Scapulohumeral Rhythm

Scapulohumeral rhythm is an important concept to understand when assessing the shoulder. This rhythm is based on the movement ratio between the humerus and scapula, more specifically the scapulothoracic joint and the glenohumeral joint. The ratio is for every 3° of movement at the shoulder, 1° is at the scapulothoracic joint and 2° are at the glenohumeral joint. The clinical relevance of this is when you are measuring shoulder elevation and if something seems abnormal you have to take into consideration the relationship of the two joints and their components. Full ROM occurs when the scapula and humerus move synchronously, during which the humeral head must laterally rotate. ROM measurements can be affected when there is rotator cuff muscle weakness which results in the humeral head elevating in the glenoid fossa causing an impingement. Understanding scapulohumeral rhythm will help you better assess and address your client's needs.