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Rotator Cuff Impingement Syndrome

BASICS

  • Definition: Compression of rotator cuff tendons and subacromial bursa between the humeral head and the coracoacromial arch/proximal humerus.
  • Most common cause of atraumatic shoulder pain in adults >25 years.
  • Painful arc: Pain is maximal with arm abduction between 60–120°.
  • Stages:
  • Stage I: Acute inflammation, edema, hemorrhage (age <25y, overuse)
  • Stage II: Tendinosis, partial tear, fibrosis (age 25–40y)
  • Stage III: Full-thickness tear (age >40y)

EPIDEMIOLOGY

  • Shoulder pain: 1% of all primary care visits.
  • Peak incidence: 25/1,000 per year, age 42–46.
  • Impingement: 18–74% of shoulder pain diagnoses.
  • Prevalence: 7–30% in the general population.

RISK FACTORS

  • Repetitive overhead activity (throwing, swimming)
  • Glenohumeral instability or muscle imbalance
  • AC joint arthritis/osteophytes
  • Thickened coracoacromial ligament
  • Shoulder trauma
  • Age, smoking

PREVENTION

  • Proper throwing/lifting technique
  • Rotator cuff and scapular stabilizer muscle strengthening

DIAGNOSIS

History

  • Gradual onset shoulder pain with overhead activity
  • Night pain common, worse when lying on affected side or arm overhead
  • Anterolateral shoulder pain
  • Weakness, ↓ ROM if chronic

Physical Exam

  • Observe for atrophy/asymmetry
  • Neer Impingement Test: Pain with passive shoulder flexion (sensitivity 78%, specificity 58%)
  • Hawkins-Kennedy Test: Pain with internal rotation at 90° flexion (sensitivity 74%, specificity 57%)
  • Empty Can Test: Pain/weakness with resisted abduction in scapular plane (sensitivity 69%, specificity 62%)
  • Lift-off Test: Weakness (subscapularis, specificity 97%)
  • Drop-arm Test: Inability to control descent (rotator cuff tear, specificity 92%)
  • Resisted External Rotation: Weakness = infraspinatus/teres minor
  • Apprehension-Relocation Test: Anterior instability
  • Cervical spine and neurovascular exam to rule out alternative causes

Differential Diagnosis

  • Labral tear
  • AC arthritis
  • Adhesive capsulitis
  • Biceps tendinopathy
  • Calcific tendonitis
  • Glenohumeral arthritis
  • Suprascapular nerve entrapment
  • Cervical radiculopathy

Diagnostic Tests

  • Plain X-rays (AP, axillary, scapular Y):
  • OA, superior humeral head migration, calcific tendonitis, cystic change
  • MRI: Rotator cuff tendinopathy/tear (definitive)
  • US: Sensitive/specific for cuff tears, operator-dependent
  • MR arthrogram: Labral pathology
  • CT: Bony pathology
  • Lidocaine injection test: Relieves pain = impingement syndrome likely; no improvement = consider adhesive capsulitis

TREATMENT

General Measures

  • Initial rest, supervised PT 6–8 weeks
  • Ice/heat for symptom relief
  • Activity modification (avoid overhead use)
  • ROM exercises, progressive strengthening

Medication

  • First line: NSAIDs/analgesics (6–12 weeks)

Additional Therapies

  • Physical therapy: Essential for both conservative and post-surgical management
  • Initial focus: ROM → Strengthening after pain improves
  • Steroid injection: Short-term pain relief, not long-term benefit
  • Surgery: Reserved for refractory cases/complete tears; no proven superiority over conservative therapy
  • Emerging: Platelet-rich plasma (PRP), extracorporeal shock wave therapy (under study)
  • Acupuncture: Possible benefit as adjunct

Referral

  • Failure of conservative management, persistent pain/weakness, full-thickness tear

PATIENT EDUCATION

  • Importance of PT and adherence to rehab
  • Aggressive rehab before considering advanced testing or surgery
  • Symptoms may recur if not fully addressed

PROGNOSIS

  • Most improve with conservative treatment
  • Recovery may be slow; severe/prolonged symptoms reduce response to nonoperative therapy

COMPLICATIONS

  • Progression to tendon retraction (if complete tear)
  • Chronic pain/weakness

ICD-10 CODES

  • M75.40: Impingement syndrome, unspecified shoulder
  • M75.110: Incomplete rotator-cuff tear/rupture, not trauma
  • M75.120: Complete rotator-cuff tear/rupture, not trauma

CLINICAL PEARLS

  • Suspect in middle-aged adults with atraumatic shoulder pain, especially overhead athletes.
  • Supraspinatus most commonly involved.
  • Neer/Hawkins: impingement; Empty can: supraspinatus; Drop-arm: full-thickness tear.
  • Most improve with PT over 6–12 weeks.