The shoulder is one of the largest and most complex joints in the body, where many muscles act to provide the widest range of motion of any part of the body. This flexibility is also what makes the shoulder prone to instability and injury.

The shoulder joint is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade), like a ball and socket. The clavicle (collarbone) extends across the front of the shoulder from the sternum to the scapula and helps stabilize the shoulder’s movements.