A partial knee replacement and a total knee replacement are different operations for different patterns of arthritis. A quote for one can't be compared with a quote for the other until you know which one fits your knee, and what happens if the plan changes once the surgeon is in the operating room. These are the questions to settle first.
What "partial" actually replaces
The knee has three compartments: the medial (inner side), the lateral (outer side) and the patellofemoral (front of the knee, between the kneecap and the thighbone). A partial, or unicompartmental, knee replacement resurfaces only the damaged compartment with metal and plastic components, and leaves the rest of the knee alone (AAOS OrthoInfo, 2026).
In a total knee replacement, metal components resurface the ends of the thighbone and shinbone, a plastic spacer sits between them, and the kneecap may or may not be resurfaced with a plastic button (AAOS OrthoInfo, 2026). The implant options for that operation are covered in the knee implant types guide.
Who may be suitable for a partial
According to OrthoInfo, the arthritis has to be limited to one compartment. Where you feel the pain gives a clue:
- Pain almost entirely on the inner or outer side of the knee suggests a possible partial.
- Pain across the whole knee points towards a total.
- Pain under the kneecap points towards a patellofemoral replacement.
OrthoInfo adds that you may not be suitable if you have inflammatory arthritis, significant knee stiffness or ligament damage. X-rays show how far the arthritis has spread, and the examination checks movement and stability. Neither is something a quote form can assess.
If you're told you're "borderline" for a partial, ask which finding makes it borderline: the spread of arthritis on the X-rays, the stability of the ligaments, or stiffness. Ask too whether the final decision will only be made in the operating room. The answer tells you how seriously to take the conversion questions further down.
How the decision is made in clinic
The choice rests on three things together. Your history: where the pain is, what makes it worse, and which non-surgical treatments have failed. Your examination: how far the knee bends and straightens, whether it's stable, and whether the ligaments seem intact. Your X-rays: how far the arthritis and any deformity extend. A surgeon who recommends one operation over the other should be able to point to findings in all three. If the explanation rests only on "it's quicker" or "it's more reliable", ask what in your own knee makes that true.
What the largest UK trial found
The TOPKAT trial randomised 528 people with arthritis limited to the medial compartment to either a partial or a total knee replacement, across 27 UK sites, and followed them for five years. The results below are as summarised by NIHR Evidence (Beard et al., Lancet, 2019):
- Function and pain: on the 48-point Oxford Knee Score, the total group improved by 18 points and the partial group by 19, a difference the trial didn't consider clinically meaningful.
- Hospital stay: an average of 4.3 days for a total and 3.2 days for a partial.
- Further surgery: re-operations in 8% of the total group and 6% of the partial group. Revisions in 4% of each.
- Cost to the NHS: partial replacement was more cost-effective over five years.
The caveats matter. Long-term revision rates are still uncertain, 44 patients ended up having the operation they weren't assigned to, and the results assume surgeons experienced in partial replacement. The summary also notes that fewer than 9% of UK knee replacements were partials at the time.
Trade-offs in plain terms
| Factor | Partial knee | Total knee |
|---|---|---|
| What's preserved | Healthy bone, cartilage and ligaments in the other compartments | All three compartments are resurfaced |
| Early recovery | OrthoInfo describes a quicker recovery, less pain and less blood loss, with most patients back to daily activities by six weeks | OrthoInfo describes most people resuming normal daily activities within three to six weeks |
| Feel | Many patients say it feels more natural | Varies |
| Future surgery | A total may be needed later if arthritis develops in another compartment | Revision possible if the implant wears or loosens |
| Durability data | OrthoInfo reports "excellent" medium- and long-term survivorship in appropriate candidates, without giving a figure | OrthoInfo reports more than 90% still functioning well at 15 years |
The recovery rows come from different OrthoInfo pages, not from a head-to-head comparison, so read them as general patterns rather than a promise for either operation.
