INTRODUCTION — Shoulder pain is a common musculoskeletal complaint that may be due either to intrinsic disorders of the shoulder or referred pain. The former include injuries and acute or chronic inflammation of the shoulder joint, tendons, surrounding ligaments, or periarticular structures [1].
An overview of common presentations and causes of shoulder discomfort and a basic clinical approach to diagnosis are reviewed. In-depth discussions of the shoulder examination and of the diagnosis and treatment of specific disorders of the shoulder are found separately. (See "Physical examination of the shoulder" and "Rotator cuff tendinopathy" and "Presentation and diagnosis of rotator cuff tears" and "Frozen shoulder (adhesive capsulitis)" and "Multidirectional instability of the shoulder" and "Glenohumeral osteoarthritis".)
ANATOMY AND BIOMECHANICS — A complex network of anatomic structures endows the human shoulder with tremendous mobility, greater than any other joint in the body. The shoulder girdle is composed of three bones (the clavicle, scapula, and proximal humerus) and four articular surfaces (sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic) (figure 1A-C). The glenohumeral joint, commonly referred to as the shoulder joint, is the principal articulation.
Glenohumeral structures — The glenohumeral joint is loosely constrained within a thin capsule bounded by surrounding muscles and ligaments (figure 1A-C and table 1). The shoulder's great mobility is due in large part to the shallow depth of the glenoid and the limited contact between the glenoid and the humeral head. Only 25 percent of the humeral head surface makes contact with the glenoid. The labrum, a fibrocartilaginous ring attached to the outer rim of the glenoid, provides some additional depth and stability. The shallowness and small surface area of the glenohumeral joint make it susceptible to instability and injury, and require that stability be provided primarily by extrinsic supports.
Surrounding muscles and ligaments provide these supports. The glenohumeral ligament serves as the primary static stabilizer. The rotator cuff serves as the primary dynamic stabilizer. The rotator cuff is composed of four muscles (supraspinatus, infraspinatus, subscapularis, and teres minor) that form a cuff around the head of the humerus, to which these muscles attach.
Shoulder pain is frequently caused by an acute or chronic injury of the rotator cuff, most often the supraspinatus muscle or tendon. The supraspinatus originates on the supraspinous fossa of the superior-posterior scapula, superior to the scapular spine, and inserts on the greater tubercle of the superior-lateral humeral head, just posterior to the biceps tendon. Proximal to its insertion it passes, along with the subacromial bursa, through the narrow space between the acromion process and the humeral head.
The acromion is a projection of the scapular spine that extends superiorly and anteriorly over the humeral head. Thus, with the shoulder in abduction, the supraspinatus is susceptible to impingement between the greater tubercle and the acromion. Activities involving repeated abduction with impingement can cause repetitive muscle and tendon trauma and ischemic compression of the tendon.
The sole, vital function of the subacromial bursa, also referred to as the subdeltoid bursa, is to lubricate and protect the rotator cuff tendons from the pressure and friction of the underside of the acromion.
Three other muscles contribute to the rotator cuff. The infraspinatus arises from the infraspinatus fossa of the posterior scapula and inserts on the lateral humeral head (greater tuberosity), just posterior to the supraspinatus where their insertions blend. The teres minor arises from the inferior-posterior scapula and blends with the infraspinatus to attach on the lateral humeral head (greater tuberosity). The subscapularis, the largest of the four cuff muscles, arises from the anterior scapula, inferior to the coracoid, and attaches to the anterior humeral head (lesser tuberosity).
The rotator cuff muscles rotate the humerus internally (subscapularis) and externally (infraspinatus primarily and teres minor), and contribute to abduction (supraspinatus), along with the deltoid muscle [2]. The deltoid is the most superficial muscle overriding the glenohumeral area, and it acts as the primary shoulder abductor. It arises from the acromion and attaches to the mid humerus.
The rotator cuff compresses the humoral head in the glenoid fossa, thereby stabilizing the glenohumeral joint, and serves to counterbalance the elevating forces of the deltoid, as well as the forces of other muscles acting on the humerus [3,4]. Weakness of the rotator cuff can lead to superior subluxation of the humeral head when the shoulder is abducted beyond 90 degrees, predisposing to impingement syndromes.
