If arthritis has worn out your knee, do you need the whole joint replaced or only part of it? The knee has three compartments: inner (medial), outer (lateral) and the one behind the kneecap. A partial, or unicompartmental, replacement resurfaces just one of them and keeps your ligaments and the healthy cartilage. A total replacement resurfaces all of the joint surfaces.
A partial replacement is a smaller operation with a quicker recovery and a more natural-feeling knee, but only a minority of patients have the right pattern of wear for it, and it is somewhat more likely to need a further operation later. A total replacement is the more versatile and durable solution. Your X-rays, ligaments and examination, not your preference alone, decide which is on the table.
Key points
- A partial replacement only works when arthritis is confined to one compartment and the ligaments, especially the ACL, are intact.
- Partial replacements typically mean less pain, a shorter hospital stay, better bend and a more natural feel.
- Total replacements have a lower revision rate over time and treat arthritis throughout the knee.
- Surgeon volume matters greatly for partial replacements. Results are better with surgeons who do them regularly.
- Rehabilitation lasts months. If you travel for surgery, physiotherapy at home must be arranged before you leave.
Who is a candidate for a partial replacement
The classic candidate has bone-on-bone arthritis on the inner side of the knee, pain that they can point to with one finger on that side, and a knee that is otherwise in good working order. Studies suggest that perhaps a quarter to a half of people needing a knee replacement could meet the criteria, though in practice far fewer receive one. Age and weight are no longer regarded as strict exclusions, but very high BMI and very high activity demands call for caution.
- Arthritis limited to one compartment, with preserved cartilage in the others on X-ray or MRI
- An intact and functioning anterior cruciate ligament and stable collateral ligaments
- A deformity that is mild and correctable, generally less than about 10 to 15 degrees of bow
- A good range of motion, with the knee straightening to within about 10 to 15 degrees and bending beyond 100 degrees
- No inflammatory arthritis such as rheumatoid disease, which affects the whole joint
Who is better served by a total replacement
A total replacement suits arthritis in two or three compartments, inflammatory arthritis, significant deformity or stiffness, ligament deficiency, and widespread pain that you cannot localise. It also suits people who want to minimise the chance of a second operation, particularly in older age when further surgery is less welcome.
Its downsides are a larger operation with more blood loss, a longer and more painful early recovery, and a knee that many people describe as good but not quite natural. Surveys consistently find that around 1 in 5 to 1 in 10 patients are not fully satisfied after a total knee replacement, often because of persistent pain or stiffness without a clear cause. Realistic expectations, set before surgery, are one of the best predictors of satisfaction.
Side by side comparison
The figures below are typical ranges drawn from mainstream practice and joint registries in general terms. Individual results vary with your health, your surgeon and how hard you work at rehabilitation.
- Hospital stay: Partial: 1 to 2 nights, sometimes day surgery. Total: 2 to 4 nights.
- Walking aids: Partial: often 1 to 3 weeks. Total: typically 4 to 6 weeks.
- Driving: Partial: commonly around 3 to 4 weeks. Total: around 6 weeks. Only when you can brake hard and are off strong painkillers.
- Feel and movement: Partial: more natural, better bend, easier kneeling for some. Total: reliable pain relief, kneeling often uncomfortable.
- Serious complications: Lower with partial: less bleeding, fewer clots, infections and medical complications.
- Durability: Both commonly last 15 to 20 years or more. Partial replacements have a higher revision rate, partly because arthritis can progress in the untouched compartments.
- If it fails: A partial can usually be converted to a total. Revising a total is a bigger undertaking.
Why surgeon experience matters more for partial knees
Registry data from several countries show that revision rates for partial replacements fall markedly when the surgeon performs them often, and rise when they are an occasional operation. Positioning tolerances are tight and patient selection is a skill in itself. Ask how many partial replacements your surgeon performs per year and what proportion of their knee replacements are partial. A proportion around 20 percent or more suggests a surgeon who is comfortable with the indication.
Robotic or computer-assisted systems can improve the precision of implant alignment for both operations. Better alignment on X-ray has not yet translated into clearly better long-term function or survival in the evidence, so treat it as a useful tool rather than a reason in itself to choose a provider.
