Scapulohumeral Rhythm

 Scapulohumeral rhythm is a term used to describe the movement between the scapula and humerus in order to maintain contact between the two during movement, especially shoulder elevation. More specifically, it describes the ratio of movement between the scapulothoracic joint and the glenohumeral joint. The ratio for this movement is 2:1; meaning that for every 1 degree of movement at the scapulothoracic joint there is 2 degrees of movement at the glenohumeral joint. 

So why does this matter? 

There are many different clinical relevancies of scapulohumeral rhythm. One being that you can observe this rhythm on a client by palpation as you have them elevate their shoulder, and you will notice that scapulothoracic joint does not move as much as the glenohumeral joint; hence the 2:1 ratio. Also, scapulohumeral rhythm allows for a better length-tension relationship in the prime movers of shoulder movements. Therefore, scapulohumeral rhythm plays a role in full ROM of the shoulder joint, so having knowledge of this as an OT will allow you to possibly understand why a client does not reach the normal range for ROM for a particular movement. Impingement is also something that you may deal with in some clients, so it is important to know that scapulohumeral rhythm is what prevents this from happening if everything is functioning properly.  Lastly, it is important for practitioners to be able to identify proper and improper scapulohumeral rhythm in order to recognize potential problems within their clients.

All of this to say that if scapulohumeral rhythm did not exist, movement at your shoulder as we know it would be possible due to the inability of the humerus to remain in contact with the glenoid fossa.