What is a unicompartmental arthroplasty?

Unicompartmental arthroplasty is also called a partial knee replacement. It is a surgical procedure that replaces only a portion of the knee that is affected by knee osteoarthritis. Unicompartmental arthroplasty is used to relieve the symptoms of arthritis when occurring in just one compartment of the knee. In a “normal” arthroplasty, or a total knee replacement, the damaged bone and cartilage is resurfaced and replaced with metal and plastic components. In a unicompartmental knee replacement only a portion of the knee is resurfaced and replaced. Not everyone needs a total knee replacement, and a few select patients are excellent candidates for unicompartmental arthroplasty. If you would like to be evaluated for the best type of knee replacement for your knee condition, we can help! Our “best in class” surgical experts, through our telemedicine platform, can diagnose your knee condition and offer personalized surgical options for the best possible outcome.

Who should have a partial knee replacement?

The choice between a partial knee replacement or complete knee replacement depends primarily on the condition of the knee joint. The knee has three main compartments where osteoarthritis may be present; these are called the medial, lateral and patellofemoral compartments. The medial compartment refers to the inside of the joint, toward the center of the body. The lateral compartment refers to the outside of the joint. The patellofemoral compartment is the area between the kneecap and the femur (thigh bone). Osteoarthritis can form in any of these compartments but is more frequently found in the medial portion of the knee. Partial knee replacement is an alternative treatment for a total knee replacement in patients who have osteoarthritis in one compartment of the knee. Patients who have osteoarthritis in two or more of the compartments are better candidates for a total knee replacement.

How is unicompartmental arthroplasty, or partial knee replacement surgery performed?

The surgical procedure for a unicompartmental arthroplasty is very similar to a total knee arthroplasty. The goal is also similar: replace the damaged portion of the knee with new, synthetic components. The surgery is done in the following steps:

  • Patient is placed under anesthesia, either general or regional.
  • The surgeon makes a small incision over the knee.
  • The entire knee is examined for damage and the surgeon removes the damaged bone and tissue.
  • A pre-sized prosthetic component is placed over the repaired portions of the knee and secured with bone cement.
  • A spacer is inserted between the two metal components to create a smooth gliding surface.
  • The surgeon checks the components for correct motion of the knee.
  • The knee is sutured closed.

What are the advantages and disadvantages of a unicompartmental arthroplasty?


  • Quicker recovery with less pain
  • Less blood loss
  • Many patients are able to walk without a cane or walker earlier than a total knee replacement.
  • The return to “normal” activities is less limited. Patients are able to continue with activities that have lower impact like swimming, tennis, golf and biking.


  • Knee osteoarthritis can still develop in the other compartments of the knee, prompting additional surgery.
  • Slightly less predictable pain relief

How long will a unicompartmental arthroplasty last?

When done properly and in patients who meet the criteria for unicompartmental arthroplasty, the long-term outcome is good. Studies show the majority (90%) of partial knee replacements last 10 years or longer. Patient enjoy the same durability as a total knee replacement with the benefit of quicker recovery and the sensation of a “normal” knee, rather than a replacement.

How long is the recovery after a partial knee replacement?

The recovery after a unicompartmental arthroplasty is quicker than a complete knee replacement recovery. Physician post-operative protocols should be followed carefully for the best possible outcome. In general, healthy, active patients undergoing a partial knee replacement can often resume regular activity in about 6 to 8 weeks.

For more information on unicompartmental arthroplasty or a partial knee replacement, or to find out if you are a candidate for this specialized surgical procedure and to receive a second opinion for your knee condition, please contact our experts, by clicking on “Connect With a Doctor.” You will be connected to one of our orthopedic telemedicine experts through our state-of-the-art telemedicine platform.