**Core Concept:** Understanding the muscles that contribute to shoulder joint movement and their absence/inactivity.

**Why the Correct Answer is Right:** The correct answer, **D:** Pectoralis Major, is a large muscle that originates from the clavicle and ribs, and inserts on the humerus. It primarily functions in adduction and internal rotation of the humerus at the shoulder joint. When Pectoralis Major is inactive or paralyzed, it prevents the humerus from being pulled medially and rotated inward, thereby having no effect on the shoulder joint.

**Why Each Wrong Option is Incorrect:**

A. **Biceps Brachii (Option A):** Although it contributes to flexion and rotation of the humerus, its action at the shoulder joint is not completely absent.

B. **Triceps Brachii (Option B):** Similarly, this muscle contributes to extension and external rotation of the humerus, making it not entirely irrelevant to shoulder joint movement.

C. **Subscapularis (Option C):** Though Subscapularis is responsible for internal rotation of the humerus, it is not completely inactive when the arm is placed in abduction, allowing some effect on the shoulder joint.

**Clinical Pearl:** Understanding muscle anatomy and their actions is crucial for clinical decision-making, particularly in cases of muscle injuries or paralysis. Knowledge of these muscles' functions enables accurate diagnosis, treatment planning, and prognosis estimation.

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**Why the Correct Answer is Right:** Absence of Pectoralis Major results in minimal to no adduction and internal rotation at the shoulder joint, thus preventing significant alteration in joint position.

**Why Each Wrong Option is Incorrect:**

A. **Biceps Brachii (Option A):** Although it is partially inactive when the arm is abducted, its contribution to flexion and rotation of the humerus makes it more likely to influence shoulder joint movement.

B. **Triceps Brachii (Option B):** Although Triceps Brachii is less active during abduction, its contribution to extension and external rotation of the humerus indicates a potential impact on the shoulder joint.

C. **Subscapularis (Option C):** Although Subscapularis is less active in abducted arm, its internal rotation function still indicates an influence on shoulder joint movement.

**Clinical Pearl:** A complete understanding of muscle functions is essential for accurate assessment of shoulder joint dysfunction and formulating appropriate treatment plans. In cases of suspected Pectoralis Major injury or paralysis, assessing the effect of other shoulder stabilizers becomes crucial for appropriate management strategies.