What is the likely diagnosis and management for a 29-year-old active duty female with acute onset of right shoulder pain following a dumbbell shoulder press, presenting with 1-2/10 pain at rest, increasing pain with abduction or forward flexion, tenderness to palpation (TTP) over the acromion and glenohumeral head, and 4/5 strength compared to the left arm?

Acute Subacromial Impingement Syndrome with Likely Rotator Cuff Tendinopathy

This presentation is most consistent with acute subacromial impingement syndrome with rotator cuff tendinopathy (likely supraspinatus involvement), and initial management should include rest from aggravating activities, NSAIDs or acetaminophen, and early physical therapy focusing on rotator cuff strengthening and scapular stabilization. 1, 2

Clinical Diagnosis

The mechanism of injury (eccentric loading during the lowering phase of shoulder press), acute onset of "pinching" pain, pain with abduction and forward flexion, tenderness over the acromion/glenohumeral region, and 4/5 strength all point to acute rotator cuff injury within the spectrum of subacromial impingement. 1, 2

Key Diagnostic Features Present:

• Painful arc syndrome: Pain increasing with abduction/forward flexion is the hallmark clinical sign of impingement, typically manifesting between 70-120 degrees of abduction 3
• Acute mechanism: The eccentric loading phase (lowering weight) during shoulder press creates maximum tension on the rotator cuff tendons, particularly the supraspinatus 2
• Weakness without neurological deficit: 4/5 strength with intact reflexes suggests pain-related inhibition or partial tendon injury rather than nerve pathology 1

Immediate Management Algorithm

First-Line Conservative Treatment (Start Immediately):

• Activity modification: Avoid overhead activities and movements that reproduce the pain for 7-14 days 1, 2
• Pharmacologic management: NSAIDs (ibuprofen 400-600mg TID or naproxen 500mg BID) for 7-14 days, or acetaminophen 650-1000mg every 6 hours if NSAIDs contraindicated 4, 1
• Ice application: 15-20 minutes every 2-3 hours for the first 48-72 hours 1

Imaging Decision Point:

Standard shoulder radiographs (AP in internal/external rotation plus axillary or scapular-Y view) are mandatory as the first imaging step to exclude fracture, dislocation, or significant bony pathology before attributing symptoms purely to soft tissue injury. 5, 6, 4

• Radiographs should be obtained upright, as shoulder malalignment can be underrepresented on supine imaging 6
• In this 29-year-old active duty patient with acute traumatic mechanism, radiographs will rule out occult fractures (including greater tuberosity avulsion) and acromioclavicular joint pathology 5

Advanced Imaging Indications:

If radiographs are normal and symptoms persist beyond 4-6 weeks of conservative management, or if there is clinical suspicion for rotator cuff tear (significant weakness, inability to maintain arm elevation), proceed with MRI without contrast or ultrasound. 5, 6

• MRI without contrast is preferred in the acute setting because post-traumatic joint effusion provides natural contrast for assessing intra-articular structures 5
• Ultrasound is an excellent alternative if local expertise is available, particularly for rotator cuff and biceps tendon pathology 6, 4
• MR arthrography is NOT indicated acutely, as it is reserved for chronic or recurrent instability/labral pathology in patients under 35 years 5, 6

Physical Therapy Protocol (Initiate Within 1-2 Weeks):

Early physical therapy is critical and should focus on:

• Avoid overhead pulleys, which encourage uncontrolled abduction and may worsen impingement 4
• Range of motion exercises through controlled stretching focusing on external rotation and abduction 4
• Rotator cuff strengthening once acute pain subsides, emphasizing supraspinatus, infraspinatus, and scapular stabilizers 1, 2
• Scapular stabilization exercises to address biomechanical dysfunction that contributes to impingement pathophysiology 2, 7

Red Flags Requiring Urgent Specialist Referral:

• Progressive weakness despite conservative management (suggests complete rotator cuff tear) 4, 2
• Inability to actively elevate arm (suggests massive rotator cuff tear requiring expedited repair) 4
• Neurological deficits developing in the upper extremity 4
• Radiographic evidence of displaced fracture (particularly greater tuberosity) 4, 3

Expected Timeline and Follow-Up:

• Re-evaluate at 2 weeks: If no improvement with conservative measures, consider corticosteroid injection into subacromial space 1, 2
• Re-evaluate at 4-6 weeks: If persistent symptoms despite physical therapy and NSAIDs, obtain MRI or ultrasound to assess for rotator cuff tear 2
• Most patients respond to conservative treatment within 6-12 weeks 1, 2

Critical Pitfalls to Avoid:

• Do not delay radiographs: Even in young patients with "obvious" soft tissue injury, fractures (especially greater tuberosity avulsions) can occur and alter management 5
• Do not rush to advanced imaging: In the absence of red flags, MRI in the first 2-4 weeks is premature and unlikely to change initial conservative management 2
• Do not assume "impingement syndrome" is a specific diagnosis: This term encompasses a spectrum of pathology including tendinopathy, partial tears, bursitis, and biomechanical dysfunction—treatment should address the specific movement impairments identified 7
• Do not prescribe prolonged rest: Early controlled mobilization and strengthening prevent stiffness and chronic dysfunction 1, 2