The suprascapular nerve innervates the supraspinatus and infraspinatus muscles. Suprascapular nerve injury causes a peripheral neuropathy that is estimated to account for one to two percent of pathologic shoulder conditions [5,6]. Injuries to the suprascapular nerve arise most often from mechanical compression by cysts or tumors. Suprascapular neuropathy causes pain, progressive atrophy, and weakened abduction and external rotation of the shoulder, and can be difficult to distinguish from rotator cuff tears.
Extraglenohumeral structures — Shoulder motion is also dependent upon the acromioclavicular (AC) and sternoclavicular (SC) joints and the scapulothoracic articulation (figure 1A-C). Together, they are capable of compensating significantly for decreased motion at the glenohumeral joint due to injury. The acromioclavicular joint is a common site of injury.
Coordination between glenohumeral and scapulothoracic motion is particularly important for shoulder function. Proper scapular motion and stability allows the humeral head to remain properly seated in the glenoid during abduction, provides a solid base from which the rotator cuff muscles can move the humerus, and enables proper elevation of the coracoacromial arch, thereby diminishing the risk of impingement syndrome (figure 2). The muscles primarily responsible for scapular stability and motion are the trapezius, serratus anterior, rhomboids, and levator scapulae.
The tendon of the long head of the biceps runs in the bicipital groove between the greater and lesser tubercles of the anterior proximal humerus. Transverse tendinous structures (either a continuation of the subscapularis tendon or a distinct transverse humeral ligament [7]) prevent subluxation of the tendon. Anterior shoulder pain can be caused by inflammation or injury to the biceps tendon.
Although the neural networks of the brachial plexus form proximally to the glenohumeral joint, the major peripheral nerves emanating from the plexus pass inferiorly to the joint. Pain from an injury to the plexus or related peripheral nerves from acute or chronic injury can present as shoulder pain. (See "Overview of upper extremity peripheral nerve syndromes".)
PATIENT HISTORY AND PAIN PATTERNS
General approach — Patients with acute shoulder pain often seek treatment following an episode of trauma. Diagnosis in this case can often be made by observation, gentle palpation, and x-ray. Next, the clinician must distinguish between extrinsic and intrinsic causes of shoulder pain. (See 'Stepwise clinical approach' below.) Once traumatic injury and potentially dangerous extrinsic causes have been excluded (table 2), the clinician is generally faced with one of several common patterns of shoulder pain, which are described below.
Patients experiencing a problem intrinsic to the shoulder present either with complaints of pain provoked by specific movement(s), stiffness or lack of flexibility, weakness or loss of function, instability, or a combination of these symptoms.
A standard pain history (ie, onset, duration, palliation/provocation, quality, location, and radiation) aids diagnosis. The clinician should inquire about activities that exacerbate symptoms either at work (eg, lifting overhead, painting) or leisure (eg, racquet sports, swimming). In addition, questions about previous injuries and treatment, including past surgery, and about comorbidities such as diabetes (increased risk of adhesive capsulitis) are important.
Anterolateral shoulder pain — Anterolateral shoulder pain aggravated by reaching overhead is a common pain pattern. It is often associated with impingement syndrome and the various stages of rotator cuff tendinopathy (simple strain, uncomplicated tendinopathy, chronic calcific tendinopathy, tendinopathy complicated by tear). Rotator cuff tendinopathy with tendon tear is suspected when pain is complicated by weakness and a notable loss of strength in external rotation or abduction (a loss that is not attributable to poor effort). Adhesive capsulitis (ie, frozen shoulder) is the most likely diagnosis when pain is accompanied by stiffness and a significant loss of movement in external rotation or abduction. Labral tears may present with anterolateral pain, although pain may be deep and poorly localized, and may be associated with instability and a catching sensation.
Conditions affecting the acromioclavicular (AC) joint, such as AC separation, if trauma has occurred, or osteoarthritis, are suspected when pain is well localized (the patient often uses one finger to point to the end of the clavicle). Involvement of the glenohumeral joint is suspected when pain is aggravated by movement in multiple directions. Pain originating from the tendon of the long head of the biceps can create well-localized anterior shoulder pain aggravated by lifting or carrying objects like shopping bags.
