Partial knee replacement surgery replaces one part of a damaged knee with an artificial joint. Compared with total knee replacement, partial knee replacement is less painful and has a shorter recovery time, but it is not suitable for everyone.

Partial knee replacement surgery is an alternative to total knee replacement for some people with knee osteoarthritis (OA). It is less invasive than total knee replacement and can help relieve pain and restore function to the knee joint.

Partial knee replacement is also known as unicompartmental knee replacement, unicondylar knee arthroplasty (UKA), and partial knee resurfacing surgery.

This article discusses the purpose, procedure, and risks of partial knee replacement surgery.

Learn about the stages of knee OA.

A surgeon and a person holding their knee after partial knee replacement surgery.Share on Pinterest
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The purpose of partial knee surgery is to relieve pain and improve function in the knee. It can also help improve the knee’s alignment and reduce inflammation. Doctors typically use partial knee surgery to treat OA.

Not all people with OA are candidates for partial knee surgery. This surgery is only appropriate for people who have damaged one part of their knee joint, usually the medial — inner — compartment.

The knee comprises three major compartments:

  • medial compartment — the inner part
  • lateral compartment — the outer part
  • patellofemoral compartment — behind the kneecap

Doctors may recommend partial knee replacement for people who:

  • have OA limited to one compartment of the knee
  • have a good range of motion in their knee
  • have no symptoms of inflammatory arthritis

The specific criteria for partial knee replacement therapy may vary depending on the person’s circumstances. Doctors may also consider a person’s pain levels, impact on daily activities, and expectations for surgery outcomes.

Read about tricompartmental OA.

Compared with total knee replacement, partial knee replacement offers the following advantages:

  • less invasive
  • shorter recovery time
  • less pain and blood loss
  • smaller risk of infection
  • preserves more of the natural knee structure

However, partial knee replacement surgery is not suitable for everyone. For example, people with arthritis in multiple compartments of the knee may require total knee replacement instead.

Other disadvantages of partial knee replacement, when compared with total knee replacement, include:

  • It may not be as durable.
  • It does not always provide complete pain relief. For example, it does not address patellofemoral OA, which involves pain behind the kneecap.
  • It may require revision surgery in the future, which can be technically challenging and lead to a poorer outcome than having a total knee replacement originally.

Before surgery begins, the patient will undergo a thorough medical and physical examination to determine if they are a suitable candidate for partial knee replacement. This may involve imaging tests, such as X-rays or MRIs, to assess the condition of the knee joint and determine if a partial knee replacement is appropriate.

The patient should stop taking certain medications, such as blood thinners, to reduce the risk of complications during surgery.

Once cleared for surgery, the doctor will provide preoperative instructions, such as not eating or drinking the night before the procedure and arranging transportation to and from the hospital.

Immediately before the procedure, the patient will receive anesthesia, and the surgeon will mark the knee with a marker to verify the surgical site.

Partial knee replacement surgery can last 1–2 hours.

The surgeon makes a small incision in the front of the knee and examines the three compartments of the knee joint. If the damage is limited to one compartment, the surgeon removes the damaged cartilage and bone and replaces it with an artificial implant.

The surgeon positions and secures the implant and then closes the incision with stitches or staples.

If the surgeon finds more extensive damage than expected, they may perform a total knee replacement. However, they will discuss this possibility with the person before the operation.

After surgery, the person will go to a recovery room for monitoring. They will be able to leave the hospital later the same day or the following day, depending on their condition.

Recovery times vary, but most people can return to their regular daily activities within 6 weeks. Swelling and pain are normal and may last up to 6 months.

Doctors may recommend physical therapy to help with recovery and prevent complications.

Learn what to expect from knee surgery rehabilitation.

Partial knee replacement surgery is an effective treatment option for some people with knee osteoarthritis. According to one 2020 study, most people notice improvements in function, pain, and stiffness within 6 months of surgery.

Around 70% of partial knee replacements last 25 years.

Partial knee replacement surgery has a lower complication rate than total knee replacement.

Potential complications of partial knee replacement include:

Partial knee replacement is a surgical procedure that replaces one part of the knee joint with an artificial implant. Doctors recommend partial knee replacement for osteoarthritis in one part of the knee, such as the medial or lateral compartments.

People who have inflammatory arthritis or arthritis in multiple compartments of the knee are not candidates for partial knee replacement.

Most people notice an improvement in symptoms within 6 months of surgery.