tendinopathy generally is reviewed in detail separately. (See "Overview of the management of overuse (chronic) tendinopathy" and "Overview of overuse (chronic) tendinopathy".)
Navicular stress fracture — Stress fractures of the tarsal navicular are more common in runners. These injuries present in a manner similar to other stress fractures and are associated with vague medial midfoot pain and focal tenderness, most often along the dorsal aspect of the navicular. (See 'Stress fractures' above and "Stress fractures of the tarsal (foot) navicular".)
First metatarsal phalangeal joint — Running generates substantial forces across the forefoot and thus can aggravate hallux rigidus or hallux valgus (bunion) of the metatarsal phalangeal (MTP) joint of the great toe (ie, first MTP joint). The sesamoid bones located on the plantar surface of the MTP joint can become inflamed from running and may cause discomfort.
Hallux rigidus and hallux valgus (bunion) — There is little high-quality evidence to provide insight into the causes and guide the management of hallux rigidus. Hallux rigidus is presumed to be a degenerative condition of the first MTP joint associated with either an acute injury (eg, forced hyperextension of the great toe, so-called "turf toe") or repetitive microtrauma, as would occur with running [103,104]. Genetic predisposition may play a role. The result is limited dorsiflexion of the first MTP joint; approximately 60 degrees of dorsiflexion is needed for normal gait.
Runners with hallux rigidus are typically older than 30 and complain of pain at the dorsum of the great toe. However, some runners may present with vague lateral forefoot pain. This presentation is likely due to runners shifting their body weight to the lateral foot during the foot-strike phase of running to reduce the load on the great toe. It remains unclear whether running is a cause of hallux rigidus or aggravates symptoms elicited by other factors. Shoes with a toe box that is too small or pointed may contribute.
Hallux valgus (ie, bunion) deformity is defined as a lateral deviation of the hallux (great toe) on the first metatarsal. The etiology of hallux valgus is multifactorial and likely involves abnormal mechanics and anatomy. Patients generally complain of a deformed and painful great toe. (See "Hallux valgus deformity (bunion)".)
In runners with either of these conditions, mechanically limiting first MTP joint motion by using appropriate shoes and unloading techniques can be helpful. We suggest walking shoes with a wide toe box, stiff soles, rocker bottoms, and low heels. Comfortable running shoes with a wide toe box combined with techniques to reduce the impact on the first MTP joint, such as custom orthotics or cushioned insoles, reduce symptoms in many runners. Acetaminophen or nonsteroidal antiinflammatory drugs may be used for short-term pain relief. Ice can be applied following running. Glucocorticoid injections may provide short-term pain relief for those with mild hallux rigidus . Consultation with a foot surgeon should be obtained for severe or recalcitrant cases, although there is little high-quality evidence to guide decisions about surgery or conservative care.
Sesamoiditis — The sesamoids are pea-sized bones that function as pulleys for tendons (just as the patella does for the knee extensors) and assist with weightbearing. Inflammation or injury of the sesamoid bones located on the plantar surface of the first MTP joint can cause focal pain in runners, particularly sprinters (image 1 and figure 5). The runner with sesamoiditis typically complains of pain at the area of the MTP joint with weightbearing that is exacerbated by walking, and even more so by running. Exquisite tenderness of the sesamoids is present, and is exacerbated by dorsiflexion of the great toe. Imaging is required to differentiate between sesamoiditis and a stress fracture.
Both sesamoiditis and sesamoid stress fractures are notoriously difficult to treat and may require a short period of immobilization followed by prolonged rest from running. Runners can use alternative, nonweightbearing forms of exercise to maintain fitness. Treatment with custom orthotics, soft pads cut to relieve pressure on the sesamoids, and in severe cases glucocorticoid injections may be helpful, but there is little evidence to guide treatment. Women runners should avoid wearing high heels; shoes with a stiff sole (eg, clog) are often helpful. Consultation with a foot surgeon is reasonable in recalcitrant cases.
Treatment of sesamoiditis does not differ significantly from that for sesamoid fractures. The evaluation and management of sesamoid fractures is discussed separately. (See "Sesamoid fractures of the foot".)
Metatarsal stress fracture and metatarsalgia — Pain in a runner's forefoot that is not due to a metatarsal stress fracture is likely due to metatarsalgia or an interdigital neuroma. (See 'Stress fractures' above.)
Metatarsal stress fractures typically present in a manner similar to other stress fractures and are associated with vague forefoot pain of insidious onset and focal tenderness over a particular metatarsal. (See "Stress fractures of the metatarsal shaft".)
Metatarsalgia is a general term for pain that occurs along the ball of the foot. Most runners with metatarsalgia complain of pain in the forefoot during running; the examiner will find tenderness along the plantar surface just proximal to the metatarsal heads. The condition is often associated with overpronation and/or collapse of the transverse arch. A metatarsal pad placed proximal to the area of tenderness often relieves symptoms; in more severe cases, a custom orthotic may be needed.
