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Q&A Topic: Partial Knee Replacement With a Mobile Bearing Prosthesis

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David J. Yasgur, MD, FAAOS

Q. How does a normal knee work versus a knee that needs to be replaced? 

A. A normal knee is not painful and does not limit your mobility. In an arthritic knee, especially one with advanced osteoarthritis, the protective cartilage surface has worn away causing bone to rub against bone.

Q. How do I know if I qualify for a partial or total knee replacement?

A. Your doctor will determine which type of replacement you need based on a physical exam and x-rays. Knee replacements are done only for people whose osteoarthritis is severe. Historically, physicians have favored total knee replacements over partial for almost all patients with severe osteoarthritis because they last longer than “fixed-bearing” partial knees. But a technologically-advanced prosthesis known as the “mobile-bearing” knee is challenging that thinking. Unlike traditional fixed-bearing partial knees, the mobile-bearing knee lasts nearly as long as a total knee replacement.S tudies have shown that twenty years post-implant, the mobile-bearing knee is still viable in 91 percent of patients. The comparable figure for total knee replacements is 93 percent.

Q. What advantages does a partial knee replacement with a mobile- bearing device have over a total knee replacement?

A. The mobile-bearing knee is now considered to be the gold-standard of partial knee replacement. The main advantages are faster recovery time, less pain and a more flexible knee.  Total knee replacement is major surgery involving the removal of a substantial portion of bone in the knee and half the supporting ligaments. The less invasive partial knee replacement preserves all the ligaments and two-thirds of the healthy knee. Patients can often go home the same day and recovery time is cut in half.

Q. How does the “mobile-bearing knee” differ from a “fixed-bearing knee?”

A. Key to the durable nature and natural feel of the mobile-bearing knee is a plastic bearing that glides freely throughout the knee’s range of motion, hence the name “mobile-bearing.” Similar to the ball bearings that “bear the weight” and allow a wheel to turn freely, a mobile bearing allows your knee to move more naturally. In other partial knees, known as “fixed-bearing,” the bearing does not move.

Q. Is the mobile-bearing partial knee right for everyone?

A. The device can be used in patients with severe osteoarthritis regardless of age, weight or activity level if the arthritis is limited to the inner or medial compartment of the knee and the ligaments are intact. About 30 to 40 percent of patients meet these criteria.

Q.  What risks are associated with the mobile-bearing knee? A. Even though a partial knee replacement is typically a 70-minute surgical procedure, it still comes with the same risks associated with major surgery, such as infection, blood clots and reaction to anesthesia. Complications associated with the mobile-bearing knee include “spin-out,” when the bearing dislocates as a result of a sprain or over-extended ligaments. The complication is rare, occurring in one out of every 200 patients.

Learn More About Dr. Yasgur
Director of Quality and Outcomes
Orthopedic and Spine Institute
Northern Westchester Hospital

Northern Westchester Hospital is a proud member of Northwell Health.

Read Past Topics from Dr. Yasgur: 
Chronic Knee Pain and Knee Replacement
Hip Replacement Surgeries
Patient-Specific Instruments for Total Knee Replacement
Management of ACL Tears


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