Which muscle is responsible for shoulder abduction and stabilizing the shoulder joint?

The deltoid muscle is primarily responsible for shoulder abduction, which is the movement of the arm away from the body. This muscle covers the shoulder joint and plays a significant role in various shoulder movements, particularly during the first 15 degrees of abduction.

In addition to facilitating shoulder abduction, the deltoid also helps stabilize the shoulder joint. It provides a protective and supportive function for the glenohumeral joint, ensuring stability during both dynamic movements and while maintaining posture.

While the supraspinatus initiates the early phase of shoulder abduction, the deltoid takes over after this initial movement. Other muscles listed, like the infraspinatus and subscapularis, primarily assist with shoulder rotation and internal stability but do not perform the main action of abduction to the extent that the deltoid does. The role of the deltoid in both movement and stabilization makes it the key muscle in this context.