Weak associations between body mass index and self-reported disability in people with unilateral anterior cruciate ligament reconstruction

Purpose and hypothesis

Individuals with an anterior cruciate ligament reconstruction (ACLR) are susceptible to persistent disability, weight gain and the development of knee osteoarthritis. It remains unclear whether body mass index (BMI) is a factor that influences disability following ACLR. The purpose of this study was to determine the association between BMI and self-reported disability [International Knee Documentation Committee (IKDC) Index] in individuals with a unilateral ACLR. We hypothesized that lower BMI would associate with higher IKDC.

Methods

BMI and IKDC were measured in 668 individuals with a unilateral ACLR (60.9% female, BMI 24.4 ± 3.7 kg/m², IKDC 84.7 ± 11.9%). Bivariate associations were conducted between BMI and IKDC for the entire sample and selected subsets (gender, ACLR graft type and history of meniscal injury). Multiple regression analyses were used to determine the impact of potential covariates (Tegner score, age and months since ACLR) for significant bivariate associations. After accounting for covariates, there were no significant associations between BMI and IKDC when separately evaluating the cohort based on either gender or history of a concomitant meniscal injury. The odds of achieving age- and gender-matched healthy population average IKDC scores for those with low (<25) and high (≥25) BMI were determined.

Results

Lower BMI associated with higher IKDC (r = ?0.08, P = 0.04). For the entire sample, BMI did not uniquely predict variance in IKDC (ΔR ² > 0.001, n.s.) after accounting for covariates. BMI uniquely predicted a significant but negligible amount of variance in IKDC in individuals with a patellar tendon autograft (ΔR ² = 0.015, n.s.). Individuals with low BMI demonstrated higher odds (odds ratio = 1.45; 1.05–1.99) of achieving population average IKDC scores compared to participants with high BMI.

Conclusions

There was a significant but negligible correlation between lower BMI and lesser disability in individuals with unilateral ACLR and individuals who are underweight or of normal BMI demonstrated higher odds of achieving population average IKDC scores compared to overweight or obese individuals. While an overall association was found between lower BMI and lesser disability, the magnitude of the association remains negligible; therefore, BMI was not a strong clinical predictor of successful ACLR outcomes in this cohort of patients with unilateral ACLR.

Level of evidence

Cross-sectional prognostic study, Level II.