Effects of BMI on Walking Speed and Gait Biomechanics after Anterior Cruciate Ligament Reconstruction

Abstract

Purpose History of an anterior cruciate ligament reconstruction (ACLR) and high body mass index (BMI) are strong independent risk factors for knee osteoarthritis (KOA) onset. The combination of these risk factors may further negatively affect joint loading and KOA risk. We sought to determine the combined influence of BMI and ACLR on walking speed and gait biomechanics that are hypothesized to influence KOA onset. Methods Walking speed and gait biomechanics (peak vertical ground reaction force [vGRF], peak vGRF instantaneous loading rate [vGRF-LR], peak knee flexion angle, knee flexion excursion [KFE], peak internal knee extension moment [KEM], and peak internal knee abduction moment [KAM]) were collected in 196 individuals with unilateral ACLR and 106 uninjured controls. KFE was measured throughout stance phase, whereas all other gait biomechanics were analyzed during the first 50% of stance phase. A 2 × 2 ANOVA was performed to evaluate the interaction between BMI and ACLR and main effects for both BMI and ACLR on walking speed and gait biomechanics between four cohorts (high BMI ACLR, normal BMI ACLR, high BMI controls, and normal BMI controls). Results History of an ACLR and high BMI influenced slower walking speed (F 1,298 = 7.34, P = 0.007), and history of an ACLR and normal BMI influenced greater peak vGRF-LR (F 1,298 = 6.56, P = 0.011). When evaluating main effects, individuals with an ACLR demonstrated lesser KFE (F 1,298 = 7.85, P = 0.005) and lesser peak KEM (F 1,298 = 6.31, P = 0.013), and individuals with high BMI demonstrated lesser peak KAM (F 1,297 = 5.83, P = 0.016). Conclusion BMI and history of ACLR together influence walking speed and peak vGRF-LR. History of an ACLR influences KFE and peak KEM, whereas BMI influences peak KAM. BMI may need to be considered when designing interventions aimed at restoring gait biomechanics post-ACLR.

Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics

“…We chose to simultaneously compare absolute kinetics between our groups to further understand how overweight/obesity may uniquely contribute to gait biomechanics in those with ACLR, where previous research has only compared normalized kinetics 20 . A variety of features such as kinematic patterns and gait speed may influence the magnitude of joint moments independently of obesity, and evaluation of absolute and normalized values allows for a more robust group comparison where body size is a factor of interest.…”

“…Cohen's d effect sizes and 95% confidence intervals were calculated to further interpret the magnitude of differences in comparisons made between absolute versus normalized kinetic outcomes by BMI group. We did not adjust for gait speed as it violates the independence assumption of analysis of covariance (ANCOVA) since it is associated with the main effects of both high BMI and ACLR status, 9,10,20 and thus, differences between groups in gait speed should be expected. We also explored for associations between time since ACLR and gait outcomes using the Pearson correlation as a potential confounder in analyses.…”

“…Individuals with ACLR and overweight/obese BMI had slower gait speed, and individuals with overweight/obese BMI (with or without ACLR) had a lower external knee adduction moment compared with those with normal BMI 20 . Moreover, individuals with ACLR had lower internal knee extensor moments than those without ACLR 20 . However, this study included groups that were substantially uneven in sex distribution 20 .…”

“…To our knowledge, only a single study has evaluated the interaction between a history of ACLR and high BMI on gait biomechanics 20 . Individuals with ACLR and overweight/obese BMI had slower gait speed, and individuals with overweight/obese BMI (with or without ACLR) had a lower external knee adduction moment compared with those with normal BMI 20 . Moreover, individuals with ACLR had lower internal knee extensor moments than those without ACLR 20 .…”

A Review of the Relationships Between Knee Pain and Movement Neuromechanics

“…60 The ACLR patients exhibit similar biomechanical alterations, including decreased vertical GRF, knee-flexion angle, and internal kneeextension moment, 61,62 even after pain resolution. 63 The ACLR researchers have hypothesized that abnormally decreased or increased loads associated with knee pain are detrimental to long-term joint health. 64 Although altered biomechanics and AMI are known to persist for ACLR patients, often years after pain resolution, neuromechanical changes may still be initially caused, at least partly, by pain associated with the ACL injury or ACLR.…”