Early studies of hip replacement showed that the operation was associated with large and sustained QALY gains, and hence that it was cost-effective. The same applied to knee replacement. The patients in these studies all had severe disease, as shown by their quality of life scores at baseline. But indications for both operations have gradually expanded so that the majority of current patients who receive the operation are atypical of those in the original studies. That is to say, their disease is less severe. The long-term benefits of hip replacement have been found to be modest in recent studies, doubtless because patients with less severe disease have less capacity to benefit. Now a large American study  has reported similar findings with respect to knee replacement, confirming that the operation is only cost-effective in people with severe pain and limitation of movement at baseline. As in many medical/surgical treatments it is important to stratify by baseline severity. Absolute (and sometimes relative) benefits fall as baseline severity decreases, thereby radically shifting the harm to benefit ratio.
— Richard Lilford, CLAHRC WM Director
- Beswick AD, Wylde V, Gooberman-Hill R, Blom A, Dieppe P. What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients. BMJ Open. 2012; 2: e000435.
- Ferket BS, Feldman Z, Zhou J, et al. Impact of total knee replacement practice: cost effectiveness analysis of data from the Osteoarthritis Initiative. BMJ. 2017; 356: j1131.