Biomechanics Blog 3: Scapulohumeral Rhythm

Scapulohumeral Rhythm describes the synchronized movement between the scapula and humerus. This movement is defined by a ratio. The general rule for scapulohumeral rhythm is that for every 3 degrees of shoulder movement, there is 1 degree at the scapulothoracic joint and 2 degrees at the glenohumeral joint. This means if the full range of motion of a client's shoulder was 180 degrees, the practitioner would divide 180 from 3 and that would get the degree for the scapulothoracic joint (this would be 60 degrees). However, if the practitioner wanted the degree for the glenohumeral joint, they would divide 180 from 3 then multiply that number by 2 (this would be 120 degrees).

Scapulohumeral Rhythm is very relevant in the clinical aspect. The shoulder, which is made up from the scapula, humerus, and clavicle, has the greatest range of motion (ROM) in the body compared to any other joint. Scapulohumeral rhythm is associated with abduction or elevation of the shoulder. Therefore, the optimal function and ROM of the scapula and humerus are important, especially when it comes to everyday activities such as reaching to grab something, brushing your hair, to even putting on or taking off a shirt. With scapulohumeral rhythm, the motion allows the shoulder to function without any pain, because it decreases the shear forces between the joints. However, if the scapulohumeral rhythm becomes abnormal, this can tell us potential shoulder injuries or impingements that the client may have. By knowing that a client has a potential impingement or shoulder injury due to an abnormal scapulohumeral rhythm, the practitioner can carry out the right interventions or exercises that could work on strength and stabilization to help improve the rhythm so that the client's shoulder can function normally and pain-free.

Retrieved from:(clipart-library.com)