Normal shoulder function requires smooth integration of the following joints; glenohumeral joint, scapulothoracic, acromioclavicular, and sternoclavicular joint. This movement from the shoulder is referred to as the “Scapulohumeral Rhythm” and is required for full limb elevation. It should be smooth, coordinated, and symmetrical. A dysfunction in any of the above joints will result in altered or jerky movements. The dysfunction can be caused from previous injuries, weakness, poor motor control of scap stabilizers, or involuntary movement to avoid a painful range.
Muscles that control the scapula and are involved in this rhythm are the following; trapezius, serratus anterior, rhomboids, levator scapulae and pectoralis minor. These muscles work in co-ordinated “force couples” to control movement of the scapula. The first phase of shoulder movement starts with the scapula being set and referred to as the setting phase. In the second phase, there is a ratio of 2:1. For every 2 degrees of glenohumeral joint motion there is 1 degree of scapulothoracic motion, for a total range of 180 degrees in the shoulder.
Below is a link to a healthy and smooth functional shoulder.
Below is a link to an unhealthy shoulder referred to as scapular dyskinesis.
If you have any questions regarding the above material, have pain in your shoulder or feel that you can’t get full shoulder range of motion, contact one of the therapist at Lawrence Park Health.
Author: Khanh Vy
Registered Kinesiologist | Certified Athletic Therapist (R.KIN(CAT)) | Certified Strength and Conditioning Specialist (NSCA-CSCS)1 Like