National Physical Therapy Examination (NPTE) Practice Exam

During passive shoulder abduction, which muscle's function is being primarily assessed when looking for scapular winging?

1. Upper trapezius

2. Lower trapezius

3. Serratus anterior

4. Latissimus dorsi

The correct answer is: Serratus anterior

The assessment of scapular winging during passive shoulder abduction primarily evaluates the function of the serratus anterior muscle. This muscle is crucial for the stabilization and proper movement of the scapula against the thoracic wall. When the arm is elevated, the serratus anterior facilitates upward rotation and protraction of the scapula. If the serratus anterior is weak or not functioning correctly, the scapula may wing away from the thoracic wall, which is observable during passive shoulder movements. The action of the serratus anterior is particularly important in maintaining the position of the scapula during arm elevation, as it works in tandem with other muscles to ensure smooth and efficient movement. Therefore, the presence of scapular winging can be indicative of weakness or dysfunction in the serratus anterior. The other muscles listed have their own roles in shoulder and scapular movement but do not primarily influence scapular winging in the same manner as the serratus anterior. Understanding the roles of different muscles helps differentiate the implications of scapular mechanics during upper extremity motion.