**Question:** Abduction of shoulder is done by all, EXCEPT

A. deltoid muscle
B. supraspinatus muscle
C. subscapularis muscle
D. infraspinatus muscle

**Core Concept:** The primary function of the shoulder joint is to provide a wide range of motion, which is achieved through the coordinated action of various muscles. The muscles that primarily contribute to abduction are the deltoid, supraspinatus, infraspinatus, and subscapularis muscles.

**Why the Correct Answer is Right:** The correct answer, **Option B - Sugraspinatus muscle**, is wrong because it is primarily involved in rotation and internal rotation of the shoulder joint rather than abduction.

**Why Each Wrong Option is Incorrect:**

**Option A - Deltoid muscle:** The deltoid muscle is the primary mover of the shoulder girdle and plays a crucial role in abduction. The deltoid muscle consists of three parts: anterior, middle, and posterior, each contributing to different shoulder movements, including abduction.

**Option C - Subscapularis muscle:** The subscapularis muscle is involved in internal rotation, not abduction. It is a part of the rotator cuff muscles and acts as a stabilizer of the glenohumeral joint.

**Option D - Infraspinatus muscle:** Similar to the subscapularis muscle, the infraspinatus muscle is involved in internal rotation and not abduction. It is a part of the rotator cuff muscles and helps to stabilize the glenohumeral joint.

**Option A - Deltoid muscle:** The deltoid muscle is crucial in abduction, as it consists of three parts (anterior, middle, and posterior) that contribute to various shoulder movements, including abduction.

**Correct Answer:** The correct answer is **Option C - Subscapularis muscle**. The subscapularis muscle is involved in internal rotation of the shoulder joint and not abduction. It plays a vital role in stabilizing the glenohumeral joint and is a part of the rotator cuff muscles.

**Clinical Pearl:** Understanding the anatomy and function of the shoulder muscles is essential for accurate diagnosis and treatment of shoulder disorders. A thorough clinical examination should involve assessing the strength, range of motion, and stability of the shoulder muscles, particularly the rotator cuff muscles like the subscapularis, supraspinatus, infraspinatus, and teres minor. This helps in identifying muscle weakness or imbalance, which may contribute to shoulder pain, instability, or limited range of motion.