What recovery looks like after each
After a partial knee replacement, OrthoInfo describes little or no time in hospital, putting weight on the leg straight after surgery, and using a walker, cane or crutches for the first several days or weeks. A physical therapist works on range of motion and strength, and antibiotics are often continued for about 24 hours. Most patients can return to their usual daily activities by six weeks.
After a total knee replacement, OrthoInfo says physical therapy begins within hours of surgery. Most patients stay overnight, some stay longer, and same-day discharge is possible if it's planned with the surgeon. Help is typically needed for several weeks with cooking, shopping, bathing and laundry, and most people resume driving about four to six weeks after surgery. Either way, your own timeline is set by your team. The recovery timeline guide compares the joints more broadly.
The switch in the operating room
OrthoInfo explains that during a planned partial, the surgeon checks all three compartments and the ligaments. If partial replacement turns out to be inappropriate, they may do a total instead, and this backup should be discussed beforehand. In TOPKAT, intra-operative findings, such as more widespread arthritis than expected, were among the reasons some patients crossed over.
For anyone comparing quotes, especially across borders, this is where most of the financial uncertainty sits. Ask:
- Based on my images, how likely is it that you'd switch to a total once you're inside?
- If you switch, what changes in the implant, the hospital stay and the rehab plan?
- What would the price be if the operation changes, and is that in writing?
- Will the consent form cover both operations?
Questions that belong before the price
- Which compartment or compartments do you see as affected, and on which images?
- Are my ligaments intact, and how did you assess them?
- Why this operation for me rather than the other one?
- How many partial knee replacements do you do? (TOPKAT's results assumed experienced surgeons.)
- If I have a partial now and arthritis spreads later, what does converting to a total involve?
- What results should I realistically expect for the activities I care about?
Use the checklist below to track which of these you've had answered. Tick a line only when you have a clear answer, ideally in writing.
Why the price comes last
A partial knee quote can look cheaper simply because it describes a smaller operation. That only helps you if the smaller operation is right for your knee, and if the quote also states what you'd pay if it became a total on the day. Once the operation is agreed, line the quotes up using the quote packet, so the implant, stay and rehab assumptions match.
What a usable quote should state
- The operation by name: medial, lateral or patellofemoral partial, or total.
- Whether the price changes if a planned partial becomes a total, and by how much.
- The implant assumptions for both cases.
- The expected hospital stay, and what an extra night costs.
- What rehabilitation is included and what you arrange yourself.
Frequently asked questions
Is partial knee replacement better for younger patients?
OrthoInfo reports good medium- and long-term results for modern partial implants in both younger and older patients, when they're used in appropriate candidates. Suitability depends on the pattern of arthritis, not on age alone.
Can a partial be converted to a total later?
Yes. OrthoInfo notes that a total knee replacement may be needed later if arthritis develops in the parts of the knee that weren't replaced.
Does a partial last as long as a total?
The sources read here don't give a like-for-like long-term figure. OrthoInfo reports more than 90% of total knees working well at 15 years. In TOPKAT, revision rates at five years were 4% in both groups, and longer-term results were still pending.
What is a patellofemoral replacement?
It's a partial replacement of the compartment behind the kneecap. OrthoInfo links it with pain felt mainly under the kneecap, when the other compartments are healthy.
Why might two surgeons recommend different operations?
They may read the images differently, examine the ligaments differently, or have different experience with partial replacement. A focused second opinion can bring out which of these is driving the difference.
Compare a joint replacement plan or quote
Start with the joint, side, destination preference and timing. You do not need to upload the full medical record here.
Related joint-replacement guides
Orthopedic lead network
- AAOS OrthoInfo — Unicompartmental (Partial) Knee Replacement (2026)
- AAOS OrthoInfo — Total Knee Replacement (2026)
- NIHR Evidence — summary of the TOPKAT trial (Beard et al., Lancet, 2019)
These sources support general education about joint replacement and medical travel. They do not establish a personal diagnosis, treatment recommendation, implant choice or travel-clearance date.