Scapulohumeral Rhythm

The clinical relevance of the scapulohumeral rhythm is that it plays a major role in the function of the shoulder.  Due to the complexity of this rhythm, it can greatly affect ROM measurements/movements of the shoulder.  Firstly, the ratio of movement between the scapula and humerus must be addressed.  For full 180 degrees of motion, the scapula moves 60 degrees, and the humerus moves 120 degrees.  When dysfunction occurs, abduction of the glenohumeral joint can be affected.  This is prevalent in when someone tries to lift their shoulder and there is a large substitution in trunk flexion to try and lift the arm up into the air.  The scapula is controlled greatly by the serratus anterior muscle, and if the muscle is not working properly, the scapula may wing, which would cause the shoulder to not be able to lift and may cause impingement or rotator cuff problems.  The scapulohumeral rhythm also allows for good length-tension relationship, so if a problem occurs with the rhythm, such relationship may be affected as well.