Overview
The knee has three compartments — medial, lateral, and patellofemoral. When arthritis affects only one, resurfacing the entire joint may be overkill. Partial knee replacement targets just the worn compartment and preserves the ACL, PCL, menisci, and healthy cartilage of the other two compartments. Patients often describe the result as feeling more like their own knee.
How the Procedure Works
We resurface only the worn compartment — typically the medial femoral condyle and its matching tibial plateau — with a smaller metal-and-polyethylene implant. Both cruciate ligaments, the opposite compartment, and the patellofemoral joint are left entirely untouched. Patient selection is the most important factor in outcomes: the ACL must be functional (it drives the knee's natural rollback kinematics that a partial replacement relies on), the deformity must be passively correctable, and the other compartments must have intact cartilage. Implant sizing and tibial slope are set intraoperatively to match the native knee — the goal is a component that participates in normal knee motion rather than constraining it. The preserved ligament proprioception is why patients often describe partial replacement as feeling more like their own knee than a total replacement does.
When to Consider Partial Knee Replacement
Partial knee replacement is generally offered when symptoms, imaging, and a trial of non-operative care together point to surgery as the next step. The typical picture includes:
Single-compartment arthritis
Cartilage loss isolated to the medial or lateral compartment, confirmed on weight-bearing X-rays.
Intact ligaments
A functional ACL and PCL — the ligaments must still stabilize the knee for a partial replacement to work.
Correctable deformity
A varus or valgus deformity that reduces passively, suggesting the other compartments are still healthy.
Conditions This Treats
Physicians Who Perform Partial Knee Replacement
Providers Who Surgically Assist with Partial Knee Replacement
Risks & Why We Still Recommend It
Every operation carries risk. The reason we offer this procedure is that the condition, left untreated, causes daily pain localized to one compartment and progressive loss of the active, low-intensity life those patients typically want back. That is the trade we are managing — not eliminating risk, but choosing the smaller of two unfavorable trajectories.
The risks we discuss with patients before partial knee replacement include:
- bleeding and infection
- anesthesia risk
- blood clot (DVT/PE)
- progression of arthritis into the other compartments, eventually converting to a total knee
- component loosening or polyethylene wear requiring revision
- persistent pain if patient selection or alignment is off
- periprosthetic fracture (rare)
Revision surgery
OSI also sees patients who need revision of a partial knee replacement — sometimes after an index operation done elsewhere, sometimes after a complication of one of our own. Every surgeon in every practice eventually has a patient with a complication. What matters is how much prevention work goes in on the front end — careful implant sizing, alignment and gap checks, VTE prophylaxis, and infection protocols — and whether the surgeon stands by the patient if a revision is ever needed. Our posture is straightforward: we do everything we can to prevent complications, and we don't walk away when one happens.
The indication to proceed is isolated medial or lateral compartment arthritis with intact ligaments and preserved alignment in a patient who fits the selection criteria. Patients who don't need this operation don't get it.
Further Reading
External patient-education references and related OSI pages for additional background: