During arm elevation, what is the typical scapulohumeral rhythm ratio of scapular upward rotation to glenohumeral elevation?

• A. 2:1
• B. 1:2
• C. 1:1
• D. 3:1

Answer: (A)

During arm elevation, movement is shared between the glenohumeral joint and the scapulothoracic (scapular upward rotation) component in a consistent rhythm. About two-thirds of the elevation comes from the glenohumeral joint, and about one-third comes from scapular upward rotation. For full elevation (roughly 180 degrees), this translates to approximately 120 degrees at the glenohumeral joint and about 60 degrees from the scapula, giving a ratio of scapular upward rotation to glenohumeral elevation around 1:2. In practice test wording, this is often described as the rhythm of motion being two parts at the glenohumeral joint for every one part of scapular motion, i.e., a 2:1 relationship when the order is glenohumeral to scapular motion. The key takeaway is that the shoulder’s elevation is balanced with a smaller, proportional contribution from scapular upward rotation.