The knee is divided into 3 compartments: medial, lateral, and patellofemoral. Unicompartmental knee arthroplasty may be performed in all 3 compartments, with the medial compartment being the most commonly replaced. The decision to undergo TKA vs UKA is controversial and is up to the discretion of the surgeon. The indication for UKA includes arthritis isolated to 1 compartment of the knee. Radiographs, magnetic resonance imaging, and/or diagnostic arthroscopy are often used to confirm that no arthritis exists in the remaining 2 compartments before a UKA is performed.

A downfall of UKA is a higher revision rate compared with TKA. Much like TKA, revision surgery after UKA may be due to implant loosening or infection. Revision surgery after UKA may also result from progressive lateral or medial compartment arthritis. Benefits of UKA include improved physiologic function, a shorter hospital stay, and a shorter rehabilitation period. UKA is more cost-effective than TKA in patients older than 65 years of age due in large part to lower rehabilitation costs. Improved physiologic function after UKA results from preserving both cruciate ligaments, which often feels more like a “normal” knee compared with TKA. TKA is associated with a higher risk of postoperative complications such as arthrofibrosis, postoperative anemia requiring transfusion, infection, and thromboembolic events.1,2

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).


  1. Brown NM, Sheth N, Davis K, et al.  Total knee arthroplasty has higher postoperative morbidity than unicompartmental knee arthroplasty: a multicenter analysis. J Arthroplasty. 2012;27(8):86-90.
  2. Argenson J, Blanc G, Aubaniac J, Parratte S. Modern unicompartmental knee arthroplasty with cement: a concise follow-up, at a mean of twenty years, of a previous report. J Bone Joint Surg Am. 2013;95(10):905-909.
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