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Unicompartmental Knee Replacement


The most common cause of chronic knee pain is arthritis. A unicompartmental knee replacement, or partial knee replacement, is a surgery performed when one part of a patient’s knee is severely damaged by arthritis causing daily activities to become hard to perform. A patient’s arthritis can often progress to a point where there is pain with walking, climbing stairs, and even resting. Partial knee replacement surgery offers a less painful and invasive alternative to a total knee replacement when only one compartment of the joint is affected. It can help to relieve pain and restore function to a damaged portion of the knee making an impact in a patient’s life. With new innovations and advancements, total knee replacements have continued to improve over the past decade with more capabilities, improved results, and longevity than ever before.



The knee joint is formed by the junction of the femur (thighbone), tibia (shinbone), and patella (kneecap), which are all lined with articular cartilage. This cartilage along with the menisci protects and cushions the knee joint. However, overtime knee arthritis or the painful inflammation and stiffness of the knee joint can develop and cause degeneration of the cartilage. One specific type of arthritis is osteoarthritis, which is the wear and tear of the cushioning surfaces of the knee overtime. Osteoarthritis can affect one of the three compartments of the knee: medial (inside), lateral (outside), or patellofemoral (kneecap) without affecting the entire knee. The most commonly affected compartment is the medial side of the knee.

Clinical Evaluation

At the time of your appointment, the surgeon will take a detailed history, perform a physical exam, and take x-rays of your knees. From these x-rays, the severity and location of degeneration can be assessed. Treatment and outcomes will be discussed at this time and a plan will be put into place. Your candidacy for this procedure will be discussed with the surgeon prior to surgery.

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Non-Operative Treatment

Conservative treatment of arthritis related knee pain is almost always exhausted before a knee replacement is considered. Treatment plans include injections, medication, weight loss, physical therapy, strengthening, or bracing. Partial knee replacement surgery is not a decision to be taken lightly and needs significant planning, commitment, and rehabilitation to have a successful and positive outcome.

Operative Treatment

Surgical management of severe unicompartmental osteoarthritis involves a partial knee replacement. Surgical indications for successful unicompartmental replacement require that a patient’ symptoms be related to degenerative arthritis within a single compartment of the knee. During surgery, the damaged bone and cartilage of the knee is removed, resurfaced, and replaced with part of an artificial knee joint. A partial knee replacement consists of two metal implants with a plastic spacer between them. The ligaments and unaffected cartilage of the knee are left in place providing a less invasive and more biologic solution. A partial knee replacement as opposed to a total knee replacement offers a quicker recovery time, less pain after surgery, and can be accomplished in an outpatient setting. The goal of this procedure is for the patient to successfully return to daily activity with improvement in symptoms and a better quality of life in 3-6 months. A general guideline of Partial Knee Replacement rehabilitation can be found within the Rehabilitation Protocols.

Download a PDF of this information.

Download the physical therapy protocol for this condition.

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