Kneecap resurfacing should become standard in knee replacement, 20-year trial suggests

The longest randomised controlled trial in knee orthopaedics found that resurfacing the kneecap during total knee replacement delivers greater long-term health benefits at no additional cost, strengthening the case for making the procedure routine.

A 20-year clinical trial involving more than 1,700 patients has found that resurfacing the kneecap during total knee replacement is likely to offer the best long-term value for patients and healthcare systems, prompting researchers to call for the procedure to be considered standard practice.

The findings come from the Knee Arthroplasty Trial (KAT), conducted by researchers from the University of Oxford and the University of Aberdeen. Published in The Lancet, the study is described as the largest and longest randomised controlled trial ever undertaken in knee orthopaedics.

The results are significant because total knee replacement is among the most commonly performed orthopaedic procedures. While the operation is generally considered highly successful, up to one in five patients continue to experience pain or reduced function after surgery. Researchers say many of these poorer outcomes may be linked to the interaction between the kneecap and the underlying knee implant.

What is kneecap resurfacing?

Kneecap resurfacing is a surgical technique performed during total knee replacement. The procedure involves replacing the damaged underside of the kneecap with a smooth artificial surface. Whether this should be carried out routinely has remained a matter of debate for years, leading to considerable variation in surgical practice across the United Kingdom and internationally.

The KAT study compared patients who underwent kneecap resurfacing during knee replacement surgery with those whose kneecap was left unchanged.

Small differences, consistent advantage

Researchers found that both groups experienced good long-term outcomes. The study reported little difference between the two approaches in major clinical measures, including knee function, complication rates and the need for additional surgery.

However, most outcome measures showed a small but consistent advantage for patients who received kneecap resurfacing.

When patient benefits and healthcare costs were assessed together, resurfacing emerged as the option most likely to provide the best value over the long term.

“Our results suggest that replacing the kneecap produces more health benefits at no extra cost,” said Associate Professor Helen Dakin of Oxford Population Health.

Evidence for more consistent practice

The study was funded by the National Institute for Health and Care Research (NIHR) and supported by the NIHR Biomedical Research Centre, Oxford.

According to Professor David Murray of the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS) at the University of Oxford, nearly every measure in the trial favoured kneecap resurfacing, even though the differences in clinical outcomes were relatively small.

“Over 20 years resurfacing the kneecap provided more health benefits for the patients,” Murray said, adding that surgeons should now consider kneecap resurfacing as part of standard care for most people undergoing total knee replacement.

Professor Marion Campbell of the University of Aberdeen said the findings provide robust evidence to support wider and more consistent use of kneecap resurfacing in knee replacement surgery.

She noted that the results could help reduce variation in surgical practice, particularly given the large number of knee replacement procedures performed each year across the National Health Service (NHS).

Long-term implications

A randomised controlled trial is considered one of the strongest forms of clinical evidence because it directly compares treatment approaches in similar patient groups over time.

The KAT study adds two decades of follow-up data to a long-running debate in orthopaedic surgery. While both surgical approaches remain effective, the findings suggest that routinely resurfacing the kneecap during total knee replacement may provide additional patient benefit without increasing costs, offering a compelling case for broader adoption in clinical practice.