Posterior shoulder pain — Posterior shoulder pain is the least common pattern of the intrinsic conditions affecting the shoulder. Rotator cuff tendinopathy involving the external rotators (teres minor and infraspinatus) can cause focal pain, or sometimes referred pain over the scapula. More diffuse pain over the general area of the superior trapezius can be referred from the cervical spine (cervical strain or radiculopathy).
Poorly localized pain — Pain that is poorly localized or vaguely described is often extrinsic. Cervical nerve root impingement can produce sharp pain radiating from the neck into the posterior shoulder area and arm. Shoulder pain can be referred from the neck or abdomen, results from a compression neuropathy, or arises from the bone (table 2). Poorly localized shoulder pain in the setting of a normal shoulder examination should raise concern for intraabdominal or other extrinsic pathology. Although uncommon, elbow pathology may refer to the shoulder.
Shoulder pain may also reflect psychological overtones of cases under litigation or malingering, however, such diagnoses should be entertained only after true pathology has been ruled out. Intrinsic pathology may cause poorly localized pain. Examples include large rotator cuff tears and avascular necrosis of the humoral head. A large Finnish survey found nonspecific shoulder complaints without clinical findings to correlate with depressive illness and not to correlate with rotator cuff tendinopathy [8].
Trauma — Fractures and dislocations of the shoulder often occur as a result of blunt trauma. Falls directly onto the shoulder can cause acromioclavicular separation. (See "Acromioclavicular joint injuries".) Falls or direct blows can cause a clavicle fracture. Falls onto an outstretched arm are the most common cause of proximal humerus fractures. Blunt trauma and, less often, violent muscular contractions, such as those that occur with generalized seizures, can cause glenohumeral dislocations. Generally, the patient can localize pain to the site of injury, and deformity may be present. Post-traumatic shoulder pain can also be referred from intraabdominal injuries causing diaphragmatic irritation (eg, bleeding from liver or spleen).
Sometimes patients present several weeks or months following an injury. Pain may cause the patient not to use the shoulder in the interim leading to adhesive capsulitis. (See 'Adhesive capsulitis' below.)
ETIOLOGY — The majority of patients who present to primary care clinics with shoulder pain have an intrinsic disorder. Acute symptoms (less than two weeks duration) in patients with a history of recent shoulder trauma are typically due to an acromioclavicular (AC) separation, glenohumeral dislocation, fracture, or rotator cuff tear [9]. In addition to pain, patients may complain that the shoulder is discolored, deformed, or swollen. Significant medical problems, however, such as cardiac ischemia, hepatobiliary disease, and intraabdominal injury, can present with referred shoulder pain (table 2).
Patient age — In addition to location (see 'Patient history and pain patterns' above), several other historical factors can help to differentiate among the intrinsic causes of shoulder pain. Patient age is one such factor (table 3):
- Sports injuries due to overuse ("muscular strain") and subluxation of the glenohumeral joint are most common in adolescents and young adults [9]. "Shoulder separation," due to a sprain of the acromioclavicular ligaments, is also more common in younger patients. It is seen following a fall, with the arm adducted, directly onto the acromion, commonly referred to as the point or tip of the shoulder. (See "Acromioclavicular joint injuries".)
- Middle-aged and older individuals more often develop shoulder pain due to rotator cuff lesions, such as supraspinatus tendinopathy and partial or full-thickness tendon tears [10,11].
- Frozen shoulder syndrome and symptomatic osteoarthritis also occur predominately in older patients. Bilateral shoulder involvement, also more common among older patients, suggests an inflammatory process such as polymyalgia rheumatica or rheumatoid arthritis, or rarely hyper or hypothyroidism.
Rotator cuff injury — Rotator cuff injury is among the most common causes of shoulder pain. The rotator cuff tendons, particularly the supraspinatus tendon, are uniquely susceptible to the compressive forces of subacromial impingement (see 'Anatomy and biomechanics' above) and dominate the conditions affecting the shoulder, especially in patients over the age of 30 [12]. Improper athletic technique, poor muscular conditioning, poor posture, and failure of the subacromial bursa to protect adequately the supporting tendons may result in a progression of injury from acute inflammation, to calcification, to degenerative thinning, and finally to tendon tear. (See "Rotator cuff tendinopathy" and "Presentation and diagnosis of rotator cuff tears".)
Impingement syndrome — Impingement syndrome is the term used to describe symptoms and signs that result from compression of the rotator cuff tendons and the subacromial bursa between the greater tubercle of the humeral head and the lateral edge of the acromion process [13].
