Shoulder Pain

Definition: Pain referred to the shoulder is very common in the general population, particularly among the elderly. After back pain, it is the second most common acute musculoskeletal complaint in general practice. The prevalence of shoulder complaints among normal older persons is ~20%. With some forms of arthritis, such as RA, the prevalence of shoulder complaints exceeds 80%.

Anatomic Considerations: Pain described by patients as coming from the shoulder may originate from the joints (glenohumeral or acromioclavicular joints), periarticular structures (rotator cuff muscles, subacromial bursa, biceps tendon, etc). or may be referred from the neck (C-spine), chest (e.g., Pancoast tumor, angina), or abdomen (e.g., gallbladder, hepatic, diaphragmatic lesions). The shoulder is an incomplete ball-and-socket type of joint, and thus the shoulder is less stable than the hip, and is dependent on periarticular structures for support. The shoulder area defines a relatively narrow space through which many muscular, neurologic, and vascular structures must pass. Impingement of the rotator cuff, between the humeral head and the acromioclavicular arch, may occur with modest pathologic changes.

Etiology: Shoulder pain can derive from numerous structures in the area of the shoulder, including tendons, bursae, joints, nerves, ligaments, and muscles. Inciting stimuli for pain in these structures include inflammation, degeneration, trauma, and overuse.

The table lists the differential diagnosis of shoulder pain, amongst which rotator cuff disease is the most common and may account for 75% or more of patients with shoulder pain. Rotator cuff dysfunction represents a spectrum of severity, from rotator cuff tendinitis to rotator cuff tear to frozen shoulder.  Many patients have an associated subacromial bursitis.  Fibromyalgia frequently presents with focal shoulder pain, but on exam tends to be diffuse.

Differential Diagnosis of Shoulder pain
Bursitis/tendinitisRotator cuff dysfunction (including tendinitis, tendon tears, impingement syndrome, frozen shoulder)
Subacromial bursitis
Bicipital tendinitisArthritis (degenerative or inflammatory, e.g., rheumatoid arthritis, gout, spondyloarthropathy)

Glenohumeral arthritis

Acromioclavicular joint arthritis

Sternoclavicular joint arthritis

Bone disease

Fracture Dislocation/separation Metastatic cancer
Osteonecrosis (e.g., humeral head)

Neurologic/vascular

Suprascapular nerve entrapment
Thoracic outlet syndrome
Brachial plexus injury (brachial plexopathy)

Other (including referred pain)

Cervical spine disease

Polymyalgia rheumatica

Fibromyalgia
Reflex sympathetic dystrophy (also known as shoulder-hand syndrome)

Intrathoracic etiology (e.g., Pancoast tumor, myocardial infarction)

Intraabdominal etiology (e.g., perihepatitis, cholecystitis)

Cardinal Findings: A focused history and physical examination often succeed in defining the cause of shoulder pain. Shoulder pain from many causes may be exacerbated by activity. Classically, pain originating from the rotator cuff  is most prominent at night, and many patients report an inability to sleep on the affected shoulder. A history of trauma should raise suspicion of fracture or damage to periarticular structures. Acute shoulder pain may also result from acute bursitis or tendinitis from overuse or rotator cuff damage. Less commonly, septic, inflammatory, or crystal-induced arthritis may cause acute shoulder pain. Causes of chronic shoulder pain include rotator cuff dysfunction, overuse tendinitis, adhesive capsulitis, fibromyalgia, RA, and OA.

Testing for pain and range of motion on abduction, internal rotation, and external rotation of the humerus may establish rotator cuff dysfunction as the cause of the pain. Tenderness of the subacromial bursa will be apparent on direct palpation laterally below the acromion. Patients with glenohumeral arthritis often have substantial pain and resist active or passive/assisted movement of the shoulder joint. Arthritis of other joints about the shoulder (acromioclavicular, sternoclavicular) can be elicited on palpation. Neurovascular function should be tested to rule out those structures as the cause of shoulder pain.

Diagnostic Tests: Laboratory testing is seldom useful. If radiculopathy is being considered, then nerve conduction studies may be indicated.

Imaging: Plain radiography can be used to detect fracture or sequelae of arthritis. Standard views include an anteroposterior view and an anteroposterior view with external rotation. The glenohumeral joint can be assessed with and additional axillary view. MRI is well suited for the evaluation of  rotator cuff dysfunction specifically and shoulder pain in general. The accuracy of ultrasonography approaches that of MRI in detecting rotator cuff disease, synovitis, effusion, crystal arthritis and calcific tendinitis.

Therapy: The goal of treatment is to relieve pain and optimize function and range of motion. In many cases, temporary rest followed by physiotherapy to optimize range of motion is indicated. For treatment of pain, many patients respond to NSAIDs or simple analgesics. Local injection with corticosteroids may be of value in subacromial bursitis, bicipital tendinitis, or monarticular arthritis of the shoulder. Surgery is most often considered with severe rotator cuff dysfunction or impingement syndrome. Common procedures include excision of the distal clavicle or acromioplasty (for impingement syndrome), glenohumeral synovectomy (e.g., RA), or total shoulder arthroplasty (replacement).

Adapted from: RheumaKnowledgy