The largest and longest clinical trial of its kind – published in The Lancet – has found that resurfacing the kneecap during total knee replacement is likely to be the most cost-effective approach for patients and healthcare systems over the long term, reports MedicalXpress.
Researchers from the University of Oxford and the University of Aberdeen followed more than 1 700 patients for 20 years as part of the KAT (Knee Arthroplasty Trial) study, making it the longest randomised controlled trial ever conducted in knee orthopaedics.
Total knee replacement is one of the most common and effective operations performed in the NHS. Although it is generally highly successful, up to one in five patients will continue to experience pain or reduced function after surgery. Many of these poor results are thought to relate to movement between the kneecap and the underlying knee replacement.
One potential solution is kneecap resurfacing, which involves replacing the damaged underside of the kneecap with a smooth artificial surface during knee replacement surgery. However, whether surgeons should routinely perform this procedure has long been debated, and practice varies widely both within Britain and internationally.
The KAT study compared outcomes for patients who had kneecap resurfacing (replacing part of their kneecap) during their knee replacement operation with those who had knee replacement without any change to the kneecap.
The study found that both approaches had good outcomes over the long term, with little difference between the two groups in long-term clinical outcomes, including knee function, complications and rates of further surgery. However, most measures showed a small but consistent trend in favour of kneecap resurfacing
When costs and patient benefits were considered together, resurfacing the kneecap was very likely to offer the best value for the NHS.
David Murray, Professor of Orthopaedic Surgery at the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS) at the University of Oxford, said: “This is the largest and longest study ever undertaken to examine whether the kneecap should be resurfaced during total knee replacement. Although the differences in clinical outcomes were small, nearly every measure consistently favoured resurfacing.
“As a result, over 20 years, resurfacing the kneecap has provided more health benefits for patients. Given these findings, we believe surgeons should now consider that as part of standard care for most patients undergoing total knee replacement.”
Associate Professor Helen Dakin from Oxford Population Health added: “Our results suggest that replacing the kneecap produces more health benefits at no extra cost.”
Professor Marion Campbell from the University of Aberdeen noted: “The results provide robust evidence to support more consistent use of kneecap resurfacing in knee replacement surgery and could help reduce variation in surgical practice.”
Study details
Patellar resurfacing in total knee replacement: 20-year clinical and economic results of a large multicentre, randomised controlled trial in the UK
David Murray, Jemma Hudson, Helen Dakin et al.
Published in The Lancet on 17 June 2026
Summary
Background
There is conflicting evidence regarding the merits of patellar resurfacing during total knee replacement (TKR), as previous randomised controlled trials (RCTs) have been under-powered and with follow-up of 10 years or less.
Methods
A pragmatic, multicentre, open-label RCT was initiated in 1999 in the UK. Within a partial-factorial design, participants were randomly allocated to receive or not receive patellar resurfacing during primary TKR and were followed up for 20 years. Adult (aged ≥18 years) patients due to have a primary TKR under the care of a collaborating surgeon were eligible. Participants were allocated (1:1) using an automated telephone service stratified by surgeon, with minimisation according to the patients’ age (<60 years, 60–79 years, ≥80 years), sex, and location of disease. The primary outcome measure was the Oxford Knee Score (OKS), analysed using repeated measures mixed-effects linear regression analysis with marginal differences reported. Secondary measures included the 12-Item Short Form Health Survey (SF-12), the European Quality of Life 5-Dimensions 3-Levels (EQ-5D-3L), costs, cost-effectiveness, and subsequent knee surgery.
Findings
Between April 8, 1999, and Jan 13, 2003, 1715 participants (955 female and 760 male; mean age 70 years [SD 8], mean BMI 29·7 kg/m2) were randomly assigned: 861 to patellar resurfacing and 854 to no resurfacing. At the 20-year follow-up, 132 participants in the patellar resurfacing group and 110 participants in the non-resurfacing group provided outcome data, although marginal differences included earlier data for participants who died or had missing 20-year data. The marginal difference in OKS over the whole 20-year follow-up was 0·76 (95% CI –0·08 to 1·59; p=0·076) in favour of patellar resurfacing. During the 20-year follow-up period, although not significant, differences in OKS, SF-12, and EQ-5D-3L, readmissions, minor or intermediate operations, patella-related operations, major operations, and complications all favoured patellar resurfacing. At 20 years, the resurfaced group accrued significantly more quality-adjusted life-years (QALYs) than the non-resurfaced group (7·295 vs 6·884; difference 0·380, 95% CI 0·061 to 0·700; p=0·020). However, QALY differences were smaller in a sensitivity analysis assuming no difference in mortality (7·209 vs 6·964; difference 0·183, 95% CI –0·034 to 0·400; p=0·10). The cost of readmissions was non-significantly lower in the resurfaced group and offset the higher cost of primary TKR; therefore, overall 20-year health-care costs per participant were similar (£10 825 vs £10 889; difference –£6, 95% CI –£721 to £708; p=0·99).
Interpretation
There was no significant difference in primary outcome (OKS) or other clinical endpoints. However, as clinical differences tend to support patellar resurfacing, the resurfacing group had significantly higher QALYs. There was no difference in costs over the 20-year period, and patellar resurfacing had a 99% probability of being cost-effective at any threshold above £10 000 per QALY gained. The evidence is therefore weighted towards resurfacing being the approach of first choice.
See more from MedicalBrief archives:
Younger knee replacement patients more likely to require re-operation
Survival data on hip and knee replacements from 6 countries over 25 years
Reuse single-use items to slash surgery carbon footprint – UK study