The symptoms of impingement syndrome are nearly identical to those of rotator cuff tendinopathy (see 'Tendinopathy' below). Overhead reaching and positioning cause pain over the outer deltoid. Atrophy of the muscles around the top and back of the shoulder may be apparent if symptoms are longstanding. Crepitus may be felt with attempts to abduct the arm beyond 60 degrees. Patients with rounded shoulders (a down-sloping acromial angle), poor muscular development, and occupations that require repetitive work at or above the shoulder are at greatest risk. (See "Shoulder impingement syndrome".)
Tendinopathy — Rotator cuff tendinopathy almost always represents chronic injury to the supraspinatus (abduction) and/or infraspinatus (external rotation) tendons. Tendinopathy usually develops as a consequence of repetitive activity, generally at or above shoulder height, which leads to tendon degeneration and microvascular insult.
Patients complain of shoulder pain aggravated by reaching, pushing, pulling, lifting, positioning the arm above the shoulder level, or lying on the affected side. Most patients do not describe an injury or fall. The patient typically places the hand over the outer deltoid, rubbing the muscle in an up-and-down direction when describing the pain. Common shoulder tendinopathy must be distinguished from frozen shoulder (loss of range of motion), rotator cuff tendon tear (persistent weakness), and biceps tendinopathy (painful arm flexion). (See "Rotator cuff tendinopathy".)
Tendon tear — Rotator cuff tendon tears (ie, loss of the normal integrity of the supraspinatus tendon, the infraspinatus tendon, or both) occur as the end result of chronic subacromial impingement, progressive tendon degeneration, traumatic injury, or a combination of these factors. Tears occur primarily in the supraspinatus tendon. (See "Presentation and diagnosis of rotator cuff tears".)
Patients complain of shoulder weakness, pain over the anterolateral shoulder, or sometimes the upper back, and a popping or catching sensation when the shoulder is moved. Night pain is common and often affects sleep because the patient is unable to keep the arm in a position that does not elicit pain (ie, adducted without rotation).
Injuries most commonly associated with acute rotator cuff tendon tears include falls onto the outstretched arm, falls directly onto the outer shoulder, vigorous pulling (such as on a lawn mower cable), and unusual heavy pushing and pulling. Acute, subacute, and chronic tears all occur most often in patients over the age of 40 with a history of impingement [10,11].
Shoulder function will be preserved if the tear parallels the direction of the tendon fibers or is small in size, and the patient will complain only of shoulder pain, pain with direct pressure, and pain aggravated by active reaching, lifting, pushing, and pulling. However, if the tear is large, affecting both the supraspinatus and infraspinatus tendons, and is transverse in direction (total interruption of the tendon with muscle retraction), the patient will complain of weakness, the typical symptoms of tendinopathy, and dramatic loss of function — an inability to reach overhead, lift with an outstretched arm, and an impairment of pushing and pulling.
Labral tear — Many of the same mechanisms that produce rotator cuff injury can also produce tears of the labrum. Athletes who engage in repetitive overhead activities that load the shoulder (eg, baseball pitching, tennis serving, swimming) are at greater risk for such injuries. Symptoms include deep shoulder pain, catching sensation, instability, and crepitus.
Adhesive capsulitis — Adhesive capsulitis (commonly referred to as frozen shoulder) refers to a stiffened glenohumeral joint that has lost significant range of motion (abduction and rotation). It is a reversible contraction of the joint capsule in almost all cases. (See "Frozen shoulder (adhesive capsulitis)".) Any shoulder pain or disability that causes the patient not to use his or her shoulder can lead to diminished joint mobility and ultimately adhesive capsulitis.
The most common cause is rotator cuff tendinopathy. Diabetes mellitus also puts patients at significantly increased risk of developing adhesive capsulitis [14-16]. Other diseases that increase the risk for frozen shoulder, most likely due to immobility, include stroke, Parkinson disease, and chronic pulmonary disease. Low pain tolerance, poor compliance with exercise therapy, and immobilization in a sling (eg, for treatment of a shoulder or elbow injury) can also contribute to the development of a frozen shoulder.
