Scapulohumeral Rhythm

The scapulohumeral rhythm is the ratio of movement between the scapula and the humerus which is clinically relevant for many reasons. Some of these reasons being that it plays a huge part in the ROM of the shoulder and it allows 180 degrees of motion by assisting the movement between the scapula and the humerus. This includes assisting the humeral head to rotate laterally to get the greater tubercle out of the way of the coracoacromial arch, in order to achieve the full ROM. The scapulohumeral rhythm also allows optimal length-tension relationships (generally the midpoint ROM) between the muscles involved in this action which is considered to be the ideal length of a muscle. Along with this, the scapulohumeral rhythm increases joint congruency which in turn decreases shear forces and plays a part in allowing full ROM of the shoulder. The scapulohumeral rhythm directs the correct positioning of the humeral head (convex surface) to be placed on the glenoid fossa (concave surface), which can have an affect on the ROM measurements of the shoulder. If these are incorrectly aligned or not moving as they should be, the measurements of ROM of the shoulder will likely be measured as less than the full ROM (less than 180 degrees). The scapulohumeral rhythm is important for efficient arm movement and this is something that therapists need to be aware of in order to determine a treatment plan for each individual client.