The Acromioclavicular (AC)joint Contributes to Shoulder Elevation ____________________

The acromioclavicular (AC) joint contributes to shoulder elevation ____________________.

A) between 30° and 90° of abduction when tension on the trapezoid component of the coracoclavicular ligament produces a posterior rotation of the clavicle
B) after 90° of shoulder abduction and until all scapulothoracic motion is taken up
C) between 30° and 90° of abduction when anterior rotation of the clavicle allows for 30° of scapular upward rotation
D) after 60° of abduction