Shoulder pain

Shoulder pain is a common clinical complaint that can arise from a wide range of musculoskeletal, neurological, or systemic conditions. It affects daily activities, occupational performance, and overall quality of life. Early assessment and management are crucial to prevent chronic disability.

Anatomy of the Shoulder

Bony Structures

The shoulder complex is composed of several bones that contribute to its wide range of motion and functional stability:

• Clavicle: Connects the upper limb to the trunk via the sternoclavicular joint and provides leverage for shoulder movements.
• Scapula: Serves as the attachment site for multiple muscles and articulates with the humerus at the glenoid fossa.
• Humerus: The proximal humerus forms the ball of the glenohumeral joint.
• Joints: Glenohumeral joint, acromioclavicular joint, and sternoclavicular joint allow mobility and stability of the shoulder complex.

Muscles and Tendons

The shoulder’s mobility and stability are maintained by several muscles and their tendinous attachments:

• Rotator cuff muscles: Supraspinatus, infraspinatus, teres minor, and subscapularis stabilize the glenohumeral joint.
• Deltoid: Responsible for arm abduction and contributes to shoulder contour.
• Biceps brachii: Assists in flexion and supination of the forearm, with its long head tendon passing through the bicipital groove.
• Trapezius and Pectoralis major: Support scapular motion and shoulder positioning.

Ligaments and Capsule

The shoulder joint is stabilized by both ligamentous structures and the joint capsule:

• Glenohumeral ligaments provide anterior and inferior stability.
• Coracoacromial and coracoclavicular ligaments reinforce the acromioclavicular joint.
• The joint capsule envelops the glenohumeral joint, allowing flexibility while maintaining joint integrity.

Bursae

Bursae reduce friction between moving structures of the shoulder:

• Subacromial-subdeltoid bursa: Located beneath the acromion and deltoid, it facilitates smooth gliding of the rotator cuff tendons.
• Other minor bursae exist around the acromioclavicular and subscapular regions to prevent friction between tendons and bones.

Physiology and Biomechanics

The shoulder complex allows a wide range of movements while maintaining stability through coordinated muscular and ligamentous actions.

Normal Range of Motion

• Flexion: 0 to 180 degrees
• Extension: 0 to 60 degrees
• Abduction: 0 to 180 degrees
• Adduction: 0 to 50 degrees
• Internal rotation: 0 to 70 degrees
• External rotation: 0 to 90 degrees

Muscle Coordination and Stabilization

Dynamic stability is achieved through the coordinated action of the rotator cuff muscles, deltoid, and scapular stabilizers. These muscles maintain the humeral head centered in the glenoid fossa during motion and prevent subluxation.

Load Distribution and Functional Mechanics

The shoulder distributes forces generated during lifting, pushing, or throwing activities. Proper scapulothoracic and glenohumeral mechanics are essential to prevent overuse injuries and maintain efficient motion patterns.

Etiology of Shoulder Pain

Acute Causes

• Trauma: Fractures of the clavicle, scapula, or proximal humerus, and shoulder dislocations resulting from falls or direct impact.
• Rotator cuff tears: Sudden tears caused by heavy lifting, sports injuries, or accidents.

Chronic Causes

• Tendinopathy: Degenerative changes or inflammation of the rotator cuff or biceps tendon due to repetitive overhead activities.
• Bursitis: Inflammation of the subacromial or subdeltoid bursa leading to pain and restricted motion.
• Osteoarthritis: Degenerative joint disease affecting the glenohumeral or acromioclavicular joints.
• Frozen shoulder (adhesive capsulitis): Progressive stiffness and pain due to capsular fibrosis.

Referred Pain

• Cervical spine pathology: Radiculopathy or nerve compression can mimic shoulder pain.
• Cardiac or diaphragmatic origin: Myocardial ischemia or subdiaphragmatic issues may present as shoulder discomfort.

Inflammatory and Systemic Causes

• Rheumatoid arthritis: Autoimmune inflammation affecting the glenohumeral or acromioclavicular joints.
• Polymyalgia rheumatica: Inflammatory condition causing proximal muscle pain including the shoulders.
• Infection: Septic arthritis or osteomyelitis involving shoulder structures.

Clinical Presentation

History

A detailed patient history helps narrow the differential diagnosis of shoulder pain:

• Onset, duration, and progression of pain.
• Aggravating and relieving factors, including activity-related triggers.
• History of trauma, repetitive motion, or occupational hazards.
• Associated symptoms such as numbness, weakness, or systemic signs.

Physical Examination

Clinical evaluation involves inspection, palpation, and functional testing:

• Inspection: Assess for swelling, deformity, muscle atrophy, or abnormal posture.
• Palpation: Identify tenderness over bones, muscles, tendons, and bursae.
• Range of Motion Assessment: Active and passive movements to detect limitations and pain patterns.
• Special Tests: Tests for rotator cuff integrity, impingement, and shoulder instability such as Neer, Hawkins-Kennedy, and apprehension tests.

