National Physical Therapy Examination (NPTE) Practice Exam

Which muscle is heavily involved in humeral stabilization and may limit overhead activities when weakened?

1. Supraspinatus

2. Subscapularis

3. Infraspinatus

4. Teres Major

The correct answer is: Subscapularis

The subscapularis muscle plays a crucial role in stabilizing the humerus within the glenohumeral joint. It is part of the rotator cuff group and provides internal rotation and adduction of the arm, which is essential for various shoulder movements. When the subscapularis is weakened, it can lead to a lack of stability in the shoulder joint, particularly during overhead activities such as lifting or throwing. The instability can result in compensatory movement patterns, pain, or increased risk of injury. In contrast, while the supraspinatus is also involved in shoulder stabilization and is critical for initiating abduction, its primary role is not directly related to humeral stabilization compared to the subscapularis. The infraspinatus also contributes to shoulder stability through external rotation, but its impact is more on rotational control than direct stabilization. The teres major, although it assists in shoulder movement, is not primarily involved in stabilizing the humerus or limiting overhead activity. Therefore, the subscapularis stands out as the muscle most closely associated with humeral stabilization and the potential limitations experienced when it is weakened.