Arc-aggregation: a new method of range of motion analysis in hemophilia

Arc-aggregation is a new graphic method of analysis of progressive loss of range of motion that can be applied to any diarthrodial joint undergoing a specific degenerative process. It is based on the premise that loss of motion (LOM) for a specific condition occurs in a predictable way or pattern. Using this method to analyze a population of 48 hemophilic patients with various stages of joint involvement, we studied 95 knees, 93 ankles, and 83 elbows for a total of 271 joints. We found a predictable pattern of progressive loss of range of motion for each joint. To detect the early onset of joint involvement, the first LOM is important. The early loss with the knee was in flexion, which gravitated toward fusion at 40 degrees. For the elbow, the early LOM was extension with fixation, occurring at 90 degrees of flexion, the preferred position for fusion. For the ankle, the early LOM was dorsiflexion with final ankylosis in slight equinus.