The Effect of Body Mass Index on Functional Outcome of Patients With Knee Replacement

Objective: To investigate the effects of body mass index (BMI) on the rehabilitation process in patients with a recent knee replacement.

Design: This retrospective cohort study included all patients admitted to a rehabilitation hospital, with a recent diagnosis of knee replacement and available hospital admission data including height and weight, between 2014 and 2017.

Setting: Rehabilitation hospital.

Participants: Study participants included patients who had undergone knee replacement surgery (N=742), with available BMI data.

Interventions: None.

Main Outcome Measures: FIM scores, including FIM change per day (FIM efficiency) by BMI category.

Results: The chart review identified 742 patients who had undergone knee replacement surgery, with available BMI data. The identified patients ranged in age from 58 to 85 years, with a mean age of 70 years. Of the patients included in the study, 24 were male, 49 were female, 73 were within the normal weight class, 180 in the overweight class, 189 in the obese class I, 143 in the obese class II, and 157 patients were classified as obese class III. The mean FIM efficiency was highest in the obese class II category (3.96). In a multivariate analysis after controlling for age, obese classes II and III had significantly better FIM efficiency.

Conclusion: This study did not demonstrate that obesity adversely affects the rate of recovery during hospitalization after knee replacement surgery.