Patellar Resurfacing During Knee Replacement

Key Points

During total knee replacement, the surgeon may replace the joint surface on the back of the kneecap with a polyethylene component or retain the patient’s natural patellar surface.
Average pain, function and satisfaction are often similar with either approach, although some evidence suggests resurfacing reduces anterior knee pain and the need for further surgery.
Resurfacing introduces its own uncommon risks, including fracture, component loosening, overstuffing and problems with kneecap tracking.
NICE currently recommends offering patellar resurfacing to people undergoing primary elective total knee replacement.[1]
Practice still varies, but patients should be informed of the national recommendation, the alternatives and the surgeon’s usual practice.

What Is the Patella?

The patella, or kneecap, is part of the knee joint. Its cartilage-covered undersurface glides within a groove at the front of the femur as the knee bends and straightens.

During total knee replacement, the worn surfaces of the femur and tibia are replaced. The surgeon must also decide how to manage the patella.

The principal options are:

patellar resurfacing, in which a measured layer of cartilage and bone is removed and replaced with a polyethylene button, usually secured with bone cement; or
patellar retention, in which the natural patellar surface is not replaced.

If the patella is retained, it is not necessarily left completely untouched. Depending on the surgeon’s technique, prominent osteophytes may be removed and the shape or tissues around the patella may be addressed. The retained surface then moves against the metal trochlear groove of the femoral component.

The Case for Resurfacing

The main argument for resurfacing is that it removes the arthritic joint surface from the back of the kneecap.

Potential advantages include:

a lower risk of pain arising from continuing patellofemoral arthritis;
a reduced likelihood of needing a later operation involving the patella;
more predictable movement against the femoral component in some implant designs; and
possible long-term cost-effectiveness through fewer readmissions or subsequent procedures.

Some meta-analyses of randomised trials report lower rates of anterior knee pain and revision or reoperation after resurfacing.[2] However, improvements in general knee scores and satisfaction are usually small or inconsistent.

The Case for Retaining the Patella

Retaining the natural patellar surface avoids removing additional bone and avoids complications specifically associated with a patellar component.

Potential advantages include:

preservation of the patient’s patellar bone;
avoidance of component loosening or wear;
no risk of an incorrectly positioned patellar button;
reduced risk of making the reconstructed patella too thick or too thin; and
preservation of future surgical options.

An unresurfaced patella can nevertheless remain painful. Anterior knee pain after replacement is not always caused by the patellar surface: implant rotation, instability, soft-tissue irritation, referred pain, infection and other conditions can produce similar symptoms.

Risks Specific to Resurfacing

Patellar resurfacing is well established, but it is not risk-free. Recognised complications include:

fracture of the remaining patellar bone;
loosening or wear of the polyethylene component;
malposition or altered tracking of the kneecap;
excessive removal of bone;
making the reconstructed patella too thick, known as overstuffing;
disruption of the blood supply to the patella; and
injury to the extensor mechanism.

These complications are uncommon when appropriate bone thickness is preserved and the component is positioned carefully. Their consequences can nevertheless be significant if they occur.

What Does NICE Recommend?

NICE guideline NG157 states that patellar resurfacing should be offered to people undergoing primary elective total knee replacement.[1]

When developing this recommendation, NICE found insufficient clinical evidence to conclude that resurfacing, non-resurfacing or selective resurfacing produced clearly superior clinical outcomes. Its recommendation was influenced substantially by economic evidence suggesting that routine resurfacing was cost-effective over ten years because of reduced hospital readmissions.

“Offer” does not mean that every patella must be resurfaced regardless of the circumstances or the patient’s informed preferences. It does mean that resurfacing should be presented as an available option and that any recommendation not to resurface should be explained in the context of the evidence and the individual patient.

NICE has also identified selective resurfacing—deciding according to individual clinical or operative findings—as an area requiring further research.

What Does the Long-Term UK Trial Show?

The Knee Arthroplasty Trial, or KAT, was a large UK multicentre randomised trial involving 1,715 patients.

