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Patient information: Knee pain (Beyond the Basics)


The knee is a "hinge" type joint that allows the leg to bend and straighten (flex and extend) (picture 1). Of all the joints in the body, the knee is at the greatest risk of injury, age-related wear and tear, inflammatory arthritis, and septic (infection-related) arthritis.


There are many conditions that can cause knee pain.

Patellofemoral pain syndrome — This is a group of symptoms most commonly caused by overuse of the knee. It affects many running athletes, and is more common in women than men. It causes pain in the front of the knee, and pain may worsen with squatting, running, prolonged sitting, or when climbing or descending steps. (See "Patellofemoral pain syndrome".)

Bursitis — The knee is lubricated by joint fluid that is produced by the lining of the joint and by six lubricating "bursa" sacs. The bursa sacs can become irritated as a result of injury, excessive pressure, or overuse; inflammation of a bursa is called bursitis. (See "Patient information: Bursitis (Beyond the Basics)".)

Joint effusion — After a knee injury, excessive fluid can accumulate inside the joint. This is called "water on the knee" or a joint effusion.

Arthritis — The cartilage covering the ends of the bones and the undersurface of the knee cap (surface or articular cartilage) can become worn down, irritated, or irregular, a condition known as arthritis. (See "Patient information: Osteoarthritis symptoms and diagnosis (Beyond the Basics)".)

Meniscal tears — Specialized "shock absorber" cartilage located between the thigh and leg bones (meniscal cartilage) can be damaged, a condition known as a torn meniscus.

Cruciate ligament sprain or tear — The knee joint is held tightly together by four ligaments: the inner and outer fan-shaped hinge ligaments (medial and lateral collateral ligaments) and the crossing (cruciate) ligaments, which sit in the middle of the joint (the anterior and posterior cruciate ligaments) (picture 2).

The collateral ligaments are firmly attached to the far end of the femur (thigh bone) and the near end of the tibia and fibula (lower leg bones). They function to hold the two bones together and prevent side-to-side motion. The cruciate ligaments are firmly attached to the far end of the femur and near end of the tibia. (See "Patient information: Anterior cruciate ligament injury (Beyond the Basics)".)

Muscle strain — The quadriceps muscle (in the front of the thigh) and the hamstring muscles (in the back of the thigh) support and move the knee joint. Loss of strength in these muscles from injury or disuse causes the knee joint to become unstable.

Significant weakening of muscle can cause the knee to "give out," potentially leading to a fall and further injury. Excessive use or a rapid contraction (ie, from sprinting or jumping) can strain the quadriceps or hamstring muscles.

Knee injuries — Pain in the knee can also occur after an injury:

Acute injuries may be caused by breaks in the bones, torn cartilage, ligament rupture, or increased joint fluid due to a severe knee strain, infection, arthritis, or bleeding. Most acute injuries cause severe pain and swelling.

More subtle injuries, such as partially torn cartilage or tendon, and ligament sprains cause less swelling, pain, and minimal difficulty walking or bending the knee

Overuse or excessive use of the knee can cause patellofemoral pain syndrome, arthritis flares, bursitis, or a knee strain and effusion.

Wear and tear over time; painful knee caps and arthritis are the two most common causes of knee pain in people without knee injuries.


Physical therapy is essential to the treatment, rehabilitation, and prevention of many of the conditions that affect the knee joint and its surrounding supporting structures. Physical therapy for knee pain often includes ice, elevation, and muscle-toning exercises.

Activity limitations — To speed recovery and protect against future knee damage, activities that cause pain should be avoided temporarily.

The following positions and activities place excessive pressure on the knee joint and should be limited until knee pain and swelling resolve:



Twisting and pivoting

Repetitive bending (multiple flights of stairs, getting out of a seated position, clutch and pedal pushing, etc.)


Aerobics, dancing

Playing stop and go sports (basketball, sports that use racquets)

Swimming using the frog or whip kick

The following types of exercise equipment also place excessive pressure on the knee joint and should be limited until knee pain and swelling resolve:

Stair stepper

Stationary bicycle

Rowing machine

Universal gym utilizing leg extensions

The preferred exercise equipment for the knee should provide smooth motion of the knee, maximal toning of the front and back thigh muscles (quadriceps and hamstring muscles), minimal jarring and impact to the joint, and the least amount of bending to accomplish toning. These activities are acceptable alternatives to the above:

Fast walking

Water aerobics

Swimming using the crawl stroke

Cross country ski machines

Soft platform treadmill

Ice and elevation — Ice is useful for the control of pain and swelling. It can be applied to the knee for 15 to 20 minutes as often as every 2 to 4 hours, particularly after physical activity. A bag of ice, frozen vegetables, or a frozen towel work well. The swollen knee should be elevated above the level of the heart while icing.

