The Shoulder


The shoulder is one of the most complex joints with the greatest range of motion of any joint in the human body. It straddles a razors thin edge between stability and instability - which is what allows it to have such an incredible range of motion. Four structures contribute to this function - bone, cartilage, tendon, and ligaments. The bony architecture of the shoulder is that of a ball and socket joint. The socket (glenoid) is rather flat and has a larger radius than the ball (humeral head). Both are lined by a thin layer of articular cartilage that help the shoulder move freely without friction. Shoulder stability is provided by the labrum which is like a rubber "O" ring that goes around the socket and deepens and provides a physical restraint similar to a speed bump. The motion of the shoulder is powered by several muscles the largest and most powerful is the deltoid. Aiding the deltoid to its heavy lifting is a group of four muscles whose tendons join together in a cuff to form the rotator cuff. An injury to any one of these systems can lead to shoulder pain and dysfunction. Learn more about the conditions that Dr. Seneviratne treats in the following sections.