Which bone is involved in forming the shoulder joint?

The shoulder region involves three bones that work together. The humerus is the upper arm bone whose rounded head fits into the shallow glenoid cavity of the scapula (shoulder blade), forming the glenohumeral joint - the main ball-and-socket joint of the shoulder. The clavicle (collarbone) connects to the scapula at the acromioclavicular joint and to the sternum at the sternoclavicular joint, providing anterior structural support to the entire shoulder complex.

Because the shoulder joint complex is formed by the articulation of all three bones - the humerus, scapula, and clavicle - each plays a role in the overall structure and function of the shoulder. The humerus provides the mobile arm element, the scapula provides the socket and muscular attachment platform, and the clavicle acts as a strut that holds the shoulder out from the trunk and transmits forces from the upper limb to the axial skeleton.

The correct answer is therefore that all of these bones are involved in forming the shoulder joint.