Do Knee Replacements Continue to Provide Relief to Patients in the Longer Term?

Total knee arthroplasty is one of the most common orthopaedic operations and has proven to have a profound effect on improving the health and well-being of patients. Patient-reported outcome measures (PROMs) have become increasingly important for assessing patients’ perspectives on the success of their surgery and are now considered integral metrics of surgical outcomes, particularly in the context of value-based health care. As a result, considerable resources are currently being directed toward obtaining the serial PROM scores of patients undergoing knee replacement. The majority of studies reporting on long-term PROM scores for knee replacements have assessed scores up to 10 years postoperatively. These studies have mostly suggested that, after an improvement in PROM scores in the first couple of years, there is a plateau and then a general decline in these scores over time. Therefore, the merits of spending resources on long-term PROM score collection and the clinical value of such scores have been questioned1,2. Choi et al. have to be congratulated for going beyond the usual 10-year PROM scores by analyzing PROMs at the 15-year mark in a reasonably large sample size (n > 400). They looked at both disease-specific PROMs (the Knee Society Knee Score, Knee Society Function Score, and Western Ontario and McMaster Universities Osteoarthritis Index) and generic health-related PROMs (the Short Form-36 SF-36). Like previous studies, they found an initial improvement in PROM scores across the cohort. Subsequently, the disease-specific PROM scores remained relatively stable until 5 years, after which some of the scores continued to stay stable while others showed variable degrees of decline, with some showing statistically insignificant changes, some showing statistically significant declines that were not clinically meaningful, and some demonstrating clinically meaningful declines. The various domains of the generic PROMs showed more variable trajectories: all subscales showed statistically significant or clinically meaningful improvements within the first 6 months, after which some continued to improve up to 5 years, some remained stable up to 5 years following the initial improvement, and a few others declined after an initial improvement in the first year. After 5 years, there was a general decline in the various generic PROM scores over the longer term; however, all of the scores at 15 years stayed substantially higher than baseline. In fact, the scores for the SF-36 social functioning domain continued to improve throughout the 15-year follow-up, although not all of the changes between the different time points were statistically significant. The authors acknowledged 2 key drawbacks to their study. First, they did not have a control group, which therefore makes it difficult to isolate the long-term PROM score trends that are attributable to the surgery from those that are attributable to natural age-related progression. Second, the study cohort was quite specific, consisting mainly of female Korean patients, which makes it difficult to generalize the trends to other groups. Nevertheless, the study provides some reassurance that knee replacements appear to have a degree of continued positive effects on patients over a long period of time. While this paper may not put to bed the debate of whether long-term PROM scores are useful to collect beyond the early years, it provides further confirmation that knee replacements provide long-term benefits to patients, as perceived by the patients themselves.