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What is a Partial Knee Replacement?

The knee is divided into 3 compartments - the medial, lateral, and patellofemoral compartments. A partial knee replacement is a surgical procedure used to treat patient with moderate-to-severe osteoarthritis (OA) isolated to only 1 or 2 compartments of the knee. With partial knee replacements, only the damaged compartments of the knee are replaced, and the healthy compartments are preserved.


A partial knee replacement is designed to resurface the end of the bone and preserve as much bone stock for any future conversions that may be needed. It is expected to last between 10-15 years and would allow an easier conversion to a primary total knee replacement, if needed.


Compared to a total knee replacement, patients who undergo partial knee replacement surgery typically have a quicker and less painful recovery. Additionally, a partial knee replacement removes less bone and preserves all the ligaments of the knee. This gives the knee a more natural feel.


This handout is intended to describe a single compartment replacement (unicompartmental medial or lateral replacement) and 2 compartment replacement (bicompartmental).

Who is a candidate for a Partial Knee Replacement?

Patients who are candidates for a unicompartmental replacement have moderate-to-severe osteoarthritis of only 1 compartment of the knee, either the medial or lateral weightbearing compartment. Often, the pain is isolated to that single arthritic compartment. Whereas patients who are candidates for a bicompartmental replacement have moderate-to-severe osteoarthritis of 2 compartments of knee – the patellofemoral compartment (kneecap and groove) and either the medial or lateral weightbearing compartment. In these patients, the remaining compartment of their knee is healthy. In addition to radiographic findings of osteoarthritis, these patients have failed conservative/non-operative treatments. Conservative treatments include weight loss, physical therapy, braces, ambulatory aids, anti-inflammatory oral medications, and injection treatments (cortisone, hyaluronic acid, etc.).


To determine if you are a candidate for a partial knee replacement, your surgeon will first obtain plain x-rays to assess areas of bone-on-bone arthritis. Typically, your surgeon will also have you get an MRI of your knee to evaluate all other compartments of your knee and confirm the most suitable type of partial knee replacement. It is critical that the other compartment(s) of your knee that is/are not to be replaced have normal, healthy cartilage. Otherwise, you may not experience significant improvement following surgery and require further surgery. 


The goal of a partial knee replacement is to restore your ability to perform everyday activities, such as stair climbing, walking on uneven ground, getting out of a low chair or car, or sitting with the knees bent for a prolonged period of time. These activities are generally difficult to perform when there is osteoarthritis present in the knee.


This procedure will help patients feel very comfortable and pain-free, but it is not intended for return to high-level impact loading, twisting activities. Premature failure of the components by wear is likely in patients who resume running and pivoting sports. The prosthesis is designed to restore quality of life with activities of daily living.

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