Diagnostic Evaluation

Imaging

Imaging studies are essential to identify structural abnormalities contributing to shoulder pain:

• X-ray: Evaluates bone fractures, dislocations, degenerative changes, and calcifications.
• MRI: Assesses soft tissue injuries including rotator cuff tears, labral lesions, and bursitis.
• CT scan: Provides detailed bony anatomy, useful for complex fractures or preoperative planning.
• Ultrasound: Dynamic evaluation of tendons, bursae, and muscle movement.

Laboratory Tests

Laboratory investigations help identify inflammatory or infectious causes:

• Complete blood count and inflammatory markers such as ESR and CRP.
• Rheumatologic panels for autoimmune conditions like rheumatoid arthritis.
• Cultures if infection is suspected.

Electrodiagnostic Studies

Nerve conduction studies and electromyography may be indicated when cervical radiculopathy or peripheral neuropathy is suspected as a source of referred shoulder pain.

Management of Shoulder Pain

Conservative Treatment

Initial management often involves non-invasive strategies:

• Rest and activity modification to prevent aggravation.
• Physical therapy including stretching, strengthening, and range of motion exercises.
• Pharmacologic interventions such as nonsteroidal anti-inflammatory drugs or analgesics for pain relief.

Interventional Procedures

When conservative measures are insufficient, targeted procedures may be used:

• Corticosteroid injections into the subacromial space or glenohumeral joint to reduce inflammation.
• Biologic injections such as platelet-rich plasma for tendon healing in selected cases.

Surgical Treatment

Surgery is reserved for severe structural lesions or failure of conservative therapy:

• Arthroscopic procedures for rotator cuff repair, labral repair, or subacromial decompression.
• Open surgery for complex fractures or shoulder instability.
• Shoulder arthroplasty (partial or total) for end-stage arthritis or irreparable rotator cuff damage.

Prevention and Rehabilitation

Ergonomic and Activity Modification

Preventing shoulder pain involves minimizing strain and optimizing shoulder mechanics during daily activities and work-related tasks:

• Adjusting workstations to maintain neutral shoulder positions.
• Using proper lifting techniques to avoid overloading the shoulder.
• Avoiding repetitive overhead movements when possible.

Strengthening and Flexibility Exercises

Targeted exercises help maintain shoulder stability and reduce the risk of injury:

• Rotator cuff strengthening to support the glenohumeral joint.
• Scapular stabilizer exercises to improve shoulder mechanics.
• Stretching exercises to maintain flexibility of the joint capsule and surrounding musculature.

Postoperative and Injury Rehabilitation Protocols

Rehabilitation following surgery or injury is critical for restoring function and preventing recurrence:

• Gradual progression of range of motion exercises.
• Strengthening exercises once healing allows.
• Functional training to return to daily activities or sports.

Prognosis and Outcomes

Factors Affecting Recovery

The prognosis of shoulder pain depends on multiple factors:

• Severity and type of underlying pathology.
• Timeliness and adequacy of treatment.
• Patient age, comorbidities, and adherence to rehabilitation protocols.

Long-term Functional Outcomes

With appropriate management, most patients regain satisfactory shoulder function. Outcomes vary according to the extent of structural damage and effectiveness of rehabilitation.

Recurrence and Chronic Pain Management

Some patients may experience recurrent or chronic shoulder pain due to degenerative changes, incomplete healing, or ongoing biomechanical stress. Long-term management strategies include:

• Regular exercise to maintain strength and flexibility.
• Modification of activities that aggravate symptoms.
• Periodic medical review for early detection of recurrent or progressive pathology.

References

1. Standring S. Gray’s Anatomy. 42nd ed. London: Elsevier; 2020.
2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2018.
3. Netter FH. Atlas of Human Anatomy. 7th ed. Philadelphia: Elsevier; 2019.
4. Drake RL, Vogl W, Mitchell AWM. Gray’s Atlas of Anatomy. 2nd ed. Philadelphia: Elsevier; 2021.
5. Warner JJ, Micheli LJ, Arslanian LE. Shoulder Injuries in the Athlete. In: DeLee JC, Drez D Jr, Miller MD, editors. DeLee & Drez’s Orthopaedic Sports Medicine. 4th ed. Philadelphia: Elsevier; 2015. p. 1123-1140.
6. Neer CS 2nd. Impingement Lesions. Clin Orthop Relat Res. 1983;(173):70-77.
7. Paley KJ, Buzas D, Zuckerman JD. Shoulder Pain and Disability: Epidemiology and Diagnosis. J Am Acad Orthop Surg. 2018;26(7):e148-e158.