Most common injured MUSCLE in rotator cuff is :
**Core Concept**
The rotator cuff is a group of muscles and tendons surrounding the shoulder joint, providing stability and facilitating movement. The muscles involved are supraspinatus, infraspinatus, teres minor, and subscapularis. Injury to these muscles can lead to shoulder pain and dysfunction.
**Why the Correct Answer is Right**
The supraspinatus muscle is the most commonly injured muscle in the rotator cuff. This is because it is the most superficial and exposed to mechanical stress, particularly during overhead activities and repetitive shoulder movements. The supraspinatus tendon is also more prone to degeneration due to its relatively poor blood supply, making it more susceptible to injury and wear and tear.
**Why Each Wrong Option is Incorrect**
**Option A:** Infraspinatus - While the infraspinatus muscle can be injured, it is less commonly affected than the supraspinatus due to its deeper location and more robust blood supply.
**Option B:** Teres minor - Teres minor injuries are relatively rare and usually occur in conjunction with other rotator cuff injuries.
**Option C:** Subscapularis - Subscapularis injuries are less common than supraspinatus injuries and often occur in the context of a more complex shoulder pathology.
**Clinical Pearl / High-Yield Fact**
In clinical practice, a positive "empty can" test (also known as the "supraspinatus test") can help diagnose supraspinatus tendonitis or rupture. This test involves the examiner holding the patient's arm in 90 degrees of abduction and internal rotation, then applying downward pressure to the arm while the patient attempts to resist. A positive test is indicated by weakness or pain in the supraspinatus muscle.
**Correct Answer: A. Supraspinatus**