Scapulohumeral Rhythm

Scapulohumeral rhythm is based on the ratio of movement between the scapula and humerus. For full ROM (range of motion), the humeral head must rotate laterally. It is important for the therapist to pay close attention to this movement. The glenoid fossa needs to maintain a good position in order to move correctly on the head of the humerus. By moving the scapula with one hand and the humerus with the other, the therapist is able to check and see if both are moving simultaneously. If not, this could be caused by impingement, where the scapula would not be able to participate in upward rotation. If the scapula doesn't move at all, that could also be another sign of impingement. Both cause pain for the client.
 Joint congruency results in decreased shear forces of both the glenohumeral joint and scapulothoracic joint. The ratio of both are 1:2 - where every 3° of shoulder movement, there is 1° of scapuloothoracic motion and 2° of glenohumeral motion. For example, shoulder flexion of 180° would be calculated as 120° of glenohumeral movement and 60° of scapulothoracic movement. To maintain pain-free scapulohumeral rhythm, the muscles and their movements must remain normal and in good-length.