Pain relief — If needed, a non-prescription pain medication such as acetaminophen (Tylenol®), ibuprofen (eg, Advil®, Motrin®) or naproxen (eg, Aleve®) can be taken. (See "Patient information: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)".) No more than 4000 mg of acetaminophen is recommended per day. Anyone with liver disease or who drinks alcohol regularly should speak with his or her healthcare provider before taking acetaminophen.

Strengthening exercises — Rehabilitation of the knee begins with gentle strengthening exercises. These exercises are performed without bending the affected knee.

Straight leg raises — Sit on the edge of a chair or lie down on the back. Bend the opposite leg (picture 3). Keep the affected leg perfectly straight and raise it 3 to 4 inches off the ground. Hold for 5 seconds. Repeat 10 to 15 times (one set). Perform a total of three sets.

As your condition improves, perform straight leg raises with weights at the ankle; begin with a 2 pound weight and gradually increase to a 5 to 10 pound weight (pennies or fishing weights in an old sock, 2 cans in a purse, or Velcro ankle weights).

Hip abduction — Lie on your side on the bed or floor. The affected leg should be on top and should be held straight. The bottom leg should be bent. Hold the top leg straight and raise it 3 to 4 inches towards the ceiling. Hold for 5 seconds then slowly release. Repeat 10 to 15 times (one set). Perform a total of three sets.

Be sure to avoid rolling forwards or backwards while lifting the leg.

Hip adduction — Lie on your side on the bed or floor. The affected leg should be on bottom and should be held straight. The top leg should be bent with the foot placed in front of the bottom leg. Lift the bottom leg 3 to 4 inches. Hold for 5 seconds then slowly release. Repeat 10 to 15 times (one set). Perform a total of three sets.

Quarter squats — Stand 18 to 24 inches from a wall. Lean back against the wall. Bend both knees slightly (the buttocks should not be lower than the knees), keeping the back straight (picture 4). Hold for five seconds then slowly stand up straight. Rest as needed. Repeat 10 to 15 times (one set). Perform a total of three sets. To increase the difficulty, bend the knees more deeply, hold for a longer time, and increase the speed.

Alternately, use an exercise ball to perform squats. Stand up straight, holding the ball between your back and the wall. Slowly bend the knees and lower the back (roll the ball down the wall). Hold for a count of five. Stand up. Repeat 10 to 15 times.

Stretching exercises

Hamstring stretch — Sit on the floor or bed with the affected leg extended straight out in front of you. The opposite leg may be bent or may hang off the bed. Keeping the affected leg straight, lean forward and reach for the ankle. Hold for 30 seconds but do not bounce. Sit up straight. Repeat 10 to 15 times.

Quad stretch — Stand behind a chair, holding the top of the chair with one hand. Bend the knee and grab the foot with the hand on the same side of the body. Stand up straight. Gently pull the foot towards the body. Hold for 30 seconds, holding constant pressure on the foot (do not pull-release-pull). Release the foot. Repeat 10 to 15 times.

Runner's stretch — Face a wall and stand 18 to 24 inches away. Place hands at head height and lean into the wall, keeping legs and back straight. You can rest your head on your hands, against the wall. You should feel a stretch in the muscles in the back of the calf. Hold for 30 seconds. Repeat 10 to 15 times.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site ( Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces 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.

Patient information: Knee pain (The Basics)
Patient information: Bursitis (The Basics)
Patient information: Knee replacement (The Basics)
Patient information: Meniscal tear (The Basics)
Patient information: Muscle strain (The Basics)
Patient information: Patellofemoral pain syndrome (The Basics)
Patient information: Chondromalacia patella (The Basics)
Patient information: Iliotibial band syndrome (The Basics)
Patient information: Baker’s (popliteal) cyst (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient information: Bursitis (Beyond the Basics)
Patient information: Osteoarthritis symptoms and diagnosis (Beyond the Basics)
Patient information: Anterior cruciate ligament injury (Beyond the Basics)
Patient information: Nonsteroidal antiinflammatory drugs (NSAIDs) (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Anterior cruciate ligament injury
Clinical manifestations of rheumatoid arthritis
Clinical manifestations of osteoarthritis
General evaluation of the adult with knee pain
Knee bursitis
Medial collateral ligament injury of the knee
Meniscal injury of the knee
Overview of running injuries of the lower extremity
Patella fractures
Patellofemoral pain syndrome

The following organizations also provide reliable health information.

National Library of Medicine


American Academy of Orthopaedic Surgeons


National Institute of Arthritis and Musculoskeletal and Skin Disease


American College of Rheumatology


Arthritis Foundation


Literature review current through: Aug 2014. | This topic last updated: Jun 18, 2012.
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