While the symptoms and signs of adhesive capsulitis and rotator cuff tendinopathy overlap, presentation often differs. Patients with adhesive capsulitis complain primarily of stiffness, although they may have pain, and always demonstrate diminished passive range of motion. Patients with rotator cuff tendinopathy typically complain of pain with active motion, while passive motion remains normal (in the absence of guarding). The loss of motion associated with a frozen shoulder causes various degrees of impaired function, including limited reaching (eg, overhead, across the chest) and limited rotation (eg, unable to scratch the back, difficulty putting on a coat). Patients with rotator cuff tendinopathy suffer similar restrictions, but their limitations are due more to pain than an absolute loss of movement. Patients with either condition may experience increased pain at night either from direct pressure or shoulder movement.
Acromioclavicular pain — The acromioclavicular (AC) joint is another common site of pathology in patients with shoulder complaints. The joint is susceptible to arthritic change and trauma ("shoulder separation"). (See "Acromioclavicular joint injuries".)
Patients complain of anterior shoulder pain, deformity, or both and often point to the AC joint when describing their symptoms. Patients with osteoarthritis may describe a grinding or popping sensation when reaching overhead or across the chest. The adduction part of the Apley scratch test can elicit this sign. Patients with an acute separation usually relate a history of falling directly onto the shoulder. Those with second and third-degree sprains typically have a palpable step-off deformity at the AC joint. They often hold their arm close to the chest and resist rotation and elevation.
Biceps tendinopathy/rupture — Biceps tendinopathy is an inflammation of the long head of the biceps tendon as it passes through the bicipital groove of the anterior proximal humerus. Repetitive lifting and to a lesser extent, overhead reaching, leads to inflammation, micro-tearing, and if untreated, degenerative change. Unusual or vigorous lifting in the setting of a chronically inflamed tendon can lead to spontaneous rupture. (See "Biceps tendinopathy and tendon rupture".)
The patient complains of anterior shoulder pain aggravated by lifting, carrying objects like shopping bags, and overhead reaching. A dramatic worsening of symptoms and description of a lump just above the antecubital fossa suggests an acute long head tendon rupture. Weakness is most often attributed to the pain of active tendinopathy. Rupture of the long head of the biceps rarely is associated with significant weakness; the brachioradialis and the short head of the biceps account for 80 to 85 percent of the strength of elbow flexion.
Multidirectional shoulder instability — Multidirectional instability of the shoulder is synonymous with "subluxation," "loose" shoulder, or partial dislocation. It is more common in young women with poor muscular development, patients with large rotator cuff tendon tears (loss of muscular support), and in athletes under the age of 40, especially swimmers and throwers. The symptoms are often vague and nonspecific ("dead arm," looseness, or crepitation) unless the condition is complicated by rotator cuff tendinopathy. Typically the patient has an excessive range of motion, particularly with internal and external rotation. (See "Multidirectional instability of the shoulder".)
Glenohumeral osteoarthritis — Osteoarthritis of the glenohumeral joint represents wear-and-tear of the articular cartilage of the glenoid, labrum, and humeral head. It is an uncommon problem that is generally preceded by trauma, although the injury may have occurred years earlier. Injuries that are associated with the development of osteoarthritis include previous dislocation, humeral head or neck fracture, large rotator cuff tendon tears (loss of musculotendinous support), and rheumatoid arthritis. Patients complain of the gradual development of anterior or deep shoulder pain and stiffness over a period of months to years. Both active and passive motion, particularly abduction and external rotation, become diminished as articular degeneration grows more severe. (See "Glenohumeral osteoarthritis".)
Because osteoarthritis of the shoulder is so rare, clinicians should also consider the possibility of metabolic disease (eg, hemochromatosis) as a cause.
Scapular instability — Weakness of the muscles that stabilize the scapula predisposes the patient to impingement syndrome. (See 'Anatomy and biomechanics' above.)
Although a difficult diagnosis to make, scapular instability may manifest with abnormal shoulder motion, shoulder weakness, or mild scapular winging in patients with symptoms suggestive of rotator cuff pathology. Improvement of abduction strength when performed while the scapula is stabilized by the examiner suggests weakness of the scapula stabilizers. Less commonly, nerve injury can cause winging of the scapula. (See "Overview of upper extremity peripheral nerve syndromes", section on 'Proximal neuropathies'.)
