Scapulohumeral Rhythm

    Scapulohumeral rhythm is the coordination between the scapula and humerus in shoulder elevation.
It is important that the glenohumeral and scapulothoracic joint are working congruently with one another in order to have a full range of motion. To have a normal scapulohumeral rhythm, it is necessary for the scapula to rotate upward, which will ensure that the glenoid fossa stays aligned with the head of the humerus. This results in a decrease in shear forces between the humerus and scapula.(1) As the scapula is changing into this position, the humerus can then laterally rotate.  Without the scapula's upward rotation, the glenohumeral muscles would not be able to withstand the force it takes to have a full range of motion. (2) If both of these joints are moving simultaneously, there is a decrease of likelihood for impingement. (3)
      As a therapist, it is important to know that for every 3 degrees of shoulder movement, there is 1 degree at the scapulothoracic joint, and 2 degrees at the glenohumeral joint. As a therapist measures his/her client's ROM, he/she must take note of these ratios. If the client is having a difficult time reaching full ROM, you can measure to see exactly which joint is lacking the appropriate degree. (4) This can help to narrow down the issue and to properly treat the client. Also, if a client reports pain and decrease shoulder function, it would be relevant to assume that there is an inconsistency in the scapulohumeral rhythm. (5)