Question

which of the following motions happen at the glenohumeral joint during external rotation?

a) anterior roll, posterior glide

b) posterior roll, anterior glide

c) inferior roll, superior glide

d) superior roll, inferior glide

Explanation:

To determine the correct motion at the Glenohumeral joint during external rotation, we recall the arthrokinematics of the shoulder. During external rotation, the humeral head (at the Glenohumeral joint) undergoes a posterior roll and an anterior glide. This is based on the principles of joint mechanics where roll and glide directions are related to the axis of rotation and joint surface movements. Option a has incorrect directions, options c and d relate to vertical (inferior/superior) movements which are not the primary arthrokinematics for external rotation. Option b (Posterior roll, anterior glide) matches the known arthrokinematic movements for external rotation at the Glenohumeral joint.

Answer:

b) Posterior roll, anterior glide