Arthritis of the Knee | Action Medical Research | Children's Charity | Children's Charity

Arthritis of the knee: comparing total and partial knee replacement

First published on 30 October 2008

Updated on 3 March 2014

What did the project achieve?

A trial comparing total and partial knee replacement has provided new evidence that will enable thousands of people with arthritis to make a more informed decision about which type of surgery is best for them.

“Over 70,000 knee replacement operations are performed every year in the UK,” says Mr Matt Costa, the surgeon who led this research at Warwick Medical School.1-3 “Over 10 per cent of those who undergo surgery have arthritis that’s limited to the area behind the knee-cap. For these people, a lack of evidence has meant it’s long been unclear whether it’s better to replace the whole knee or just the area behind the knee-cap.”

“Our study of 64 patients suggests that both types of knee replacement provide excellent results in terms of pain relief and improved function,” continues Mr Costa. “When talking to their doctor about which type of surgery seems best for them, people can now feel more confident that total and partial knee both offer good outcomes. In this study, we followed patients for a year after surgery and we now are hoping to perform larger trials with longer follow-up to find out which type of knee replacement lasts better.”

This research was completed on 30 April 2013

Over 50,000 people with severe arthritis undergo knee replacement surgery each year in the UK.1,2,3 Most have a total knee replacement. However, around 10% of those who undergo surgery have arthritis that affects only the area around the knee-cap.4 For these people, it’s unclear whether it’s best to replace the whole knee or just the area around the knee-cap. Researchers are investigating which type of surgery is best in a clinical trial.

What's the problem and who does it affect?

Unclear evidence

Every year in the UK, over 50,000 people have such bad arthritis in their knee that they choose to undergo knee replacement surgery.1.2.3

Around 5,000 of those who undergo surgery have arthritis that is limited to the area around the knee-cap.1,2,3,4 They suffer pain in the knee that gets worse with any movement. Activities like climbing stairs or standing up from a chair can be excruciatingly painful. This can be extremely frustrating, limiting day-to-day activities and participation in sports, and sometimes forcing people to give up work.

Knee replacement surgery can free people from pain, meaning they can become much more active again. Most people have the whole knee joint replaced, even if their arthritis is limited to the area around the knee-cap.

However, it is possible to replace just the area around the knee-cap. Early trials of this technique gave unsatisfactory results, but more recent improvements mean it is now unclear which type of surgery is best. The lack of evidence means choosing between total and partial knee replacement presents a very real conundrum for surgeons and their patients.

What is the project trying to achieve?

Clinical trial

Around 60 people with arthritis in the area around the knee-cap are taking part in a clinical trial. They are being randomly allocated to two treatment groups: half are having a total knee replacement (which is known as total knee arthroplasty) and the other half are having just the area around the knee-cap replaced (which is called patellofemoral arthroplasty).

Researchers are assessing the volunteers before surgery and at four time points over the following year. They are comparing the pros and cons of each type of surgery – assessing effects on knee function, quality of life, levels of disability and physical activity, and any complications.

To avoid bias in the assessments, neither the volunteers, nor the researcher who’s assessing them will know which type of surgery each person has had.

What are the researchers' credentials?

Project LeaderMr M Costa PhD
Project team
  • Dr Juul Achten MSc PhD
  • Mr Nick Parson BSc MSc PhD
  • Professor Damian Griffin MA MPhil FRCS
  • Mr Tim Spalding MBBS FRCS
LocationWarwich Medical School, University of Warwick, University Hospitals Coventry and Warwickshire NHS Trust
Other locations
  • University Hospital at Walsgrave, Coventry
Duration3 years
Grant awarded30 October 2008
Start date1 May 2009
End date30 April 2013
Grant amount£91,470.00
Grant codeAP1170,GN1737

We do not provide medical advice. If you would like more information about a condition or would like to talk to someone about your health, contact NHS Choices or speak to your GP. Please see our useful links page for some links to health information, organisations we are working with and other useful organisations. We hope you will find these useful. We are not responsible for the content of any of these sites.

The project leader, Mr Matt Costa, is an experienced surgeon and researcher based at Warwick Orthopaedics. The unit is rapidly developing an international reputation as a centre of excellence for both surgery and research in three important fields: joint replacement surgery, treating sports injuries and surgery for traumatic injuries. A large number of the unit’s experienced surgeons will be involved in this study.

The unit’s research focus is on clinical trials of new and innovative interventions – investigating different approaches to joint replacement surgery and to healing fractured or ruptured bones and tendons.

Who stands to benefit from this research and how?

More informed decision making

This research will benefit people who need surgery to treat severe arthritis that is limited to the area around their knee-cap, and that does not affect the rest of their knee joint – that’s 5,000 people every year in the UK.1,2,3,4

The researchers aim to determine which type of surgery seems best – replacing the whole knee joint or just the area around the knee cap. They hope to give sufferers and their surgeons high-quality evidence on the relative benefits of the two treatments, so that everyone is in a better position to choose the best type of surgery for them.

Replacing the whole knee joint is currently the gold standard. However, in theory, replacing just the area around the knee-cap might have important benefits. It preserves more of the person’s own knee joint – preserving bone, ligaments and so on – and it is less invasive, meaning recovery ought to be quicker. Results of this study will provide objective evidence to help prove or disprove this theory.


  1. National Joint Registry for England and Wales. 5th Annual Report.
  2. National Joint Registry for England and Wales. 4th Annual Report.
  3. National Joint Registry for England and Wales. 3rd Annual Report.
  4. Davies AP, Vince AS, Shepstone L, Donell ST, Glasgow MM. The radiologic prevalence of patellofemoral osteoarthritis. Clin Orthop Relat Res 2002; 402:206-12.
Help us spread the word