Biomechanics of the upper extremity: arm abduction

This video reviews such a complex movement as arm abduction. Abduction of the arm happens in the frontal plane and can be described as the arm’s movement away from the body’s midline. So, abduction at the shoulder joint causes the free upper limb to move away from the body. It begins with the upper limb positioned parallel to the body and the hand being in an inferior position, continues with the movement of the upper limb to a position perpendicular to the body and ends with the upper limb raised above the shoulder and pointing upward.
This movement involves multiple joints and is closely related to the scapulohumeral rhythm, which can be described as a coordinated interaction between the scapula, clavicle, and humerus to achieve full abduction. It’s important to understand that the first 30 degrees of arm abduction constitute the setting phase, meaning that the movement is mainly glenohumeral, and the scapula remains stationary.
Also, the clavicle demonstrates minimal or no movement. Only after the initial 30 degrees the scapula starts to move, and the glenohumeral and scapulothoracic joints begin to move simultaneously.