The knee is divided into 3 compartments: the lateral, medial, and patellofemoral compartments. In a partial or unicompartmental knee replacement, only 1 compartment of the knee surface is replaced. In total knee arthroplasty, all 3 compartments of the knee are replaced.

Unicompartmental knee replacement is most commonly performed in the medial compartment. Unicompartmental knee replacement is performed infrequently, accounting for 5% of surgeries in which knee arthroplasty is indicated. Unicompartmental knee replacement has advantages over traditional total knee replacement, including faster recovery, less morbidity, and improved preservation of normal knee kinetics.

The 10-year survival rate for unicompartmental knee replacement is 1% to 4%, which compares favorably with reported results for total knee replacement. However, survival of the unicompartmental knee replacement implant diminishes after 10 years, and long-term revision rates are higher than for total knee replacement.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. Hatch D. Unicompartmental Knee Replacement. Orthobullets website. Updated March 12, 2016. Accessed June 27, 2016.
  2. Berger RA, Meneghini M, Jacobs JJ, et al. Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up. J Bone Joint Surg. 2005;87(5):999-1006.
Loading Quiz...