A unicompartmental arthroplasty is the replacement with a prosthetic of just one of the three compartments of the knee when it is affected by the condition of severe osteoarthritis (OA). Musculoskeletal providers divide the knee into three compartments: medial (inside) compartment, lateral (outside) compartment, and the kneecap on the femur (patellofemoral joint). Osteoarthritis is a systemic inflammatory condition that affects the entire joint, causing aching, swelling, stiffness, and deformities. One of its physiological signs is to degrade the cartilage lining of the bones. Usually, it affects the cartilage in more than one compartment, but occasionally, a patient only has one compartment affected.

Patients who have one compartment of their knee affected by OA tend to be younger, history of previous trauma or injury, and well-controlled weight (Body Mass Index less than 30-35). As the disease progresses, the signs and symptoms worsen in severity and their effect on daily living. There are non-surgical treatment options such as oral medications, topical creams, bracing, home exercise program, and injection therapy. However, when a healthy patient has tried the conservative treatment, and it is no longer working, they are unable to participate in their own care/lifestyle/work effectively, and sleep is affected, surgical intervention is considered. The definitive surgical treatment for only one compartment affected by osteoarthritis is a unicompartmental arthroplasty. For the purposes of this article, we are going to focus on the patellofemoral unicompartmental arthroplasty.

Patients whose patellofemoral compartment (kneecap with femur bone) is severely affected by their osteoarthritis have difficulty with kneeling, squatting, sit to stand/stand to sit, stairs, and incline/decline (ladders, hills). The arthroplasty implant replaces the undersurface of the patella with a polyethylene surface (plastic) and the femoral surface (aka. trochlear groove) with a metal surface. It is cemented in place like the total knee arthroplasty. The surgical incision for this implant is similar to a total knee arthroplasty, but there is less procedure involved. A less invasive procedure leads to less pain and a faster recovery for patients. Patients are weight-bearing as tolerated with a walker after the procedure, and physical therapy is required. However, these patients tend to take less time to recover compared to patients who have had a total knee arthroplasty. There are risks to consider with any surgical procedure. Any patient with unicompartmental osteoarthritis can develop OA in other compartments in the future and require revision surgery to switch them from a unicompartmental arthroplasty to a total knee arthroplasty.

The diagnosis of osteoarthritis is made with X-rays and an evaluation by a musculoskeletal provider. They will be able to evaluate the severity of the disease and where the patient is in the treatment process. If you are having knee pain, please don’t hesitate to make an appointment.

James Davidson, MD and Katie Fultz, PA-C

Blanchard Valley Orthopedics and Sports Medicine