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Treatments
A bone and ligament preserving operation that resurfaces only the worn part of the knee, for arthritis affecting a single compartment. It often offers a quicker recovery and a more natural-feeling knee.
about this treatment
A partial knee replacement, also called a unicompartmental or half knee replacement, resurfaces only the worn part of the knee rather than the whole joint. The knee has three compartments, the medial (inner), the lateral (outer) and the kneecap, and when arthritis affects just one of them, often the medial side, only that compartment needs to be replaced.
Because Mr Oni removes less bone and keeps your healthy cartilage and ligaments, including the cruciate ligaments, a partial replacement preserves more of the natural feel and movement of the knee and usually allows a quicker recovery than a total knee replacement.
Robotic assistance can be used where appropriate and is discussed at your consultation. This can allow controlled, precise bone removal and is particularly valuable in partial knee replacement.
A partial replacement is only suitable when the other compartments and the ligaments are still healthy. If arthritis later develops elsewhere in the knee, a partial replacement can be converted to a total knee replacement. Mr Oni will examine your knee and review your X-rays to advise whether a partial or total replacement is right for you.
is this right for me?
Surgery is never the automatic answer. Mr Oni recommends a partial knee replacement only when arthritis is confined to one compartment of the knee, the other compartments and ligaments are healthy, and conservative treatments are no longer controlling the pain.
X-rays confirm arthritis in just one part of the knee, usually the medial (inner) compartment, with the rest of the joint and the ligaments still healthy.
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Physiotherapy, weight management, injections including Arthrosamid, and pain relief are no longer giving adequate relief.
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Knee pain is affecting your sleep, walking, work, or the activities you value such as golf and gardening.
Not sure if you qualify?
Many patients come to Mr Oni uncertain whether their symptoms are "bad enough" for treatment. The answer always comes from a proper clinical assessment - not from a website. Book a consultation and Mr Oni will give you an honest view.
outcomes
These are the benefits and outcomes typically expected from this treatment. Realistic expectations matter, so you go into any treatment fully informed.
Less bone is removed and the ligaments are preserved, so recovery is usually faster than after a total knee replacement, with most patients back to normal activities in about six weeks.
By keeping your healthy bone, cartilage and ligaments, a partial replacement preserves more of your natural knee movement than a total replacement.
A smaller incision and less surgery mean less pain afterwards, less blood loss, and often a shorter hospital stay.
Mr Oni plans the procedure with robotic assistance, which is especially valuable in partial knee replacement for accurate, controlled placement of the implant.
Recovery after a partial knee replacement is usually quicker than after a total knee replacement, because less bone is removed and the ligaments are preserved. The timeline below is a general guide, and Mr Oni will give you a realistic, personalised expectation at your consultation.
Physiotherapy begins. You will stand and walk short distances, often without a frame, with pain managed by medication.
Walking with a stick and then unaided, and managing stairs. Many patients can drive an automatic car from around six weeks, sometimes sooner.
Most patients return to normal daily activities and office work within about six weeks.
Continued improvement in strength and confidence, with a return to golf and other valued activities. Most patient will peak in their recovery journey at about a year
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Robotic-assisted knee replacement, planned and performed around your exact anatomy for greater precision.
The cost depends on the hospital and whether you are self-funding or using private medical insurance. Mr Oni's team can provide a clear, itemised quote at your consultation.
Recovery is usually quicker than after a total knee replacement. Most patients are walking the same day, driving an automatic at around four to six weeks, and back to normal daily activities within about six weeks, with continued improvement over the following months with recovery peaking at around one year.
A partial knee replacement is only suitable when arthritis affects a single compartment. If arthritis later develops in another part of the knee, a further operation to convert it to a total knee replacement may be needed. Mr Oni will advise whether it is the right choice for your knee.
Neither is simply better. When only one compartment is worn, a partial replacement preserves more of the natural knee and allows a quicker recovery. When arthritis is more widespread, a total knee replacement is more reliable. Mr Oni recommends whichever suits your knee.
Modern partial knee implants are designed to last many years. If it does wear out, or arthritis spreads to another compartment, it can be revised to a total knee replacement.
Most patients return to driving at around six weeks, sometimes sooner. This is confirmed with you at your follow-up appointment.
Answers written by Mr Tofunmi Oni, Consultant Orthopaedic Surgeon (MBChB BSc PGDip FRCS (Tr & Orth), GMC 7074916), who performs partial and total knee replacement at The Horder Centre in Crowborough and Nuffield Health Tunbridge Wells. Figures come from the National Joint Registry, NICE, the TOPKAT trial and the sources listed at the end. Last reviewed October 2026.
