Which structure is primarily responsible for the movement involved in shoulder impingement?

The structure primarily responsible for the movement involved in shoulder impingement is the humerus. In the context of shoulder mechanics, the humerus is the upper arm bone that connects with the shoulder joint. During various arm movements, particularly overhead actions, the alignment and positioning of the humerus can significantly impact the space available within the shoulder joint, specifically the subacromial space where impingement occurs.

When the humerus is elevated or rotated incorrectly, it can cause it to collide with the acromion process of the scapula, leading to irritation of the tendons and bursae in that area. This impingement can result in pain and restricted movement, necessitating an understanding of proper shoulder mechanics and movement patterns.

The other structures, such as the scapula, clavicle, and ribs, play supporting roles in shoulder movement and stability, but it is the humerus that directly engages in the movement patterns that often lead to impingement issues. A proper evaluation of shoulder dysfunction often focuses on the function of the humerus and its relationship with the surrounding structures.