Now into the fourth decade of widespread clinical acceptance and use, joint replacement surgery has had a major impact on the preservation of physical independence and general health in the ageing population. However, today's data are tomorrow's history. Rather than tell clinicians and patients what they might expect today from yesterday's procedure, this chapter surveys the role of joint replacement in the treatment of degenerative disease, assesses the associated fiscal burden on society and notes the significant gaps in our current knowledge. Strategies and approaches for future study are critically reviewed.