A partial (unicompartmental) knee replacement resurfaces only the worn compartment of the knee, usually the inner (medial) side, through a smaller incision and with a quicker recovery than a total knee replacement. NICE recommends offering a choice of partial or total replacement to people with arthritis confined to the medial compartment. To be suitable you need intact ligaments, particularly the anterior cruciate ligament, and arthritis limited to one compartment on examination and imaging. Partial knees made up a record 14.7% of UK knee replacements in 2024, and partial knee patients are typically five to six years younger than total knee patients.
People with arthritis across more than one compartment, inflammatory arthritis such as rheumatoid, a deficient or absent anterior cruciate ligament, a fixed deformity that cannot be corrected, or significant stiffness. Age on its own is not a bar; Versus Arthritis notes a partial knee can be considered at any age.
The main one is a higher revision rate in registry data: about 77% of partial knees survive 15 years compared with 93% of total knees, and roughly one in ten needs further surgery by ten years, partly because arthritis can progress in the rest of the knee and partly because surgeons revise a partial more readily. The best performing designs show about 5% revision at ten years in the NJR. Results depend heavily on the surgeon: an analysis of 41,986 NJR cases found that surgeons using partial knees for fewer than 5% of their cases had the highest revision rates, with the best results when partials made up 40% to 60% of a surgeon's knee practice.
For the right knee, the evidence says it is at least as good and recovers faster. In the TOPKAT randomised trial of 528 patients, partial and total replacement gave the same improvement in knee score at five years, the same 4% revision rate, slightly fewer reoperations with partial (6% against 8%), and partial was cheaper and gave more quality adjusted life years. Registry data show higher long term revision for partials overall, which is why patient selection and surgeon experience matter so much. NICE says either is reasonable for isolated medial compartment arthritis and the choice should be shared with you.
Registry pooled data show about 77% surviving at 15 years, 72% at 20 and 70% at 25, against 93%, 90% and 82% for total knees. The NJR reports the best brands with revision rates of 1.9% at five years and 5% at ten. When a partial knee does fail, it can usually be converted to a total knee replacement, which is generally a more straightforward operation than revising a total knee.
Recovery after a partial is generally quicker and less painful, because less bone is removed, the ligaments are preserved and the incision is smaller. The NHS describes recovery as typically quicker after a partial, and the driving advice reflects it: about three weeks after a partial compared with six after a total. At five years in the TOPKAT trial the knee scores were the same for both operations.
Most people are walking unaided within a few weeks, driving at around three weeks, back to a desk job within a few weeks and to a physical job in six to twelve weeks. Swelling can take three months to settle and the knee keeps improving for up to a year. Golf, cycling and swimming are usually back by about three months.
The same guidance as for a total knee: low impact sport is encouraged, contact sport and repetitive high impact loading are generally advised against, and kneeling is fine once the wound has healed. Because the ligaments are preserved, a partial knee usually feels more natural than a total, which is one of its main attractions.
There is no best age. It is chosen on the pattern of arthritis and the state of the ligaments, not on age. Younger patients have a higher lifetime chance of revision whichever operation they have, and a partial knee's easier conversion to a total is sometimes an argument in its favour in younger people, while its higher registry revision rate is sometimes an argument against. That is a conversation to have with your surgeon, with your X rays in front of you.
National Joint Registry, 22nd Annual Report 2025, executive summary and knee chapter. https://reports.njrcentre.org.uk
NICE NG157, Joint replacement (primary): hip, knee and shoulder (June 2020), recommendation 1.7.1. https://www.nice.org.uk/guidance/ng157
Beard DJ et al. The clinical and cost effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT). Lancet 2019;394:746-56. https://doi.org/10.1016/S0140-6736(19)31281-4
Evans JT et al. How long does a knee replacement last? Lancet 2019;393:655-63.
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. Bone Joint J 2015;97-B:1506-11.
NHS.uk, Knee replacement: what happens and recovery (reviewed September 2026). https://www.nhs.uk/conditions/knee-replacement/
Versus Arthritis, Knee replacement surgery. https://www.versusarthritis.org/about-arthritis/treatments/surgery/knee-replacement-surgery/
Mr Oni consults and operates at several leading private hospitals across the region, so you can choose the location most convenient for you.
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