A) Adhesion of the distal plexus may result in axillary nerve irritation because of differential motion at the quadrangular space through which it passes after a short distance of travel. Patients often present with failed rotator cuff surgery undertaken for shoulder pain that has been misdiagnosed. The axillary nerve syndrome presents with pain in the axillary nerve distribution over the shoulder joint and deltoid weakness.

B) Shoulder of a 17 year old tennis instructor with shoulder pain and difficulty positioning his arm for his serve. The axillary nerve (ax) is seen arching out across the neck of the humerus (hu) after branching off the posterior cord (pc) of the brachial plexus at the origin of the radial nerve (rn) (the beaded appearance of the axillary nerve in this 3D projection image is an artifact of the slice spacing).