Scapulothoracic bursitis — Scapulothoracic (subscapular) bursitis may result from mechanical pressure and friction, most often between the superior-medial angle of the scapula and the adjacent second and third ribs. Poor muscular development in thin patients, kyphotic posture, repetitive to-and-fro motion of the scapula (ironing, assembly work, throwing sports), and direct pressure are common causes.
Affected patients complain of localized pain over the upper back or a popping sound whenever the shoulder is shrugged. A typical patient has poor muscular development, an asthenic physique, and poor posture.
Referred pain — Referred pain to the shoulder may be seen in a variety of clinical settings:
A distinguishing characteristic of referred pain, in contrast to intrinsic shoulder problems, is that shoulder movement is normal and does not alter the character of the pain. A careful history can often distinguish among the causes of referred shoulder pain.
EXAMINATION — Examination of the shoulder is guided by the history. Although some components of the examination, such as inspection and a basic neurovascular evaluation are universal, other components are performed selectively based upon the diagnoses being entertained. A framework for determining when to perform specific maneuvers is provided in the shoulder pain algorithm and the section on clinical evaluation below. (See 'Stepwise clinical approach' below.)
As noted, shoulder anatomy and motion are complex, and thus, the examination of the shoulder is also complex, with many maneuvers to assess different aspects of shoulder function. The performance of the shoulder examination is discussed detail separately. (See "Physical examination of the shoulder".)
STEPWISE CLINICAL APPROACH — For many primary care clinicians, determining how best to evaluate patients with shoulder pain can be difficult. The anatomy of the shoulder is complex and the differential diagnosis broad. Fortunately, patients with shoulder pathology most often present in stereotypical fashion. By following the basic approach outlined here (algorithm 1), clinicians should be able to diagnose and either manage or refer appropriately the great majority of patients with shoulder complaints.
Step one: Traumatic versus nontraumatic — The first step is to determine whether a traumatic injury is present. Most often this determination is straightforward based on the patient's history, although delayed presentations do occur, for example, with mild acromioclavicular (AC) separations. Examination may reveal deformity, and the patient is nearly always able to localize the pain. Plain x-rays make or confirm the diagnosis.
The most common shoulder injuries from minor blunt trauma include: fractures of the clavicle and proximal humerus, dislocations of the glenohumeral joint, and sprains of the AC joint.
Should x-rays fail to reveal an injury but the patient's symptoms persist, a soft tissue injury (eg, rotator cuff tear) is likely and the clinician should perform an appropriate assessment (step three below).
Step two: Extrinsic versus intrinsic — Once traumatic injury has been excluded, the second step is to determine whether the patient's shoulder pain is a referred symptom caused by pathology extrinsic to the shoulder (table 2), or intrinsic. A careful history and preliminary examination should enable the clinician to make this distinction. Often, if the cause is extrinsic, the patient has difficulty localizing the pain. The pain itself is often vague if it is referred from a thoracic or abdominal source, or sharp with radiation if it is from a neurologic source.
The history may reveal details or associated symptoms of concern:
- Cervical nerve root impingement may be present in the patient with sharp pain radiating from the neck into the posterior shoulder area or arm.
- Splenic injury may be present in the patient with shoulder pain recently involved in an automobile accident in which the shoulder was not initially injured.
- Myocardial ischemia may be present in the patient who experiences diaphoresis or dyspnea with each episode of shoulder pain.
Examination of patients with an extrinsic cause of shoulder pain most often reveals painless range of motion and no asymmetry in appearance, motion, or strength when compared with the opposite shoulder.
Step three: Glenohumeral versus extraglenohumeral — If an intrinsic problem is present, the clinician must next determine whether its focus is the glenohumeral joint or not. Generally the patient is able to localize the pain from extra-glenohumeral pathology to a specific site, such as the bicipital groove for biceps tendinopathy, or the acromioclavicular (AC) joint for AC osteoarthritis. Weakness of the stabilizing muscles of the scapula is a notable exception, and this diagnosis can be difficult to make. A careful assessment of scapulothoracic motion and observation for any scapular winging can aid diagnosis.
In all cases of extra-glenohumeral pathology, passive range of motion of the glenohumeral joint should be normal, although assessment may be limited by pain or guarding. With problems related directly to the glenohumeral joint and its surrounding structures, examination should reveal some abnormality, be it pain, weakness, or abnormal motion.
