Scapulohumeral Rhythm

The scapulohumeral rhythm is the relation of the scapula and humerus during shoulder movement. There is a ratio, 3:2:1, to note when looking at these mechanics. For instance, if there is 150 degrees of shoulder abduction, then there is 100 degrees of movement at the humerus and 50 degrees of movement at the scapula. This rhythm is important for several reasons. A broad reason is a universal communication between the OT family. An example of this is if an occupational therapist tells another OT that client A has 120 degrees of movement at the glenohumeral joint then the other therapist will automatically be able to know what the degrees of motion at the scapula is, as long as the client is not having any complications in that area. Another main purpose of this rhythm is it allows full range of motion at the shoulder joint. In addition, it also allows the glenohumeral joint to be more steady when strong forces are acted upon it. This is called length-tension relationship. It allows for certain occupations to be completed without injury to the shoulder. Consequently this whole process can be a hinder to some. If one part of this process gets injured, then it will affect the ability of the rest of the rhythm to move in full ROM. So, the scapulohumeral rhythm is important for communication across the OT world, allowing full ROM, keeping the glenohumeral joint steady, providing better length-tension relationship, and pointing out any abnormalities of shoulder movement.