What Is the Biomechanics of the Shoulder?

The shoulder is an intricate multidimensional joint complex consisting of four separate connection points of bones responsible for the movement of the hand, arm and shoulder. The biomechanics of the shoulder is how the shoulder moves, as well as the scientific study of this movement. This can include intentional movements as well as movements in response to internal and external changes or forces acting upon the shoulder.

The shoulder is made up of separate joints that link the arm to the torso, and includes bones in the trunk, including the shoulder blade and the collar bone — these are known as the scapula and clavicle, respectively. These structures are attatched to the humerus, which is the body's upper arm bone. Due to its complex nature, the shoulder is one of the most mobile joints in the body. This multi-faceted system gives the shoulder the ability to move in straight and rotational planes. Understanding the biomechanics of the shoulder makes it possible to prevent or treat injuries limiting the mobility of the shoulder area.

Having a basic knowledge of the structure of the shoulder is important to understanding the biomechanics of the shoulder. For example, the glenohumeral joint is the area where the upper arm bone connects to the shoulder blade by resting in a hollowed out area called the glenoid fossa. This type of joint is referred to as a ball-and-socket. This joint allows the shoulder to move in straight planes, forward or backward, and side to side. This kind of connection also lets the shoulder rotate so the arm can swing in a circular pattern without hitting against the sides of the bony connection point. The circular or rotational components of shoulder movement are dependent on the ability of the shoulder blade to move unrestricted.

The acromioclavicular joint is another important bony connection that gives the arm the ability to rotate. It also allows for protraction and retraction, or the movement of the arm in a forward and backward manner. Movement of the shoulder blade and the collar bone to position the glenoid fossa in the correct position for appropriate movement is necessary for smooth motion of the arm. Understanding these biomechanics of the shoulder allows for better insight into shoulder problems resulting in movement restrictions. In other words, if the arm has lost the ability to move out away from the body and up towards the head, the movement of the shoulder blade as well as the collar bone must be evaluated in order to restore pain-free, unrestricted movement of the shoulder.