shoulder blade

The shoulder blade is a large bone that you can easily feel at the back side of your body. In the photo below you can clearly see the shape of the shoulder blade throught the skin.

The shoulder is the most complex joint in the human body. If you compare the movement freedom of the shoulder to other joints, the only joints that come close are the pelvic joints.

This complexity is also illustrated by difficulty to create effective shoulder prosthesis. Because of the complexity of the design, a shoulder prosthesis is technically years behind other prosthesis.

The Scapulothoracic joint

One of te possible complex movements of the shoulder is the sliding of the shoulder blades over the ribs. When you move your arms backwards, the shoulder blades move towards each other on the back. When stretching the arms forward, the shoulder blades slide to the sides of the ribcage. This combination of ribcage and shoulder blades is often called the Scapulothoracic joint, although it is not technically a real joint.