BMI Does Not Affect Outcomes in Knee-Replacement Surgery

One of the most pervasive “myths” amongst orthopaedic surgeons is that higher BMI is a contraindication to knee-replacement surgery.

Regular readers, however, will perhaps previous posts on this issue, suggesting that BMI is largely irrelevant in terms of outcomes and benefits for obese patients requiring knee replacements.

This previous finding is further supported by a new paper by David Murray and colleagues from The University of Oxford, UK, published in KNEE.

The researchers prospectively examined the impact of BMI on failure rate and clinical outcomes of 2,438 unicompartmental knee replacements in 378 patients with a BMI less than 25, 856 patients with a BMI 25 to 30, 712 patients with a BMI 30 to 35, 286 patients with a BMI 35 to 40, 126 patients with a BMI 40 to 45 and 80 patients with BMI greater than 45.

At a mean follow-up of 5 years (range 1–12 years) there was no significant difference in the Objective American Knee Society Score between BMI groups.

Although there was a slight trend to decreasing post-operative function scores with increasing BMI, patients with higher BMI had lower scores prior to surgery. Thus, overall higher BMIs were associated with a greater change in functional scores.

Thus, this study, further confirms the notion that obese individual have as much (if not more) to benefit from knee replacement surgery with little evidence that initial BMI adversely affects outcomes.

For clinicians this finding means that there is little evidence to deny knee replacement surgery to individuals with higher BMI levels or require that these patients lose weight prior to surgery.

If you have experience (positive or negative) with knee replacement surgery in overweight and obese patients, I’d like to hear from you.

@DrSharma
Edmonton, AB