Which tendon contributes to the stability of the shoulder and assists with arm rotation?

The subscapularis plays a crucial role in shoulder stability and arm rotation. As one of the four rotator cuff muscles, it is situated on the anterior surface of the scapula and helps to stabilize the glenohumeral joint during movement. Specifically, it is involved in internal rotation of the arm, allowing for various activities that require arm positioning and stability.

In addition to providing stability, the subscapularis engages during lifting and reaching motions, making it essential for both dynamic movement and maintaining shoulder integrity. This tendon’s unique alignment and muscular structure allow it to resist dislocation and support the arm's range of motion, particularly during overhead activities.

Understanding the other tendons’ roles, the supraspinatus primarily aids in arm abduction, the biceps tendon contributes to elbow flexion and shoulder stabilization but is not primarily involved in shoulder rotation, and the triceps tendon mainly facilitates elbow extension. This context highlights why the subscapularis is the most relevant tendon for shoulder stability and arm rotation among the listed options.