Biomechanics #3

Scapulohumeral rhythm is important in regards to clinical practice because it is the ratio of movements between the scapula and the humerus. It gives the practitioner knowledge of if the humerus is moving so many degrees, then you can deduce how much the scapula is moving. Generally, for every 3 degrees of shoulder movement, then there is 1 degree at the ST joint and 2 degrees at the GH joint. It is the movement of the shoulder complex, which includes all structures and muscles, all together at once. This is important because if there is damage or trauma to one part, or one muscle, it will directly effect the ability of the other muscles to work properly. It can effect the range of motion in the shoulder because there won't be a full range of motion in the shoulder in specific movements when certain muscles have been effected. In order to obtain full range of motion in the shoulder, which is roughly 180 degrees, the humeral head must rotate laterally. When it rotates and reaches full ROM, the ST joint has moved 60 degrees and the GH joint has moved 120 degrees. This demonstrates the ratios of movements and scapulohumeral rhythm.