Partial knee replacement: what it is, who it suits and how long recovery takes

The knee moves smoothly because the ends of the bones are covered with a layer of tough tissue called cartilage. The NHS explains that if cartilage is worn away by osteoarthritis or damaged by an injury, the bones rub against each other and the joint becomes painful and stiff. In a knee replacement, the damaged parts are replaced with metal and plastic parts.

In a partial knee replacement, only the bones on the affected side of the knee are replaced. The NHS says this is used when you have arthritis in one half of your knee. A total knee replacement, by contrast, replaces the lower end of the thigh bone and the upper end of the shin bone, and is the most common type of knee replacement.

The NHS says a knee replacement may be recommended if knee pain is having a big effect on your life and alternatives to a knee replacement have not worked. Most people who have a knee replacement have pain and movement problems caused by osteoarthritis. Other causes, such as rheumatoid arthritis or arthritis following an injury, are less common.

Which type of operation you have depends on things like how damaged your knee is, your age and your general health, according to the NHS. A partial replacement is an option only when arthritis is limited to one half of the knee. Your orthopaedic surgeon will decide, using an examination and scans, whether this applies to you.

The two operations use the same general approach. The table sets out the differences the NHS describes. The NHS pages do not compare long-term results between the two, so that choice is one to discuss with your surgeon.

The NHS says you usually go into hospital on the day of the operation. You have either a general anaesthetic, where you are asleep, or a local anaesthetic in the spine, where you are awake but have no feeling from the waist down. The operation usually takes about 1 to 2 hours.

In outline, the surgeon removes the damaged surfaces and fits new parts over the ends of the bones, then closes the cut with stitches or clips and covers it with a dressing. Afterwards you stay in a recovery room until you are fully awake, and may be given medicines for pain.

You will be asked whether you consent to your details being added to the National Joint Registry, which the NHS says collects and monitors details of knee replacements to help improve patient safety, experience and outcomes.

The NHS says it may take several months or longer to fully recover from a knee replacement, depending on your age and general health, and that recovery from a partial knee replacement should be shorter than from a total one. Nurses and physiotherapists help you start walking soon after the operation, and you will need crutches or a walking frame at first.

You can usually go home if there are no signs of complications and you can get around safely using crutches. The NHS says this is usually 1 to 4 days after the operation. Before you leave you will usually be given compression stockings to help prevent blood clots, and a physiotherapist or occupational therapist will talk to you about daily activities and home exercises.

It is important to follow the advice the hospital gives you. The NHS says following the exercises early in your recovery helps with long-term strength and movement in the knee.

• Use crutches or a walking stick at first, then try walking without an aid after about 6 weeks if you feel ready.

• Wear your compression stockings at all times, taking them off only to wash them. Most people need to wear them for at least 6 weeks.

• Do the exercises your physiotherapist recommends, and keep your leg raised as much as possible to reduce swelling.

• Avoid twisting your knee, bending down and reaching up as much as you can.

• Do not sit with your legs crossed for the first 6 weeks, and do not sleep with a pillow under your knee.

• Do not kneel on your new knee until your doctor says you can, and avoid standing for long periods.

The NHS describes a knee replacement as a common and safe procedure but notes that, as with any operation, there are risks. Most people have no complications, and when there are any they are usually minor and treatable. The risk depends on your age and general health.

• Blood clots or deep vein thrombosis (DVT). This is often not serious, but a clot in the leg can sometimes travel to the lungs. Compression stockings or blood-thinning medicines may be suggested.

• Wound infection. There is a small chance of this, usually treated with antibiotics. If it spreads deep into the knee joint, further surgery may be needed.

• Damage to a blood vessel, nerve or ligament around the knee. This is not common and can be repaired during surgery or will heal afterwards.

• Ongoing problems with the new knee, such as difficulty bending, pain and stiffness, or the knee feeling unstable when you stand or walk. Physiotherapy and exercises may help.

Ask for an urgent GP appointment or get help from NHS 111 if you have recently had a knee replacement and you have throbbing or cramping pain in your leg, a high temperature or you feel hot, cold or shivery, oozing or pus from the wound, or redness, tenderness, swelling or pain in the knee that is not getting better or is getting worse. The NHS says these could be signs of an infection or a blood clot.

Call 999 or go to A&E if you have pain and swelling in your leg together with difficulty breathing or chest pain. The NHS says this could be a blood clot in the lungs, which needs to be treated immediately.

The NHS says knee replacements are usually very successful and result in no pain in the knee and better movement. Most people find their daily life improves. Most knee replacements last for about 25 years, and depending on when the operation was done you may need another replacement later in life, but this is not common.

The NHS pages read for this guide do not give separate lifespan figures for partial and total replacements, so ask your surgeon how your age, activity level and the type of implant may affect the outlook for you.

On the NHS, planned knee surgery follows assessment by your GP and an orthopaedic team, after alternatives to a knee replacement have been tried, which the NHS gives as the condition for recommending the operation. Waiting times for planned surgery vary by area and are worth asking about at your appointment.

Some people choose private surgery to shorten the wait or to choose their surgeon and hospital. The operation and recovery plan are broadly similar either way. Whichever route you use, it is reasonable to ask your surgeon how often they perform partial replacements, what follow-up is included, and what happens if a complication arises.