What is a partial knee replacement?

Partial knee replacement, also called unicompartmental knee arthroplasty (UKA), is surgery that may be used to treat severe knee arthritis that effects only one part of the knee. A knee surgeon may recommend knee joint replacement if someone has:

  • symptoms of knee arthritis, including knee pain and stiffness that keeps them up at night or prevents them from doing daily activities
  • knee pain that continues despite other treatments

Knee replacement surgery aims to reduce pain and restore function.

Total knee replacement is when the whole knee is replaced. This is for people with osteoarthritis affecting the whole knee. Some people with osteoarthritis that is limited to just one part (compartment) of the knee may be eligible for unicompartmental or ‘partial’ knee replacement.

In a partial knee replacement, only the damaged compartment is replaced, with a new metal and plastic surface. The healthy cartilage and bone in the rest of the knee is left alone. Usually partial knee replacements use implants placed between the end of the thigh bone and the top of the shin bone. Some types of partial knee replacements can also replace the part of the joint under the kneecap.

A doctor explains what partial knee replacement involves and shows what the implants look like.

Partial knee replacement surgery involves a smaller incision (surgery cut) than traditional total knee replacement surgery. Many studies have shown that partial knee replacement works very well in most people who are suitable for it. The advantages of this type of surgery over total knee replacement include less blood loss during surgery, less pain after surgery, and a quicker recovery.

Because the bone, cartilage, and ligaments in the healthy parts of the knee are kept, most people say that a partial knee replacement feels more ‘natural’ than a total knee replacement, and it usually bends much better.

A doctor talks about the advantages of partial knee replacement.

The potential disadvantages of partial knee replacement compared with total knee replacement include slightly less predictable pain relief, and the possible need for more surgery. For example, a total knee replacement may be necessary in the future if arthritis develops in the parts of the knee that have not been replaced.

A partial knee replacement operation usually lasts between 1 and 2 hours. As with any kind of surgery, there are risks involved. Although rare, the most common risks include blood clots, infection, injury to the nerves or vessels, continued pain, as well as the risks of carried by anaesthetics.

A doctor talks about the risks of partial knee replacement surgery.

Because a partial knee replacement is done through a smaller, less invasive cut, the time spent in hospital is shorter, and recovery and return to normal activities is faster than with a total knee replacement.

A doctor talks about recovering from partial knee replacement surgery.

People who have a partial knee replacement usually have less pain after surgery, less swelling, and have easier rehabilitation than people having total knee replacement. In most cases, they go home 1 to 3 days after the operation. They can usually resume their regular daily activities 6 weeks after surgery.

See our resources section for more information.

Bone surgery

We interviewed 33 people about their experiences of two common orthopaedic operations: partial knee replacement surgery and  subacromial decompression shoulder surgery, also known as keyhole...