Fracture through a geode in the proximal ulna.

Chronic joint pain in rheumatoid arthritis may mask that from other causes. Stress fractures, particularly in osteoporotic lower limb bones of such patients, are well described but can still cause diagnostic difficulty. These difficulties were highlighted by a case in which an unusual fracture occurred through a geode in the proximal ulna mimicking an exacerbation of synovitis in the elbow joint.