What is the likely diagnosis and first‑line treatment for a healthy 24‑year‑old man with a one‑year history of right‑shoulder pain reproduced by abduction, internal rotation, and overhead activities?

Subacromial Impingement Syndrome / Rotator Cuff Tendinopathy

This 24-year-old male has subacromial impingement syndrome (also termed rotator cuff tendinopathy), and the first-line treatment is a structured physical therapy program focusing on rotator cuff and scapular stabilizer strengthening, combined with relative rest from overhead activities. 1

Diagnosis

The clinical presentation is classic for subacromial impingement syndrome in a young adult:

• Pain reproduced by abduction, internal rotation, and overhead movements is the hallmark of subacromial impingement, reflecting compression of the supraspinatus tendon and subacromial bursa beneath the coracoacromial arch 2, 3
• One-year duration indicates chronic tendinopathy with degenerative changes rather than acute inflammation, as most patients present after prolonged symptoms during which acute inflammation has subsided and been replaced by collagen fiber degeneration 4
• Age 24 years places him in the demographic where secondary impingement (from rotator cuff weakness and ligamentous laxity causing dynamic instability) is more common than primary structural impingement 3

Key Physical Examination Findings to Confirm

• Hawkins' test (forcible internal rotation with arm flexed forward at 90°) has 92% sensitivity for impingement 3
• Neer's test (passive forward flexion) has 88% sensitivity 3
• Focal weakness during abduction with external or internal rotation suggests rotator cuff involvement without complete tear 1
• Pain in the anterior or anterolateral shoulder that worsens with overhead activities is characteristic 3
• Preserved passive range of motion distinguishes this from adhesive capsulitis 1

Imaging Recommendations

• Plain radiographs are mandatory as the initial imaging study (AP in internal rotation, AP in external rotation, and axillary or scapular Y view) to rule out bony pathology, though they typically do not show soft tissue changes of tendinopathy 4, 1
• MRI is NOT required at initial presentation when clinical findings clearly establish the diagnosis 1
• MRI becomes appropriate only if: symptoms persist despite 3-6 months of adequate conservative therapy, there is clinical suspicion for full-thickness rotator cuff tear (marked strength loss), or imaging is needed for surgical planning 1
• Ultrasound (if local expertise available) is equivalent to MRI for rotator cuff evaluation, with 85% sensitivity and 90% specificity 1, 3

First-Line Treatment

Physical therapy is the most appropriate initial intervention, with evidence showing 80% of patients achieve full recovery within 3-6 months. 1

Structured Rehabilitation Protocol

Phase 1: Relative Rest and Pain Control (First 2-4 weeks)

• Complete rest from all aggravating activities (overhead movements, abduction, internal rotation) until asymptomatic 4, 1
• NSAIDs for acute pain management during the initial inflammatory phase 1
• Ice, heat, and soft tissue massage as adjunctive modalities 1
• Avoid overhead pulley exercises, which encourage uncontrolled abduction and can worsen rotator cuff pathology 1

Phase 2: Range of Motion Restoration (Weeks 2-6)

• Aggressive stretching and mobilization focusing especially on external rotation and abduction to prevent frozen shoulder 1
• Improve range of motion through stretching techniques before initiating strengthening 1

Phase 3: Strengthening (Weeks 6-12)

• Rotator cuff strengthening once pain-free motion is achieved, with emphasis on eccentric exercises which are specifically recommended to promote tendinopathy healing 1
• Scapular stabilizer strengthening is critical, as scapular dyskinesis contributes significantly to rotator cuff injury and must be addressed 1, 3
• External rotation exercises are particularly important, as lateral rotation is the factor most significantly related to onset of shoulder pain 1

Phase 4: Return to Activity (Months 3-6)

• Return to activities may be allowed after completing a functional, progressive, and individualized program over 1-3 months without evidence of symptoms 1

Adjunctive Interventions

• Subacromial corticosteroid injection should be considered for more severe cases or if conservative measures fail after 4-6 weeks, targeting the subacromial-subdeltoid bursa (not the glenohumeral joint) 2, 1
• Post-injection management requires relative rest for 48-72 hours, gradual return to activity as pain permits, and continuation of physical therapy 2
• Functional electrical stimulation (FES) to improve shoulder lateral rotation has shown significant treatment effects for pain-free lateral rotation 1

Critical Pitfalls to Avoid

• Do not overlook scapular dyskinesis, as poor scapular coordination is both cause and effect of rotator cuff pathology and must be addressed in treatment 1, 3
• Do not refer to orthopedics prematurely before a well-managed 3-6 month trial of conservative therapy; only about 9% of patients with subacromial impingement ultimately require surgical referral 1
• Do not order MRI at initial presentation when clinical findings are diagnostic; this adds unnecessary cost without changing initial management 1
• Avoid overhead pulley exercises during rehabilitation, as these encourage uncontrolled abduction and worsen rotator cuff pathology 1

When to Escalate Care

• Orthopedic referral becomes appropriate if: symptoms persist despite 3-6 months of adequate conservative therapy, there is clinical suspicion for full-thickness rotator cuff tear (marked weakness, inability to maintain arm elevation), or the patient fails evidence-based conservative management 1
• Surgical decompression affords good relief of pain when conservative management fails 5