Most knee arthritis does not affect the whole joint. It concentrates in one compartment, usually the inner side, while the rest of the knee stays healthy. Replacing the entire joint in that situation removes a great deal of cartilage that was working perfectly well, and partial knee replacement exists precisely to avoid that.

Partial knee replacement rewards patient selection more than almost any procedure in knee surgery, and Steven Struhl, MD has practiced in New York since 1991. He is board certified in orthopedic surgery and separately in sports medicine, is a Fellow of the American Academy of Orthopaedic Surgeons, performs robotic assisted partial knee replacement, and operates at NYU Langone Orthopedic Hospital.

What Partial Knee Replacement Replaces

The knee has three compartments, the inner, the outer, and the one behind the kneecap. Unicondylar replacement resurfaces one of them and leaves the others alone, along with both cruciate ligaments and the healthy cartilage everywhere else.

The procedure has been performed since the early 1970s with mixed early results. Implant design, instrumentation, and surgical technique have improved markedly over the last twenty five years, and current results bear little resemblance to that early record.

Who Is a Candidate for Partial Knee Replacement

Selection is the single largest factor in how well this operation does, which is why the criteria are specific rather than general.

Who Is Not a Candidate

Advantages and Trade Offs of Partial Knee Replacement

This is the honest comparison, and it runs in both directions.

Partial Knee Replacement Surgery and Recovery

Surgery is performed under spinal or general anesthesia and takes approximately two hours, since a smaller exposure demands more precision rather than less. The bone surfaces are prepared with a saw or a burr, trial components are placed and the knee taken through motion, and the femoral and tibial components are then seated with or without cement. A drain is usually placed.

Infection rates are approximately one percent, and the bearing surface generally lasts ten to fifteen years before wear becomes a consideration.

What Happens If a Partial Knee Replacement Fails

This is one of the genuine advantages of the procedure and it deserves stating plainly. If a partial replacement fails, or if arthritis progresses into the other compartments years later, it can be revised to a total knee replacement without difficulty, because relatively little bone was removed at the first operation. That option is a substantial part of why partial replacement makes sense for a patient who is younger than the usual replacement candidate and who meets the criteria.

Frequently Asked Questions About Partial Knee Replacement

How do I know whether I need a partial or a total knee replacement?

It comes down to how much of the joint is involved. Partial replacement suits arthritis confined to one compartment, usually the inner side, with the other compartments still healthy on imaging and on examination. Arthritis in more than one compartment, significant angular deformity, inflammatory arthritis such as rheumatoid disease, an unstable knee, and previous osteotomy all point toward total knee replacement. Standing radiographs generally answer the question, and the joint is confirmed directly during surgery.

Does a partial knee replacement feel more natural than a total?

Most patients report that it does. Partial replacement preserves both cruciate ligaments and the healthy compartments, and those structures carry the position sense that makes a knee feel like your own. Patients frequently describe better motion and a more natural sensation than after total replacement. The trade is that partial replacement is not quite as reliable at eliminating all pain, since the arthritis in the untreated compartments, however mild, is still there.

Can a partial knee replacement be converted to a total later?

Yes, and this is one of the genuine advantages of the procedure. If a partial replacement fails or if arthritis progresses into the other compartments years later, it can be revised to a total knee replacement without difficulty, because relatively little bone was removed at the first operation. That option is a meaningful part of why partial replacement makes sense for younger patients who meet the criteria.

How much smaller is the surgery?

The incision runs around seven centimeters compared with the considerably longer approach for total replacement, and less bone is removed. In practice that means a shorter hospital stay, a quicker recovery, less physical therapy, and a transfusion being rarely required. Surgery time is comparable, around two hours, since the smaller exposure demands more precision rather than less.

How long does a partial knee replacement last?

The bearing surface generally lasts ten to fifteen years, comparable to total replacement, and long term survival figures for partial replacement are somewhat lower than for total replacement. Implant design, instrumentation, and technique have improved markedly over the past twenty five years, and results now are considerably better than the mixed record of the 1970s that gave the procedure its early reputation. Patient selection remains the largest single factor in how well it does.

Does robotic assistance change partial knee replacement?

It changes the accuracy of the implant position, which matters more in partial replacement than in total, because a partial implant sits alongside your own cartilage and has to match it closely. Robotic assisted partial knee resurfacing uses a CT based plan and a constrained cutting boundary to place the components within the plan. The operation and the recovery are otherwise the partial knee replacement described on this page.

Schedule a Partial Knee Consultation in New York City

Whether a partial replacement suits your knee is answered by standing radiographs and an examination rather than by how much pain you are in, since two knees that hurt the same amount can need very different operations. Dr. Struhl evaluates knee arthritis and partial knee candidates at his Manhattan and White Plains offices. Contact Shoulders & Knees to schedule a consultation.