College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which muscle is most commonly affected in a Rotator Cuff Tear?

1. Infraspinatus

2. Supraspinatus

3. Teres Minor

4. Subscapularis

The correct answer is: Supraspinatus

The supraspinatus muscle is the most commonly affected muscle in a rotator cuff tear. This muscle is situated at the top of the shoulder and is responsible for initiating the abduction of the arm, which is lifting the arm away from the body. Given its position and function, it is frequently subject to injury, particularly in activities that involve repetitive overhead movements. In many cases, such as in athletes or individuals engaged in manual labor, the supraspinatus can become impinged against the acromion process of the scapula. Over time, this repetitive irritation can lead to inflammation, degeneration, and ultimately a tear. The supraspinatus is often the first muscle involved in rotator cuff pathologies, making it the most commonly injured. While the other muscles of the rotator cuff — the infraspinatus, teres minor, and subscapularis — can also suffer tears, they are less frequently affected in comparison to the supraspinatus. Understanding this distinction is important for diagnosis and treatment strategies in rotator cuff injuries.