Which of the following best describes motion at the sternoclavicular (SC) joint?
a. During clavicular elevation and depression, the disc of the SC joint moves with the medial end of the clavicle on the manubrial facet.
b. During clavicular protraction and retraction, the disc of the SC joint moves with the medial end of the clavicle on the manubrial facet.
c. During clavicular elevation and depression, the lateral end and medial end of the clavicle move in the same direction.
d. During clavicular protraction and retraction, the lateral end and medial end of the clavicle move in opposite directions.
ANS: B
The articular disc of the SC joint separates the joint into two separate cavities. During elevation/depression, the medial end of the clavicle moves on the rather stationary disc. However, during protraction/retraction, the disc and clavicle move on the manubrium as one unit. This adds to the ability to use convex/concave rules to this unusual saddle joint.
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