Biomechanics Post 3

Scapulohumeral rhythm is the relationship between the movement of scapula and the humerus. It is the ratio between the movement of these two bones. The shoulder has 3 degrees of movement. Two of those degrees are for the humerus and the remaining one is for the scapula. For example, if the humerus moves 120 degrees then the scapula moves the remaining 60 degrees. Scapulohumeral rhythm is essential in allowing full ROM. It allows for full muscle length tension and is needed for efficient arm movement. 

This rhythm permits good length tension relationships allowing for efficient arm movement. Scapulohumeral rhythm decreases shear forces allowing for improved joint congruency. This rhythm involves maintaining subacromial space and decreasing the likelihood of shoulder impingement. This is very important clinically in order to obtain accurate range of motion measurements.Since they work together, the therapist should stabilize the scapula in order to measure the glenohumeral joint range of motion. The shoulder and the scapula work together help to prevent active insufficiency.