Scapulohumeral Rhythm

Scapulohumeral rhythm is the movement between the scapula and the humerus. The scapulohumeral rhythm is also important for aiding in aligning the head of the humerus with the glenoid fossa. The rhythm between the two is very important to have a shoulder movement that is able to perform full range of motion at the glenohumeral and scapulothoracic joint. Functionality with both of the joints  creates a good length-tension relationship. There are 3 degrees of freedom that happen in the scapulohumeral rhythm. The scapula should move 60 degrees and the humerus should move 120 degrees. In total, this permits a full 180 degrees of motion, which would be considered full range of motion at the glenohumeral and scapulothoracic joints. This ratio is a 2 to 1 ratio. Knowing this information is important for clinical relevance. In any type of clinic for measuring range of motion, knowing these degrees of freedom and their importance allows you to measure the functionality at the joint. Not only are degrees of freedom important, but it is also important that the humeral head has the ability to rotate laterally to reach full range of motion. Motion could also be disrupted at either one, or two of the joints. When this happens, it results in increased shear forces. Overall, the shoulder has a dynamic relationship between the scapula, humerus, glenohumeral and scapulothoracic joints. If able to work in a functioning "relationship", full range of motion can be achieved and measured. If one part to the whole "relationship" is messed up, range of motion and functionality will be hindered.