Does body mass index affect the outcome of unicompartmental knee replacement?

Knee. 2013 Dec;20(6):461-5. doi: 10.1016/j.knee.2012.09.017. Epub 2012 Oct 27.


Background: Obesity is considered to be a contraindication for unicompartmental knee replacement (UKR). The aim was to study the impact of BMI on failure rate and clinical outcome of the Oxford mobile bearing UKR.

Method: Two thousand four hundred and thirty-eight medial Oxford UKRs were studied prospectively and divided into groups: BMI<25 (n=378), BMI 25 to <30 (n=856), BMI 30 to <35 (n=712), BMI 35 to <40 (n=286), and BMI 40 to <45 (n=126) and BMI≥45 (n=80).

Results: There was no significant difference in survival rate between groups. At a mean follow-up of 5years (range 1-12years) there was no significant difference in the Objective American Knee Society Score between groups. There was a significant (p<0.01) trend with the Oxford Knee Score (OKS) and Functional American Knee Society Scores decreasing with increasing BMI. As there was an opposite trend (p<0.01) in pre-operative OKS, the change in OKS increased with increasing BMI (p=0.048). The mean age at surgery was significantly (p<0.01) lower in patients with higher BMI.

Conclusions: Increasing BMI was not associated with an increasing failure rate. It was also not associated with a decreasing benefit from the operation. Therefore, a high BMI should not be considered a contra-indication to mobile bearing UKR.

Level of evidence: IV.

Keywords: Obesity; Outcomes; Unicompartmental knee replacement.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Arthroplasty, Replacement, Knee / adverse effects
  • Arthroplasty, Replacement, Knee / methods*
  • Body Mass Index*
  • Cohort Studies
  • Databases, Factual
  • Female
  • Follow-Up Studies
  • Humans
  • Knee Prosthesis
  • Male
  • Middle Aged
  • Minimally Invasive Surgical Procedures / adverse effects
  • Minimally Invasive Surgical Procedures / methods
  • Obesity / diagnosis*
  • Obesity / epidemiology
  • Prosthesis Design
  • Prosthesis Failure / trends*
  • Recovery of Function
  • Retrospective Studies
  • Risk Assessment
  • Treatment Outcome