Which muscle causes scapular winging?

• A. Serratus Anterior
• B. Trapezius
• C. Rhomboids
• D. Pectoralis Minor

Answer: (A)

Winging of the scapula happens when the muscle that keeps the medial border pressed against the rib cage is weak or paralyzed. Serratus anterior does that job, attaching along the medial border of the scapula and wrapping around the chest to anchor the scapula to the thoracic wall and to upwardly rotate the scapula during arm elevation. When serratus anterior is weak (often from injury to the long thoracic nerve), the medial edge of the scapula lifts off the rib cage, causing the classic winging appearance. The other muscles mainly support different scapular motions—trapezius stabilizes and moves the shoulder blade in other patterns, rhomboids retract and elevate, and pectoralis minor tilts the scapula forward and down—so they don’t produce the same winging pattern as serratus anterior.