 The bursa therefore inflates, producing a swelling over the proximal end of the ulna which is usually inflamed and tender.Another possible cause of inflammation of the bursa is infection, which can usually (but not always) be traced to a crack or other lesion in the skin which allowed for bacteria of the normal skin flora to invade deeper layers of tissue.This bursa is located just over the extensor aspect of the extreme proximal end of the ulna.