Description

• Shoulder pain commonly affects patients of all ages.
• Causes include acute trauma, overuse during sports, infection, and activities of everyday living.
• Age plays an important role in determining the etiology of shoulder pain.
• Onset and characteristics of pain, mechanism of injury, and limitation narrow the differential diagnosis.

Epidemiology

• Shoulder pain accounts for 16% of all musculoskeletal (MSK) complaints.
• The lifetime prevalence of shoulder pain is ~70%.
• Predominant etiology varies with age:
  • <30 years: shoulder instability
  • 30 to 60 years: rotator cuff (RTC) disorder, impingement syndrome, partial tears
  • >60 years: full-thickness tear, glenohumeral OA

Incidence
The incidence of shoulder pain is 7 to 25 cases per 1,000 patients, with a peak incidence in the 4th to 6th decades.

Etiology and Pathophysiology

Pathology varies with cause:

• Trauma—fracture, dislocation, ligament/tendon tear, acromioclavicular (AC) separation
• Overuse—RTC pathology, biceps tenosynovitis, bursitis, muscle strain, apophyseal injuries
• RTC disorders most commonly result from repetitive overhead activity, leading to RTC impingement with a three-stage progression:
  • Stage I: tendinopathy
  • Stage II: partial RTC tear
  • Stage III: full-thickness RTC tear
• Subacromial bursitis can occur with RTC disorders but is rarely an isolated diagnosis.
• Age related: In pediatric athletes, instability and physeal injuries are more common. With increasing age, the incidence of AC and glenohumeral joint OA, adhesive capsulitis, and RTC tear rises.
• Rheumatologic: rheumatoid arthritis, polymyalgia rheumatica, fibromyalgia
• Infectious: septic arthritis
• Referred pain: neck, gallbladder, diaphragm

Risk Factors

• Repetitive overhead activity
• Overhead and upper extremity weight-bearing sports (baseball, softball, swimming, tennis, volleyball)
• Weight lifting: AC joint disorders
• Rapid increases in training frequency or load (often associated with improper technique)
• Muscle weakness or imbalance
• Trauma or fall onto the shoulder
• Diabetes, thyroid disorders and other autoimmune diseases, female gender, and age 40 to 60 years are risk factors for adhesive capsulitis.

General Prevention

• Maintain strength and range of motion (ROM).
• Avoid repetitive overhead activities (pitch counts).
• Proper technique (pitching, weight lifting)