Soft tissue lesions of the shoulder are usually caused by the narrowing of the subacromial or subcoracoid space and subsequent entrapment of soft tissues. These structural changes in the shoulder joint are often the result of overuse (e.g., repetitive overhead arm movements) and degenerative or inflammatory processes. The main symptom of soft tissue involvement is shoulder pain caused by impingement of soft tissue, most commonly of the supraspinatus tendon arm abduction over 60°. Further symptoms include nocturnal pain, pain on palpation, and stiffness of the joint. Chronic entrapment of the tendons can lead to tendinitis, which increases the risk of tendon rupture, especially of the rotator cuff tendons. Soft tissue injury of the shoulder is usually diagnosed clinically. Additional imaging tests (x-ray, MRI) can be used to determine the extent of damage. Management involves avoiding overhead activities, NSAIDs, and physical therapy. Intraarticular corticosteroid injections and surgical measures may be required in refractory cases.
- Injury of soft shoulder tissue, most commonly of the supraspinatus tendon, due to entrapment in the pathologically narrowed subacromial and/or subcoracoid space
- Most commonly involves the rotator cuff and subacromial bursa
- Overuse: activities involving repetitive overhead arm movement (e.g., basketball, volleyball)
- Degenerative processes (especially in older individuals)
- Diabetes mellitus
- Thyroid disease
- Dupuytren disease
- Iatrogenic: surgery (including from surgical implants in the subacromial space)
- Frequently associated with changes in adjacent structures, most commonly the following:
- Rotator cuff and scapular stabilizers
- Greater tubercle of the humerus or acromion (e.g., acromial spurs)
- Biceps tendon
- Joint capsule
- Acromial bursa
Subacromial impingement syndrome
- Definition: a clinical syndrome caused by compression of tissues around the glenohumeral joint (e.g., rotator cuff tendons, subacromial bursa) during shoulder abduction
Clinical features: Symptoms are most commonly due to supraspinatus injury or subacromial bursitis.
- Pain on movement that is worsened by overhead activities
- Painful arc and movement restriction depending on the muscle involved
- Nocturnal exacerbation of pain, especially when lying on the affected shoulder
- Fibrosis of the bursa
- Rupture of the rotator cuff, intermittent bursitis, and pseudoparalysis of the arm
- Rotator cuff tendinitis
- Rotator cuff tear (see “Complications” below)
Rotator cuff tendinitis
- Subacromial bursitis with peritendinitis of the rotator cuff
- Usually seen as a progression of subacromial impingement syndrome
- Subacromial tenderness on palpation
- Possibly atrophy of the supraspinatus and infraspinatus muscles
- See “Clinical features” in “Subacromial impingement syndrome” above.
- Complications: See “Rotator cuff tear” below.
Frozen shoulder (adhesive capsulitis)
- Definition: inflammation and fibrosis of the joint capsule leading to contracture of the shoulder joint
- Epidemiology 
Etiology: associated with diabetes mellitus, thyroid disorders (esp. hypothyroidism), shoulder injuries (e.g., rotator cuff tear, proximal humerus fracture), and
- Typically affects the nondominant shoulder
- Dull shoulder pain
Severe restriction of both active and passive range of motion of the glenohumeral joint in all planes, especially:
- External rotation
- Passive abduction (restricted to < 90°)
- Stages 
- Prognosis: self-limiting course (improvement typically takes > 1 year)
- Complications: atrophy of the deltoid and spinatus muscles
Calcific tendinitis is covered in detail in “BCP crystal deposition diseases.”
Pain and limited movement
- Subacromial pain triggered by manual exertion of pressure below the acromion
- Painful active and/or passive abduction, possibly aggravated by internal and/or external rotation
Signs of narrowed subacromial space and impingement
- Painful arc: pain with abduction of the arm between 60–120°
- Neer test
- See “Shoulder impingement tests”
- Signs of muscular or tendon involvement:
For detailed explanations of the clinical tests, see “Orthopedic shoulder examination.”
Subacromial lidocaine injection test 
- Helpful in distinguishing between subacromial impingement syndrome (including subacromial bursitis, rotator cuff tendinitis) and other causes of shoulder pain and restriction (e.g., complete rotator cuff tear, frozen shoulder, glenohumeral joint arthritis)
- Pain relief from injection suggests subacromial impingement syndrome.
- Low specificity (subacromial lidocaine injection improves pain in many conditions) but increases specificity of the Neer test 
X-ray to evaluate for:
- Degenerative changes or narrowing of the subacromial space (e.g., due to structural abnormalities of the acromion)
- Calcification of the supraspinatus tendon in calcifying tendinitis
- Alternative causes of shoulder pain (e.g., pathological fracture)
- X-ray is typically normal in frozen shoulder.
Ultrasound to evaluate for:
- Damage to the soft tissue structures (bursae, rotator cuff, and tendons)
- Bicep rupture, and subluxation or dislocation (e.g., acromioclavicular or glenohumeral joints)
- Provides more clinical information where there is diagnostic uncertainty or failure to respond to initial treatment
- Supports surgical planning
- Avoid activities involving overhead movement
- Antiinflammatory and analgesic medications (NSAIDs)
- Physical therapy: In frozen shoulder, gentle mobilization is followed by progressive exercises.
- Chronic pain may require subacromial glucocorticoid injections.
- Impingement: arthroscopic decompression, possibly open acromioplasty if evidence of acromion narrowing is apparent
- Rotator cuff tear: arthroscopic or open rotator cuff repair
- Removal of calcium deposits with ultrasound-guided needle lavage or extracorporeal shock wave therapy
Glucocorticoid injections can lead to tendon degeneration and should, therefore, be administered with restraint.
Rotator cuff tear
- Chronic degenerative tear is seen in individuals aged > 50 years.
- Acute injury is seen mostly in athletes (e.g., infraspinatus tear in baseball pitchers).
- Inflammation: a potential complication of rotator cuff tendinitis
- Most commonly affects the supraspinatus tendon
- Acute rupture: acute severe pain and loss of strength
- Degenerative rupture: chronic pain; loss of strength is less pronounced
- Restricted range of motion (depending on the muscle involved)
- Clinical diagnosis (see “Diagnostics” above)
- X-ray: superior displacement of the humeral head (high-riding humeral head)
- Ultrasound; and then possibly MRI to determine the location and extent of the rupture
- Treatment of degenerative tears is often conservative, especially in older and/or sedentary patients (see “Conservative treatment” above).
- Surgical repair; of the rotator cuff is recommended in patients with traumatic rupture, especially those who are physically active or who do not respond to conservative treatment.
We list the most important complications. The selection is not exhaustive.