Scapulohumeral Rhythm
Table of Contents
What Is Scapulohumeral Rhythm
Scapulohumeral Rhythm is the synchronized movement between the scapula and the shoulders during shoulder elevation. There are two main joints involved in this relationship, the glenohumeral joint and the scapulothoracic joint. Together these joints are what create movement of the shoulder. This interaction is important for the healthy functioning of the shoulder.
Scapulohumeral Rhythm Is Affected By
Scapulohumeral Rhythm is affected by the glenohumeral joint and the scapulothoracic joint. The glenohumeral joint is the articulation between the head of the humerus and the glenoid fossa of the scapula. The scapulothoracic joint is the articulation between the anterior surface of the scapula and the posterior thoracic cage. When both of these joints are functioning properly, full shoulder elevation to 180 degrees is possible. Abnormal functioning or either joint can affect Scapulohumeral Rhythm and is indicative of muscular or joint dysfunction.
Abnormal Scapulohumeral Rhythm
When the relationship between the glenohumeral joint and the scapulothoracic joint is not functioning properly, the dysfunction of the Scapulohumeral Rhythm can occur. This can result in pain, clicking, and instability in the shoulder. Your doctor can perform a physical assessment to determine if there are abnormalities in the shoulder. A change in the normal position of the scapula relative to the humerus is also called Scapular Dyskinesia.
Scapulohumeral Rhythm Ratio
Generally, the first 30 degrees of shoulder abduction comes from the glenohumeral joint. The scapula remains stationary during this time. Beyond 30 degrees of shoulder abduction, the scapula becomes involved with its inferior angle shifting outwards as it begins to rotate superiorly. On average, the Scapulohumeral Rhythm has a 2:1 ratio; for every two degrees of glenohumeral movement, there is one degree of scapulothoracic movement in healthy adults. For example, if the arm is abducted to 90 degrees, this was completed using 60 degrees of glenohumeral movement and 30 degrees of scapulothoracic movement.
Reverse Scapulohumeral Rhythm
This occurs in shoulders with reverse total shoulder arthroplasty (RTSA). RTSA is a surgical procedure used to address rotator cuff tears and various conditions which involve the dysfunction of the rotator cuff. Typically, individuals who have undergone an RTSA will have changes in scapular position and show more upward rotation of the scapula. Studies have found the motion of the scapula and the shoulder to be different in individuals who have RTSA than normal with scapulohumeral rhythm lower due to more scapulothoracic movement and less glenohumeral movement to elevate the arm.
Scapulohumeral Rhythm Muscles
The muscles that connect the scapula to the humerus are called the scapulohumeral muscles. These are a large group of muscles that allow for shoulder adduction, shoulder abduction, external and internal rotation, flexion, and extension. Each muscle has its specific function as well as nerve and blood supply and they work together to contribute to scapulothoracic stability and motion. It is imperative to train these muscles properly to maintain a healthy Scapulohumeral Rhythm and avoid disease or injury.
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Scapulohumeral Rhythm Exercises
Any exercises that work on scapular stabilization and strength will help to improve your scapulohumeral rhythm. Take a look at some of the example exercises below, and check out our article on Winged Scapula for more scapular stabilization exercises!
Scapular Wall Slides
Begin with your back, head and neck against a wall and your feet roughly a step in front of the wall. Your knees can be slightly bent. Raise both arms so they are flat against the wall with a 90-degree bend at the elbow. Keeping your arms pressed against the wall, begin to slide them upwards so your arm is fully extended. You should aim to end up forming a ‘Y’ shape with your arms. Return to starting position and repeat for 2-3 sets of 15-30 reps.
Mini Band Wall Walks
Begin facing a wall with a resistance band looped around both wrists. Place your forearms on the wall with your elbows at shoulder height. Raising one arm at a time, begin to walk your forearms up the wall until your elbows are around eye level. Walk back down the wall to return to starting position and repeat for 2-3 sets of 5 walks up and down the wall. Remember to keep the shoulders down and back when performing this exercise.