Question

All of the following movements occur during abduction of the shoulder, except:

• A. Elevation of humerus
• B. Axial rotation of clavicle
• C. Medial rotation of scapula
• D. Acromioclavicular joint movement

Hint:

During abduction the glenoid must turn upward, so which direction does the scapula really rotate?

Answer 1

The Correct Option is C

Step 1: Full abduction of the upper limb to 180 degrees is not a single joint action. It is a combined movement of the glenohumeral joint and the shoulder girdle, described by the scapulohumeral rhythm (about 2 degrees of glenohumeral movement for every 1 degree of scapular movement).

Step 2: What happens during abduction. The humerus elevates and rotates laterally at the glenohumeral joint (option A occurs). The scapula rotates so that the glenoid cavity turns upward; this is lateral (upward) rotation of the scapula, not medial rotation. To allow scapular rotation, movement must occur at the sternoclavicular and acromioclavicular joints (option D occurs).

Step 3: During this scapular rotation the clavicle also rotates about its own long axis (axial rotation of the clavicle, the so-called crankshaft mechanism at the sternoclavicular joint), so option B occurs.

Step 4: The exception is option C. The scapula undergoes lateral rotation during abduction, so describing it as medial rotation of scapula is the incorrect statement and is the answer to this except question.

Answer: C. Medial rotation of scapula