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

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.

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.