Its recently published 20-year results found no statistically significant difference in the main Oxford Knee Score or the other principal clinical outcomes. However, the results generally favoured resurfacing, and the resurfacing group accumulated more quality-adjusted life-years without greater overall healthcare costs. The investigators concluded that the evidence was weighted towards resurfacing as the first-choice approach.[3]

This does not demonstrate that every individual patient will benefit from resurfacing. It does, however, mean the evidence can no longer be summarised simply as perfectly balanced or directionless.

Secondary Patellar Resurfacing

If an unresurfaced patella is thought to be causing persistent pain, a later operation can be performed to add a patellar component. This is known as secondary patellar resurfacing.

It is important not to present this as a guaranteed solution. Anterior knee pain after knee replacement has several possible causes, and identifying the patella as the true source can be difficult.

A systematic review of 604 secondary resurfacing procedures found improvement in patient-reported outcomes in approximately 53% of cases and satisfaction in approximately 59%. Around 10% underwent a further revision procedure, although the underlying studies were retrospective and varied considerably.[4]

Careful investigation of infection, component position, instability, loosening and referred pain is therefore required before secondary resurfacing is considered.

My Usual Practice

My usual practice is not to resurface the patella routinely. In my own patient series, I have not so far needed to perform a secondary patellar resurfacing.

This is a description of my personal clinical experience rather than evidence that secondary resurfacing will never be required or that non-resurfacing is the best policy for every patient. The significance of any individual surgeon’s experience also depends on the number of patients treated and the duration and completeness of follow-up.

Current NICE guidance recommends offering resurfacing, and this national recommendation should form part of the discussion. The final plan should take account of the condition and thickness of the patella, the proposed implant, the potential benefits and risks of each option, the surgeon’s experience and the patient’s informed preference.

What This Means for You

It is reasonable to ask your surgeon:

Do you routinely resurface the patella, never resurface it or decide selectively?
What is the reason for your usual practice?
What does NICE currently recommend?
Is there anything about my kneecap that favours one option?
Which femoral implant design will be used?
What are the risks of resurfacing in my particular case?
What would happen if the patella were retained and I later developed anterior knee pain?

Different surgeons may reach different recommendations, but the decision should not be portrayed as arbitrary. It should be based on the available evidence, national guidance, the proposed implant, individual operative findings and an informed discussion with the patient.

In More Depth

The findings of individual trials and meta-analyses do not agree completely. Some large trials find similar average pain and functional scores, while pooled analyses report reductions in anterior knee pain and reoperation with resurfacing.[2,3]

Results may also be influenced by:

the design of the femoral component;
the quality and shape of the patella;
component rotation and overall alignment;
patellar thickness and tracking;
whether osteophytes or surrounding nerves are addressed when the patella is retained; and
how anterior knee pain and reoperation are defined.

Patellar resurfacing is therefore not an isolated decision. It forms part of the broader task of reconstructing a stable knee with appropriate alignment, soft-tissue balance and smooth patellar tracking.

This article provides general information and does not replace individual clinical advice. Patellar management should be discussed with your surgeon as part of the consent process for total knee replacement.

References

National Institute for Health and Care Excellence. Joint replacement (primary): hip, knee and shoulder. NICE guideline NG157, recommendation 1.7.2. Updated 2025. NICE recommendations.
Tang X, He Y, Pu S, et al. Patellar resurfacing in primary total knee arthroplasty: a meta-analysis and trial sequential analysis of 50 randomized controlled trials. Orthop Surg. 2023;15(2):379–399. doi: 10.1111/os.13392.
Murray DW, Hudson J, Dakin H, et al. Patellar resurfacing in total knee replacement: 20-year clinical and economic results of a large multicentre, randomised controlled trial in the UK. Lancet. 2026;408(10549):52–61. doi: 10.1016/S0140-6736(26)00652-5.
Andronic O, Suravaram V, Lu V, et al. What are the outcomes of secondary patella resurfacing for dissatisfaction following primary knee arthroplasty? A systematic review and meta-analysis of 604 knees. J Arthroplasty. 2024;39(4):1093–1107.e1. doi: 10.1016/j.arth.2023.10.027.

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