A partial knee replacement replaces only the worn part of the knee. A total knee replacement replaces the whole joint surface.
- Pain relief is much the same with both.
- A partial usually means a shorter hospital stay and a quicker recovery.
- Complications are less common after a partial.
- A partial is more likely to need redoing later.
- Only about 1 in 4 people are suitable for a partial.
The right choice depends on where the arthritis is in your knee.
Partial vs Total Knee Replacement at a Glance
| Topic | Partial knee replacement | Total knee replacement |
|---|---|---|
| Who it suits | Arthritis in one part of the knee | Arthritis in one part or several |
| The cut | Smaller | Longer, down the front of the knee |
| Time in hospital | Often home the same day or next morning | Usually 1 to 3 nights |
| Driving | About 4 to 6 weeks | About 6 weeks |
| Pain relief | Much the same | Much the same |
| Complications | Serious problems uncommon. Fewer problems overall. | Serious problems uncommon. More problems overall. |
| Still working at 15 years | About 3 in 4 (about 9 in 10 at 10 years) | More than 9 in 10 |
What Is the Difference?
Your knee has three parts. These are the inner side, the outer side, and the part behind the kneecap. Arthritis often starts in just one of them. Most often it is the inner side.
A partial knee replacement resurfaces only the worn part. The healthy parts and the ligaments are left alone. You may also hear it called a half knee replacement or a unicompartmental knee replacement. The Oxford knee is one well-known type.
A total knee replacement resurfaces the whole joint. The ends of the thigh bone and shin bone are capped with metal. A plastic spacer sits between them. The back of the kneecap may be resurfaced too.
There is a third option. If the arthritis is only behind the kneecap, that part alone can be replaced. This is called a patellofemoral replacement.
You can read more about how a partial knee replacement is done. You can also read what a total knee replacement involves.
Am I Suitable for a Partial Knee Replacement?
A partial only works if the rest of the knee is healthy. You are more likely to be suitable if:
- the arthritis is in one part of the knee only
- that part is worn right through, often called bone on bone
- the main ligaments in your knee are sound
- your knee still bends and straightens well
- your leg is not badly bowed or knock-kneed
- you do not have an inflammatory arthritis, such as rheumatoid arthritis
Previous knee surgery or injury can change the advice.
Roughly 1 in 4 people who need a knee replacement are suitable for a partial. NICE writes the guidance for the NHS. It says people with arthritis on the inner side only should be offered the choice.[3]
If the arthritis is in more than one part of the knee, a total is usually the better operation. X-rays taken while you stand show which parts are worn.
Sometimes the surgeon finds more wear during the operation. A total is then done instead, as agreed with you beforehand.
Age alone does not decide it. In UK records, the typical age is 64 for a partial and 70 for a total.[4] Both are done in younger and older people.
How Does Recovery Compare?
Recovery is usually quicker after a partial. The operation is smaller and less bone is removed.
- In hospital. Many people go home the same day or the next morning after a partial. After a total, most people stay 1 to 3 nights.
- Driving. Most people drive again about 4 to 6 weeks after a partial. After a total, it is about 6 weeks.
- Work. Desk work is often possible 2 to 4 weeks after a partial. After a total, allow 4 to 6 weeks.
A large UK trial found the same pattern. People who had a partial left hospital about a day sooner.[1]
Older people, or those who live alone, may need a longer stay. Both operations need the same commitment to your exercises afterwards.
How Does the Knee Feel Afterwards?
For people who could have either, pain relief is much the same. The main UK trial is called TOPKAT. It gave 528 people one operation or the other. There was no real difference in their pain and function scores at 5 years.[1] That was still true at 10 years.[2]
Some people say a partial feels more like their own knee. This may be because the ligaments and healthy parts are kept.
At 5 years, 91 in 100 people with a partial said they would have the operation again. For a total, it was 84 in 100.[1]
Neither operation is a guarantee. In the trial, about 8 in 10 people were satisfied with either one.
Which Is Safer?
Serious problems are uncommon with both operations. Problems of any kind are less common after a partial.
In the UK trial, 20 in 100 people had a complication of some kind within 5 years of a partial. After a total, it was 27 in 100.[1]
Large studies of hospital records point the same way. They show fewer blood clots, heart problems and strokes after a partial.[5] People who have a partial are often younger and fitter, which explains part of this.
Which Lasts Longer?
A total knee replacement is less likely to need redoing. This is the main point in its favour.
- About 9 in 10 partial knee replacements are still working well at 10 years.
- In long-term records from Finland, about 3 in 4 partials were still working at 15 years.[6]
- More than 9 in 10 total knee replacements are still working at 15 years.[6]
Why the gap? After a partial, arthritis can later develop in the parts of the knee that were left. The implant can also work loose. A partial is simpler to redo than a total. So surgeons may be more willing to redo one that still hurts.
In the TOPKAT trial the gap was small. At 10 years, about 6 in 100 partials and 4 in 100 totals had been redone.[2]
The people in the trial were carefully chosen, and their surgeons were experienced. Both of those things matter. In everyday records, the gap is wider.[5]
What Does the Evidence Favour?
NICE says people who are suitable should be offered the choice.[3] The TOPKAT researchers went a step further. After 5 years, they said a partial should be the first choice for people who are suitable.[1] At 10 years, they reported similar results and similar redo rates for both.[2]
That advice only applies if a partial suits your knee. It also assumes a surgeon who does partials regularly.
