What is partial knee replacement surgery?

Partial knee replacement, also known as unicompartmental knee arthroplasty, is the replacement of only one of the three compartments of the knee.

This is an alternative to total knee replacement, as damage is limited to only part or one side of the knee. It is done through a smaller incision and the recovery time is generally shorter in comparison to a total knee replacement.


A partial knee replacement is often recommended when there is only a minor deformity in the knee or arthritis is contained to one side of the joint.

If the arthritis has extended to other areas, the condition may be deemed “severe” and may require a total knee replacement.

The surgery

Prior to surgery, your surgeon and anaesthetist will discuss your options for anaesthesia.

The surgeon will make an incision at the knee, then explore the three compartments to verify that the problem is in fact limited to only one compartment and that ligaments are intact. Once assessment is complete, the damaged bone and tissue are removed and replaced with plastic and metal prosthetics and attached with bone cement. The incisions are then closed.

If there is more damage than initially expected, a total knee replacement may be performed. This will be discussed as a possibility prior to the operation.

Risks and complications

Potential risks from this surgery include fluid build-up around the knee joint, potential failure of the replacement parts and pain with kneeling after recovery. Blood clots and infections are also possible.

As partial knee replacements only focus on one contained area of the knee, there may be potential for more surgery in the future if arthritis develops in the parts that have not been replaced. This procedure allows the option for a total knee replacement to be performed in the future, if needed.

Preparation and recovery

Before your operation, a ‘prehab’ exercise program may be prescribed to you by your physiotherapist and you are encouraged to start a regular exercise activity. At this time, your physiotherapist will ideally explain what exercises you will need to do post-surgery.

Post-surgery, you may need to stay in hospital for one to two days, although most people are able to be discharged and go home on the day of surgery.

You should be able to place your full weight on to the knee right away, although you may need the assistance of crutches for walking. Most patients are able to walk without assistance within three to four weeks after the surgery. Physiotherapy is required for four to six months.