The shoulder is one of the largest and most complex joints in the body. The shoulder joint is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade), like a ball and socket. Other important bones in the shoulder include:
The acromion is a bony projection off the scapula.
The clavicle (collarbone) meets the acromion in the acromioclavicular joint.
The coracoid process is a hook-like bony projection from the scapula.