Can a Partial Be Changed to a Total Later?
Yes. If arthritis spreads to the rest of the knee, a partial can be changed to a total knee replacement. This is a bigger operation than a first knee replacement, but it is a well-established one. Results are usually good, but on average not as good as a first-time total.
You can read more about revision knee replacement surgery.
Does It Matter How Often Your Surgeon Does Partials?
Yes. Results are better when a surgeon does partial knee replacements regularly.
One large UK study looked at this. Results were acceptable when partials made up at least 1 in 5 of a surgeon's knee replacements. They were best when partials made up about half. They were poorer when a surgeon did very few.[7]
It is reasonable to ask your surgeon how many they do. You can also look up your surgeon on the National Joint Registry website. Our guide explains how to read a surgeon's NJR results.
Where Does Robotic Surgery Fit?
Both operations can be done with or without robotic help. The robot does not do the operation. It helps the surgeon place the implant more closely to the plan. This matters in a partial knee, where a small error in position can shorten its life.
The evidence is still building. One UK trial compared robotic and standard partial knee replacement. People rated their knees the same at 5 years. Fewer in the robotic group needed more surgery. It was a small trial, and the two groups had different implants, so the result needs confirming.[8]
For total knee replacement, a large UK trial found no difference in results at one year.[9] Mr Hussain is trained on three robotic systems: MAKO, ROSA and CORI.
Our guide compares robotic and conventional knee replacement.
Questions to Ask Your Surgeon
- Which parts of my knee are worn?
- Am I suitable for a partial? If not, why not?
- How many partial and total knee replacements do you do each year?
- What do your results look like on the National Joint Registry?
- What would recovery look like for me?
- What happens if a partial needs changing later?
What Should You Do Next?
The first step is an up-to-date assessment, with X-rays taken while you stand. Mr Shakir Hussain performs both partial and total knee replacement in Birmingham. That means the advice is not tied to one operation.
Our main guide covers knee replacement surgery in Birmingham. You can also arrange a private knee consultation in Birmingham.
Frequently Asked Questions
Is a half knee replacement the same as a partial knee replacement?
Yes. Half knee replacement, partial knee replacement and unicompartmental knee replacement all mean the same operation. Only the worn part of the knee is replaced.
Is recovery quicker after a partial knee replacement?
Usually, yes. Many people go home the same day or the next morning. Most drive again in about 4 to 6 weeks. After a total knee replacement, most people stay 1 to 3 nights and drive at about 6 weeks.
How long does a partial knee replacement last?
About 9 in 10 partial knee replacements are still working well at 10 years. At 15 years, about 3 in 4 are still working. A total knee replacement is less likely to need redoing.
Can a partial knee replacement be changed to a total later?
Yes. If arthritis develops in the rest of the knee, a partial can be changed to a total knee replacement. It is a bigger operation than a first knee replacement.
Am I too old or too young for a partial knee replacement?
Age alone does not decide it. What matters is where the arthritis is in your knee. In UK records, the typical age is 64 for a partial and 70 for a total.
Which is better, a partial or a total knee replacement?
Neither is better for everyone. If your arthritis is in one part of the knee, a partial offers a quicker recovery and fewer complications. A total is less likely to need redoing. If the arthritis is in more than one part, a total is usually the right operation.
References
- Beard DJ, Davies LJ, Cook JA, et al; TOPKAT Study Group. The clinical and cost-effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT): 5-year outcomes of a randomised controlled trial. Lancet. 2019;394(10200):746-756. Full text
- Assessing clinical and cost effectiveness of total versus partial knee replacement (TOPKAT): 10-year follow-up of a multicentre, randomised controlled trial. Lancet Rheumatol. 2026;8(2):e116-e126. Full text
- National Institute for Health and Care Excellence. Joint replacement (primary): hip, knee and shoulder. NICE guideline NG157, recommendation 1.7.1.
- National Joint Registry (NJR). 23rd Annual Report 2026: knee replacement.
- Wilson HA, Middleton R, Abram SGF, et al. Patient relevant outcomes of unicompartmental versus total knee replacement: systematic review and meta-analysis. BMJ. 2019;364:l352. Full text
- Evans JT, Walker RW, Evans JP, et al. How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up. Lancet. 2019;393(10172):655-663. Full text
- Liddle AD, Pandit H, Judge A, Murray DW. Optimal usage of unicompartmental knee arthroplasty: a study of 41,986 cases from the National Joint Registry for England and Wales. Bone Joint J. 2015;97-B(11):1506-1511. Full text
- Banger M, Doonan J, Rowe P, et al. Robotic arm-assisted versus conventional medial unicompartmental knee arthroplasty: five-year clinical outcomes of a randomized controlled trial. Bone Joint J. 2021;103-B(6):1088-1095. Full text
- Robotic-arm-assisted versus conventional total knee replacement (RACER-Knee): a pragmatic, multicentre, participant-masked and assessor-masked, superiority, randomised controlled trial. Lancet. 2026. Full text
This page is for general information and is not a substitute for a consultation. Which operation suits your knee is assessed individually.
Mr Shakir Hussain
Consultant Hip and Knee Surgeon at the Royal Orthopaedic Hospital Birmingham, with over 5,000 procedures and certification on all three major robotic knee platforms: MAKO, ROSA, and CORI.