Most Likely Diagnosis: Adhesive Capsulitis (Frozen Shoulder)
The clinical presentation of an 8-week history of scapular-region shoulder pain with marked limitation in passive range of motion—specifically the inability to reach behind the back—in a 30-year-old woman most strongly suggests adhesive capsulitis (frozen shoulder). 1
Key Diagnostic Features Supporting Adhesive Capsulitis
The inability to reach behind her back is the critical diagnostic clue here. This represents restricted passive range of motion, which is the hallmark distinguishing feature of adhesive capsulitis from rotator cuff pathology 1.
Why This Is Adhesive Capsulitis Rather Than Rotator Cuff Tear:
Passive ROM restriction: Adhesive capsulitis presents with diffuse shoulder pain and restricted passive range of motion on examination 2. The patient cannot reach behind her back "at all"—this suggests capsular restriction, not just weakness.
Age consideration: While rotator cuff tears are more common in patients over 40 years and typically result from degenerative changes 3, this 30-year-old patient fits the demographic for adhesive capsulitis, which affects 2-5% of individuals with higher rates in women 1.
Clinical phase: At 8 weeks, she is likely in the "freezing" phase of adhesive capsulitis, characterized by progressive pain and motion loss 1.
Distinguishing From Rotator Cuff Pathology:
If this were a rotator cuff tear, you would expect:
- Preserved passive ROM with limited active ROM due to weakness 4
- Positive empty can test, external rotation weakness, and impingement signs 2
- Pain specifically with overhead activities rather than global restriction 3
The fact that she has difficulty lifting her baby suggests functional limitation, but the complete inability to reach behind her back indicates capsular contracture, not isolated rotator cuff weakness.
Clinical Pitfalls to Avoid:
Do not assume all shoulder pain in young adults with lifting difficulty is rotator cuff disease. While rotator cuff tears in young adults typically result from traumatic injury 3, the absence of trauma history and the presence of passive motion restriction point away from this diagnosis.
The scapular location of pain can be misleading—shoulder pathology commonly refers pain to the scapular region due to convergence of afferent signals 4, so focus on the motion restriction pattern rather than pain location alone.
Confirmatory Examination Findings to Expect:
- Global restriction of passive ROM in all planes (abduction, forward elevation, internal and external rotation)
- Pain at end-range of motion
- No specific weakness on rotator cuff strength testing (unlike rotator cuff tears)
- Negative impingement signs (unlike rotator cuff tendinopathy)
Imaging Considerations:
Plain radiographs will likely be unremarkable 1. If imaging is pursued, MRI may reveal thickened capsule, synovial hypertrophy, and joint capsule edema 1, though diagnosis is primarily clinical based on the characteristic passive motion restriction pattern.