Recovery timeline
You will stand and walk with support on the day of surgery or the next day. Swelling, warmth and night pain are normal for weeks. The timeline below is typical for a total replacement, with a partial generally running 2 to 4 weeks ahead. Your surgeon's and physiotherapist's instructions override it.
- Days 1 to 3: Walking with a frame or crutches, bending and straightening exercises, ice and elevation, clot prevention started.
- Weeks 1 to 2: Stairs with a rail, wound check, staples or stitches out at around 10 to 14 days. Aim to straighten fully and bend to about 90 degrees.
- Weeks 3 to 6: Progress from two crutches to one to none. Bend improving towards 110 to 120 degrees. Daily exercises.
- Weeks 6 to 12: Driving, longer walks, stationary cycling, return to desk work and then lighter manual work.
- Months 3 to 12: Strength and stamina keep improving. Swelling after activity can persist for 6 to 12 months.
Travelling for a knee replacement: the honest picture
Plan to stay about 10 to 14 days so the wound is checked and you are safe on stairs before flying. Knee replacement carries a meaningful risk of blood clots for several weeks, and a long flight adds to it. Expect blood thinning medication, usually for 2 to 5 weeks, and ask for an aisle seat, extra legroom and airport assistance. Many surgeons prefer you to delay long-haul flights longer where possible.
The larger issue is what happens afterwards. Supervised physiotherapy in the first 6 to 12 weeks strongly influences your final range of motion, and stiffness that is not addressed early may need a manipulation under anaesthetic. Deep infection, although uncommon at around 1 to 2 percent, can appear weeks or months later and needs prompt orthopaedic care locally. Before booking, make sure a physiotherapist and a doctor at home are ready to take over, and bring home your operative note, implant labels and X-rays.
Have you tried enough before surgery
Joint replacement is for persistent pain and loss of function that has not responded to a proper trial of non-surgical care, together with X-ray evidence of advanced arthritis. That care includes a structured strengthening programme, weight loss where relevant, walking aids, simple painkillers or anti-inflammatories if safe for you, and sometimes a steroid injection for flare-ups. Evidence for hyaluronic acid and PRP injections is mixed, and neither regrows cartilage. If an injection is given, surgeons usually wait about 3 months before replacing the joint, because of infection risk.
Keyhole washout of an arthritic knee does not help and is no longer recommended. In younger patients with a bowed leg and arthritis on one side only, a realignment osteotomy is another alternative worth asking about.
When to get medical help
Seek emergency care for chest pain, breathlessness or coughing blood, or for a calf that becomes painful, hot and swollen, as these suggest a blood clot. Contact your surgical team the same day if the wound leaks after the first few days, becomes increasingly red, hot or painful, or if you develop fever or chills. A knee that suddenly swells and hurts months or years later, especially after dental work or another infection, needs urgent orthopaedic assessment for joint infection.
This guide is general information and does not replace advice from the doctor treating you. If you would like a specialist to look at your own case, send your reports and photographs: a Clinic-Y coordinator replies within 24 hours, and the case review is free.
Frequently Asked Questions
Can I kneel after knee replacement?
It does not harm the implant, but many people find it uncomfortable because of the scar and numb skin at the front. Kneeling tends to be easier after a partial replacement. A padded surface and gradual practice from about 3 months help.
Which sports are realistic afterwards?
Walking, swimming, cycling, golf, doubles tennis and gentle hiking are widely encouraged. Running, jumping and contact sports are generally discouraged because they may speed up wear and loosening, although some people with partial replacements return to more.
Should I have both knees replaced at once?
It means one anaesthetic and one rehabilitation, but the operation is longer and carries higher risks of clots, heart strain and transfusion. It is usually reserved for healthy patients under about 70 with severe disease in both knees. Staging the knees a few months apart is the more cautious route.
Will the implant set off airport security?
It often does. Tell the officer you have a joint replacement. Implant cards are generally not required or accepted as proof, and a brief hand search or scanner check is routine.