Scapulohumeral Rhythm

The "Scapulohumeral Rhythm" is the ratio of movement between the scapula and the humerus. This movement is very important for range of motion and giving us 3 degrees of movements. In most individuals, the general rule, is that for every 3 degrees of shoulder movement, there is 1 degree of movement at the scapulothoracic joint and 2 degrees of movement at the glenohumeral joint. For individuals to achieve full range of motion, the head of the humerus must laterally rotate. This must occur equally between the two joints and synchronously to allow for full range of motion. These two joints must actively work together to ensure no friction is occurring that could cause damage to the bones, muscles, tendons, nerves, and blood supply. If the scapula does not upwardly rotate properly, the subacromial space will be limited and impinged. For full 180 degrees of shoulder movement, an individual will have 60 degrees from the scapulothoracic joint and 120 degrees from the glenohumeral joint. We need this full range of motion to be able to do basic ADL's like combing our hair, putting a shirt over our head, and scrubbing our back in the shower.