A 42-year-old female physiotherapist from Mumbai reports chronic left shoulder pain for 8 months with difficulty reaching behind her back to fasten her bra. She has no history of trauma. On examination, the "lift-off test" (Gerber's test) is positive, and she cannot internally rotate the shoulder against resistance. Passive internal rotation is full. What is the most likely rotator cuff muscle involved?

Explanation

## Subscapularis Tear: Clinical Diagnosis via Lift-Off Test ### The Lift-Off Test (Gerber's Test) **Key Point:** The lift-off test is the gold standard for assessing subscapularis function. The patient places the dorsum of the hand on the lumbar spine and attempts to lift it away from the body (internal rotation against gravity). ### Anatomical Basis of the Lift-Off Test **High-Yield:** The subscapularis is the only muscle capable of internally rotating the shoulder when the arm is behind the back. This position (hand on lumbar spine) isolates subscapularis function: - The arm is adducted and internally rotated - The pectoralis major cannot assist effectively - The latissimus dorsi is stretched - Only the subscapularis can lift the hand away from the spine ### Subscapularis Anatomy and Function | Feature | Detail | |---------|--------| | **Origin** | Subscapular fossa (anterior scapula) | | **Insertion** | Lesser tubercle of humerus | | **Innervation** | Upper and lower subscapular nerves (C5–C6) from posterior cord | | **Primary action** | Internal rotation (especially with arm adducted) | | **Secondary action** | Adduction and anterior shoulder stability | | **Clinical test** | Lift-off test (Gerber's test) | ### Why Passive Internal Rotation Is Preserved **Clinical Pearl:** Preservation of passive internal rotation in the presence of a positive lift-off test confirms a rotator cuff tear (not capsular restriction). The joint capsule and ligaments are intact, allowing passive motion. The deficit is purely muscular (loss of active force generation). ### Differential Diagnosis: Rotator Cuff Tears by Clinical Sign | Muscle | Primary Test | Positive Finding | Loss of Function | |--------|---|---|---| | **Supraspinatus** | Drop arm sign | Cannot lower arm from 90° abduction | Abduction 0–15° | | **Infraspinatus** | External rotation lag sign | Lag in external rotation | External rotation | | **Teres minor** | External rotation lag sign | Lag in external rotation | External rotation | | **Subscapularis** | Lift-off test (Gerber's) | Cannot lift hand from lumbar spine | Internal rotation (arm adducted) | ### Why This Patient's History Fits Subscapularis Tear 1. **Difficulty fastening bra** = inability to reach behind back and internally rotate 2. **Positive lift-off test** = subscapularis dysfunction confirmed 3. **No trauma** = consistent with chronic degenerative tear (common in middle-aged individuals) 4. **Preserved passive ROM** = confirms rotator cuff tear, not capsular pathology ### Subscapularis Tear: Epidemiology and Pathophysiology **Mnemonic:** **SITS** muscles, but subscapularis is the **anterior** rotator cuff (the other three are posterior). Subscapularis tears are less common than supraspinatus tears but are associated with: - Chronic overhead activities (her profession as a physiotherapist) - Anterior shoulder instability - Internal impingement - Degenerative changes ### Alternative Tests for Subscapularis - **Belly-press test** (Barth's test): Patient pushes palm against abdomen; positive if elbow flexes (loss of internal rotation strength) - **Bear-hug test**: Patient hugs chest; inability to maintain position suggests subscapularis weakness - **Lift-off test** is most specific and sensitive ### Why Not Supraspinatus? Supraspinatus tears present with **drop arm sign** (inability to lower arm from 90° abduction), not lift-off test positivity. Supraspinatus is responsible for abduction initiation, not internal rotation.