Morton neuroma — Interdigital neuromas (often referred to as Morton neuroma) are thought to be due to swelling and scar tissue formation on the small interdigital nerves. They most commonly involve the third interdigital space, but may also develop in the second and fourth. An intermetatarsal bursitis can cause a similar pain.
The runner with a neuroma may complain of numbness of the involved toes or pain that increases with activity and is usually felt between the third and fourth toes (figure 6). Examination may reveal a clicking sensation (Mulders sign) when palpating this interspace while simultaneously squeezing the metatarsal joints. Overpronation and tight shoes are often associated with the condition.
Ultrasound offers an inexpensive option for identifying Morton neuroma with accuracy comparable to magnetic resonance imaging (MRI), and can help to distinguish a neuroma from intrametatarsal bursal swelling or synovitis in adjacent joints.
Conservative treatment should precede expensive diagnostic procedures. This approach involves decreasing pressure on the metatarsal heads by using a metatarsal support or bar or padded shoe insert. Strength exercises for the intrinsic foot muscles are often part of conservative treatment. Treatment inserts are often placed in both shoes, even when symptoms are unilateral, to ensure that the patient walks evenly, but bilateral pads are not always needed. A broad-toed shoe that allows spreading of the metatarsal heads may be helpful. Morton neuroma is discussed in greater detail separately. (See "Evaluation and diagnosis of common causes of foot pain in adults", section on 'Morton neuroma'.)
Tarsal tunnel syndrome — Tarsal tunnel syndrome (TTS) is an uncommon source of foot pain in runners due to entrapment of the posterior tibial nerve (PTN) or one of its branches as it courses behind the medial malleolus. The most common causes include an acute injury and its sequelae (eg, scar tissue) or repetitive microtrauma, as occurs with running, particularly in runners who overpronate. Runners with TTS complain of numbness or burning pain, usually along the plantar surface of the foot, although complaints may be localized to the medial plantar surface of the heel, mimicking plantar fasciitis. TTS typically worsens with running or at night. Findings are almost always sensory; muscle weakness is uncommon. A positive Tinel sign may be present. As in carpal tunnel syndrome, a positive sign occurs when symptoms are elicited by tapping over the path of the nerve. TTS is discussed in detail separately. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Tarsal tunnel syndrome'.)
Toenail injuries — Athletes in many sports sustain toenail injuries from repetitive trauma to the nail or nail bed. In runners, this condition is commonly called "jogger's toenail", and it most frequently affects the great toe (picture 1) . The nail may turn black (due to subungual bleeding) or may fall off, especially after a long distance run such as a marathon. The differential diagnosis for these injuries includes fungal infection and subungual melanoma. The management of acute subungual hematoma, fungal infection of the nail (onychomycosis), and melanoma are reviewed separately. (See "Subungual hematoma" and "Onychomycosis: Epidemiology, clinical features, and diagnosis" and "Initial surgical management of melanoma of the skin and unusual sites", section on 'Subungual'.)
In the author's experience, toenail injuries in runners are most often due to poorly fitting shoes. Thus, injuries can be prevented by using properly fitted running shoes. Such shoes provide sufficient space in the toe-box and are sized to accommodate the longest toe. The midfoot portion of the shoe should fit properly and be sufficiently snug to prevent the toes from slipping forward and striking against the end of the toe box.
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Achilles tendinopathy (The Basics)" and "Patient education: Metatarsalgia (The Basics)" and "Patient education: Patellofemoral pain (The Basics)" and "Patient education: Iliotibial band syndrome (The Basics)" and "Patient education: Hamstring injury (The Basics)" and "Patient education: Shin splints (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Up to half of regular runners report an injury each year. Some injuries are traumatic, but most are due to overuse and many of these involve the knee. The most common diagnoses include: patellofemoral pain, medial tibial stress syndrome (ie, "shin splints"), Achilles tendinopathy, iliotibial band syndrome, plantar fasciitis, and stress fractures of the metatarsals and tibia. (See 'General epidemiology' above.)
●A number of intrinsic and extrinsic risk factors are associated with running-related lower extremity injuries. Perhaps the most important and most easily changed are training variables, such as mileage and intensity. The role of other factors, such as shoes, stretching, and biomechanics, is less clear. Training suggestions to reduce the risk of injury are provided in the text. (See 'Risk factors' above and 'Training suggestions to reduce injury risk' above.)
●A careful history and physical examination are essential for determining the differential diagnosis and the need for diagnostic imaging. Guidance about how best to evaluate the injured runner is provided in the text. (See 'Evaluation of the injured runner' above.)
●Descriptions of important and common causes of running-related lower extremity injuries, organized anatomically, are provided in the text, along with links to more detailed discussions. (See 'Specific injuries' above.)
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