Correct Answer: B. Complete tear of supraspinatus
Painful arc syndrome (PAS) is a clinical sign of subacromial impingement where pain occurs during active abduction between 60–120° of shoulder abduction. The discriminating fact is that PAS requires an intact, inflamed, or partially torn tendon that can still generate tension and be compressed against the acromion. In a complete tear of supraspinatus, the tendon is fully disrupted and cannot generate sufficient tension to be impinged against the acromion during this arc. Patients with complete tears typically present with loss of active abduction (inability to initiate or maintain abduction) rather than pain in a specific arc. The pain in complete tears is usually present throughout the range or absent during active movement because the tendon cannot be pinched. In contrast, partial tears, tendinitis, bursitis, and fractures of the greater tuberosity all cause subacromial impingement and inflammation, producing the characteristic painful arc. This is a classic orthopedic sign taught in Indian medical schools and is a high-yield concept for NEET PG examinations.
Why the other options are wrong
A. Supraspinatus tendinitis — Supraspinatus tendinitis causes inflammation and swelling of the tendon, leading to subacromial impingement. The inflamed tendon is compressed against the acromion during the 60–120° arc of abduction, producing the classic painful arc. This is a textbook cause of PAS and is frequently tested in NEET PG. C. Subacromial bursitis — Subacromial bursitis causes inflammation of the bursa lying between the rotator cuff and acromion. During abduction in the painful arc range, the inflamed bursa is compressed, producing pain. This is one of the most common causes of PAS in clinical practice and is a standard examination finding. D. Fracture greater tuberosity — Fracture of the greater tuberosity alters the anatomy of the humeral head and reduces the subacromial space. This leads to impingement of the rotator cuff tendons and bursa during abduction, producing the painful arc. Healing callus and inflammation further contribute to impingement.
High-Yield Facts
- Painful arc syndrome occurs between 60–120° of abduction and requires an intact or partially torn tendon that can be impinged.
- Complete rotator cuff tear presents with loss of active abduction (positive drop arm test), NOT painful arc.
- Partial tear, tendinitis, bursitis, and greater tuberosity fracture all cause subacromial impingement and produce PAS.
- In complete tear, the tendon cannot generate tension to be compressed; pain is diffuse or absent during active movement.
- Drop arm test (inability to lower arm from 90° abduction) is the hallmark sign of complete supraspinatus tear, distinguishing it from PAS.
Mnemonics
PAS Causes (INTACT or PARTIAL tendon needed) Inflammation (tendinitis, bursitis) → Partial tear → Anatomy altered (fracture) = PAS. Complete tear = Cannot impinge (tendon disrupted). Complete Tear vs PAS DROP arm test positive = complete tear (loss of active abduction). Painful arc 60–120° = PAS (intact/partial tendon impinged). Opposite findings.
NBE Trap
NBE exploits the common misconception that all rotator cuff pathology causes painful arc. Students who conflate "rotator cuff tear" with "painful arc" will incorrectly select option B, missing the critical distinction that only complete tears eliminate the painful arc by abolishing tendon tension.
Clinical Pearl
In Indian orthopedic practice, a patient presenting with shoulder pain and a positive painful arc during abduction is initially managed conservatively (NSAIDs, physiotherapy) assuming subacromial impingement. However, if the patient also has a positive drop arm test or loss of active abduction, imaging (ultrasound or MRI) is urgently obtained to rule out complete rotator cuff tear, which may require surgical intervention—a critical clinical distinction that changes management.
_Reference: Bailey & Love Ch. 52 (Shoulder); Harrison Ch. 329 (Musculoskeletal Disorders)_