When it comes to total knee arthroplasty, the patella remains one of the most debated elements of the procedure: should the kneecap (patella) be resurfaced or left alone? Despite decades of research, no definitive answer has emerged.
The information presented in this article is drawn from a comprehensive study titled No difference in revision rate in patella-friendly total knee arthroplasty with or without patella resurfacing at 5 years’ follow-up. A database analysis, published in the Journal of Experimental Orthopaedics by Massardier, Manchec, Bérard, Lustig and Professor Etienne Cavaignac.
This large-scale analysis, covering over 6,000 procedures performed across 16 centres in France between 2002 and 2018, offers valuable insights for both patients and clinicians seeking clarity on this long-standing debate.
What is patellar resurfacing and why does it matter?
During a total knee arthroplasty (commonly known as a knee replacement or TKA), the damaged surfaces of the thighbone, shinbone and sometimes the kneecap are replaced with artificial components. Patellar resurfacing is the additional step of replacing the underside of the kneecap with a small plastic button, so it glides smoothly against the new metallic groove of the femoral component.
Surgeons who favour resurfacing argue it reduces the risk of anterior knee pain (pain at the front of the knee) and lowers the chance of needing further surgery. Those who prefer to leave the patella untouched point to the potential complications of adding another implant, including fracture risk, loosening or patellar clunk syndrome (a catching sensation caused by scar tissue). This is precisely the question the study set out to answer, using a single implant model to eliminate design-related bias.
All 6,078 knees in the analysis received the same SCORE prosthesis (Amplitude, Valence, France), a posterior-stabilised, rotating-bearing implant specifically designed with a 6-degree patellar groove and a constant radius of curvature to distribute pressure evenly across the kneecap’s track. This so-called “patella-friendly” design aims to reduce patellar complications whether or not the kneecap is resurfaced.
Revision rates with or without patellar resurfacing: what the data shows
The primary finding of the study is striking. At five years of follow-up, the revision rate (the proportion of patients requiring a second surgery to change any component) was identical in both groups: 98.4% survival in patients whose patella was resurfaced and 98.4% in those whose patella was left intact (p = 0.95). In other words, resurfacing the kneecap did not reduce the overall likelihood of needing further surgery.
When reoperation of any kind was considered (not only implant revision but any new procedure on the same knee), the results were equally comparable: 96.0% survival in both groups (p = 0.83).
| Outcome at 5 years | No resurfacing (n = 3,415) | Resurfacing (n = 2,663) | p value |
| Implant revision-free survival | 98.4% | 98.4% | 0.95 |
| Reoperation-free survival | 96.0% | 96.0% | 0.83 |
| Patella-related revision-free survival | 99.3% | 99.7% | 0.02 |
A nuance emerged when only patella-specific complications were isolated. The non-resurfaced group had a slightly higher rate of patella-related revisions (0.7% versus 0.3%, p = 0.02). However, this small difference did not translate into a higher overall revision or reoperation rate, suggesting it was offset by other types of complications in the resurfaced group. Importantly, the Cox regression model confirmed that factors such as age, sex, BMI, surgical approach, use of cement and navigation did not significantly alter these findings.
Anterior knee pain after TKA and functional outcomes
Anterior knee pain after TKA is one of the most frequently cited reasons for resurfacing the patella. This study assessed functional outcomes in 1,641 patients who reached at least five years of follow-up.
The KSS score (Knee Society Score, a widely used measure of knee function combining a clinical and a functional component) showed no meaningful difference between the two groups: 181.7 in the resurfaced group versus 179.9 in the non-resurfaced group (p = 0.51).
Knee flexion (how far the knee can bend) was statistically better in the resurfaced group: 118.8 degrees versus 116.1 degrees (p = 0.03). However, this 2.7-degree difference falls well below the minimal clinically important difference, which ranges from 3.8 to 8.8 degrees depending on the assessment tool. In practice, this means the difference would be undetectable by most patients in daily life.
These results align with previous randomised controlled trials that found patients were generally unable to perceive a difference between their resurfaced and non-resurfaced knee when both sides were operated in the same session.
Does the patella-friendly implant design change the equation?
The concept of the patella-friendly implant for total knee arthroplasty was developed to optimise kneecap tracking regardless of whether resurfacing is performed. The SCORE prosthesis used in this study features a patellar groove with a consistent depth and a constant curvature, designed to maintain even contact pressure as the knee bends and extends.
This study’s results suggest that when such a design is used, the decision to resurface becomes less consequential. The overall revision rate remains the same either way, and functional scores are comparable. This is consistent with a meta-analysis by Simpson et al. (2023), which found no clinically significant advantage to resurfacing when a modern patella-friendly design was employed.
However, research by Kuo et al. (2020) has shown that even specifically designed implants do not always perfectly restore the native anatomy of the patellofemoral compartment. This can lead to understuffing of the patellar groove, which may weaken the extensor mechanism (the muscles and tendons that straighten the knee). Newer alignment philosophies, such as kinematic alignment, may help address this by better restoring native patellar tracking.
The study does have limitations. As a retrospective database analysis, a significant number of patients were lost to follow-up before the five-year mark. The two groups were not randomised, leading to baseline differences in age, gender and surgical technique. These factors were accounted for in the statistical model and did not change the conclusions, but future prospective trials on a single implant design would further strengthen the evidence.
Conclusion & Findings
This large-scale study confirms that systematic patellar resurfacing during total knee arthroplasty using a patella-friendly implant does not reduce the overall revision rate nor improve functional scores at five years. While non-resurfaced knees showed a marginally higher rate of patella-specific complications, this did not affect the broader picture. These findings support a personalised, case-by-case approach to patellar management rather than a one-size-fits-all strategy.
For those interested in exploring more of the scientific research conducted by Professor Cavaignac, his body of work covers a wide range of topics in knee surgery and orthopaedics, each contributing to a better understanding of how surgical decisions impact patient outcomes.
If you are considering knee replacement surgery or seeking a specialist opinion, Professor Etienne Cavaignac brings the kind of rigorous, evidence-based approach that allows patients to make informed decisions with confidence.