You may have heard the term Scapulohumeral rhythm in reference to good shoulder movement, but what is it exactly and how does it relate to shoulder function.
Shoulder motion occurs through dynamic control of several joints that is made up of the scapula, clavicle, and humerus as well as the small and large muscles that attach. The joints are the articulation of the acromioclavicular joint (where the scapula connects to outside of clavicle) and glenohumeral joint (the ball and socket of humerus and scapula) as well as a “false joint” as there is not actual bony articulation called the scapulathoracic joint where the shoulder blade slides across the thoracic spine.
As we elevate our arm there is an upward motion that is roughly 1/3 the movement at scapula thoracic joint and 2/3 at the glenohumeral joint. The coordination and timing of these movements make up the rhythm. A good scapulohumeral rhythm helps preserve the length tension relationship of the muscles around shoulder blade. As the scapula moves upward the muscles around rotator cuff can sustain force through end of range movements such as overhead reaching.
Abnormalities in this movement are common and while they can be pain free and cause no issue it often a sign of poor muscle control and coordination that can lead to shoulder pain, rotator cuff issues, or can be seen after injury has already occurred.
Poor shoulder blade movement is often seen as forward tipping and rotation of scapula that can cause pressure of the structures that sit underneath such as the rotator cuff muscles or bursa. Therefore, as person lifts their arm they feel pinch and pain around shoulder blade.
Altered scapulohumeral rhythm can be addressed and corrected. Exercises and mobility that focuses on the thoracic spine can help improve the slide of the scapula as it moves upward as these exercise addresses the rounded rib cage long periods of sitting can create. Further, we want to strength the muscles that support healthy overhead movement. Scapula winging, where the shoulder blade slides excessively away from ribs may be a result of reduced strength of the serratus anterior muscles and shortening of the pectoralis muscles.
Over time exercises and training of the scapulohumeral rhythm can become more dynamic and complex. As the individual starts to demonstrate better control they will be able to engage in activities like throwing and overhead sports with a reduced injury risk and pain free shoulder elevation.