Step four: Differentiating glenohumeral pathology — Once extra-glenohumeral pathology has been ruled out, the clinician must try to determine which of several glenohumeral abnormalities is causing the patient's symptoms. Assessment of shoulder range of motion, strength, and signs of impingement will help to distinguish among such diagnoses as rotator cuff tendinopathy, rotator cuff tear, and adhesive capsulitis. A summary of the key examination findings for each common diagnosis is found immediately below. Further detail about the shoulder examination is found separately (table 4). (See "Physical examination of the shoulder".)
- Impingement and rotator cuff tendinopathy – Anterolateral shoulder pain that increases with overhead reaching; pain with supraspinatus testing and/or external rotation; positive impingement tests
- Rotator cuff tendon tear – Older patient (age >40); pain and weakness with supraspinatus testing and/or external rotation; positive impingement tests
- Adhesive capsulitis – History of diabetes or immobilizing disability (eg, stroke, injury requiring sling); diminished active and passive range of motion
- Glenohumeral osteoarthritis – History of shoulder trauma; pain; diminished active and passive range of motion; x-ray shows sclerosis and diminished joint space
- Multidirectional shoulder instability – Younger patient (age <40); positive sulcus sign; positive instability test
INJECTION TESTS — When the examination suggests the presence of a specific disorder, certain tests can be performed to confirm the diagnosis.
Lidocaine injection test — The lidocaine injection test is used to (picture 1):
- Exclude glenohumeral joint involvement
- Confirm rotator cuff tendinopathy
- Exclude rotator cuff tear
- Determine the degree of frozen shoulder
Patients with a rotator cuff tear will have persistent weakness despite pain relief with injection, while those with rotator cuff tendinopathy will have normal strength in association with pain relief. Patients with a frozen shoulder will have persistent loss of range of motion. Dramatic reduction in pain and improvement in overall shoulder function after injection of the subacromial bursa effectively rules out a significant glenohumeral joint process.
The lidocaine injection test in the subacromial bursa is indicated when the history and physical examination cannot effectively exclude an underlying rotator cuff tendon tear, a developing frozen shoulder, or concurrent involvement of the acromioclavicular (AC) joint.
Local anesthetic block at the bicipital groove — Bicipital tendinopathy can be confirmed by local anesthetic block (picture 2). This is most often indicated in the patient presenting with anterior shoulder pain with an equivocal physical examination demonstrating signs of bicipital tendinopathy and rotator cuff tendinopathy, especially involving the subscapularis tendon (an internal rotator and adductor of the shoulder).
RADIOGRAPHIC STUDIES — Diagnostic imaging of the shoulder may be valuable when directed by the history and physical examination. A variety of modalities may be employed. A complete discussion of these studies is found elsewhere. (See "Radiologic evaluation of the painful shoulder".)
Plain radiographs — Plain radiographs of the shoulder generally have limited benefit in the evaluation of nontraumatic shoulder pain. This was illustrated in a study of 312 patients seen in an emergency department setting for shoulder pain: only 37 of the 185 shoulder films (20 percent) were therapeutically informative, ie, identified conditions requiring specific therapy, such as a fracture or dislocation [17]. No patient without a shoulder deformity or a precipitating fall had an informative radiograph.
A subsequent study of 206 patients used the presence or absence of the following features: history of falling, swelling, rest pain, abnormalities in range of motion, and obvious deformities of the shoulder, to help identify those in whom a shoulder radiograph was unlikely to be informative [18]. Among those without obvious shoulder deformities and swelling, the following three groups had relatively insignificant radiographs:
- Patients without rest pain who had fallen. No significant radiographic findings were found among 18 patients with these features.
- Patients who had fallen, had rest pain, and had normal range of motion. No therapeutically informative radiographs were reported in 10 such patients.
- Patients who had not fallen. Only 1 of 107 such patients had a lytic lesion discovered on radiograph; this individual was already known to have multiple myeloma.
