blog post 3

The scapulohumeral rhythm is defined as the ratio of movement between the scapula and the humerus. This interaction is important for optimal movement of the shoulder. It is crucial for the scapula and humerus to work together. A dysfunction will occur if normal position of the scapula to the humerus changes. Also, the scapula works around rotations to the thorax. For full ROM, the humeral head must rotate laterally. Another important fact is that the glenohumeral joint is needed for efficient arm movement.

The scapulohumeral rhythm permits good length-tension relationships. It affects the ROM measurements of the shoulder by every 3 degree of shoulder movement, there is a 1 degree at the scapulothoracic joint and 2 degree at the glenohumeral joint. For example, for full 180 degree of motion there would need to be 60 degrees at the scapulothoracic joint and 120 degrees at the glenohumeral joint. This ratio is defined as a 2:1 movement between the glenohumeral joint and the scapulothoracic joint. If the individual has a properly coordinated scapulothoracic rhythm, there will be about 120 degrees of glenohumeral abduction and 60 degrees of shoulder upward rotation.