While there are no specific guidelines for when radiography is indicated, we generally recommend obtaining plain films in patients who have lost range of motion, particularly when there is severe pain, and after trauma. Plain films can identify the following:
- Fractures of the proximal humerus, clavicle, and scapula
- Glenohumeral dislocations
- Glenohumeral osteoarthritis (picture 3)
- Acromioclavicular (AC) joint arthritis or injury (picture 4)
- Sternoclavicular (SC) joint arthritis (apical lordotic views of the chest)
In addition, indirect evidence of rotator cuff thinning, tear, or both may be evident on plain x-ray of the shoulder (picture 5). A subacromial space measurement less than 1 cm suggests thinning with or without tear, which can be confirmed by MRI.
When plain films are obtained in a patient with a history of trauma, both AP and axillary views are warranted since some conditions can be missed on the former alone.
Magnetic resonance imaging — MRI is the preferred imaging study for patients with suspected impingement and rotator cuff injury. A normal MRI suggests that the likelihood of a rotator cuff tear is less than 10 percent [19-21]. On the other hand, MRI findings for rotator cuff tears are not highly specific, particularly in older patients [22]. The sensitivity and specificity of MRI for the diagnosis of impingement are approximately 93 and 87 percent, respectively [23]. MRI is also useful in the evaluation of avascular necrosis, biceps tendinopathy and rupture, inflammatory processes, and tumors [24].
Ultrasonography — In the hands of skilled operators, the diagnostic accuracy of ultrasound has been found to be the equivalent of MRI in identifying rotator cuff tears, labral tears, and biceps tendon tears and dislocations [25-31]. Ultrasound is less expensive than MRI and preferred by patients [31,32].
Arthrography — Arthrography has largely been replaced by MRI for the diagnosis of rotator cuff disorders. It is specific for rotator cuff tears, but it has a low sensitivity since it cannot detect partial-thickness tears nor associated soft tissue injuries [33]. Arthrography still may be useful for evaluating frozen shoulder and may even be therapeutic. (See "Frozen shoulder (adhesive capsulitis)".)
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.)
SUMMARY AND RECOMMENDATIONS
- A complex network of anatomic structures endows the human shoulder with tremendous mobility, which can make examination and diagnosis challenging. The shoulder girdle is composed of three bones (the clavicle, scapula, and proximal humerus), four articular surfaces (sternoclavicular, acromioclavicular, glenohumeral, and scapulothoracic), and soft tissues (eg, rotator cuff muscles) (figure 1A-C). (See 'Anatomy and biomechanics' above and "Physical examination of the shoulder".)
- Patients with acute shoulder pain often seek treatment following an episode of trauma. Diagnosis in this case can often be made by observation, gentle palpation, and x-ray. Next, the clinician must distinguish between extrinsic and intrinsic causes of shoulder pain. Once traumatic injury and potentially dangerous extrinsic causes have been excluded (table 2), the clinician is generally faced with one of several common patterns of shoulder pain, which are described in the text. (See 'Patient history and pain patterns' above.)
- Traumatic causes of shoulder pain include fracture and soft tissue injury. Acute symptoms (less than two weeks duration) in patients with a history of recent shoulder trauma are typically due to an acromioclavicular (AC) separation, glenohumeral dislocation, fracture, or rotator cuff tear. (See 'Trauma' above.)
- Significant internal pathology, including cardiac ischemia, hepatobiliary disease, and intraperitoneal bleeding, may manifest with referred shoulder pain. (See 'Poorly localized pain' above and 'Referred pain' above.)
- Anterolateral shoulder pain aggravated by reaching overhead is a common pain pattern. It is often associated with impingement syndrome and the various stages of rotator cuff tendinopathy. Adhesive capsulitis (ie, frozen shoulder) is the most likely diagnosis when pain is accompanied by stiffness and a significant loss of movement in external rotation or abduction. (See 'Anterolateral shoulder pain' above and 'Rotator cuff injury' above and 'Labral tear' above and 'Adhesive capsulitis' above.)
- Pain that is poorly localized or vaguely described is often extrinsic. Cervical nerve root impingement can produce sharp pain radiating from the neck into the posterior shoulder area and arm.
- Patient age and activity are important factors to consider when considering the differential diagnosis of shoulder pain (table 3). (See 'Etiology' above.)
- A stepwise clinical approach to the patient with shoulder complaints is described in the text (algorithm 1). (See 'Stepwise clinical approach' above.)
- Diagnostic imaging of the shoulder may be valuable when directed by the history and physical examination. The best modality to use depends upon the history and clinical findings. (See 'Radiographic studies' above.)
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