Association between gait mechanics and ultrasonographic measures of femoral cartilage thickness in individuals with ACL reconstruction

Background: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis, which may be in part due to altered gait biomechanics. Articular cartilage thickness is typically imaged using magnetic resonance imaging, which is costly and lacks portability. Ultrasonography may provide an alternative imaging method for articular cartilage. It is unclear if ultrasonographic measurements of cartilage thickness are associated with gait biomechanics in individuals with ACLR. Research Question: To evaluate the association between sagittal and frontal plane knee mechanics during gait and resting femoral cartilage thickness from ultrasonography. Methods: Twenty-five females with ACLR (age = 21.7 +/- 2.6 years, time since ACLR = 60.6 +/- 24.8 months) completed assessments of walking biomechanics and resting femoral cartilage thickness. Linear regression examined the association between gait biomechanics and cartilage thickness at the medial (MC) and lateral (LC) femoral condyles, and intercondylar notch (IC) after accounting for time since ACLR, meniscal injury, and gait speed. Results: In the ACLR limb, larger vertical ground reaction force (Delta R-2 = 0.21, p Delta, = 0.03), knee flexion angle (Delta R-2 = 0.15, p Delta, = 0.05), knee flexion excursion (KFE) (Delta R-2 = 0.16, p Delta, = 0.04), and knee flexion impulse (KFI) (Delta R-2 = 0.23, p Delta, = 0.02) were associated with thicker MC cartilage. A larger knee adduction angle (Delta R-2 = 0.20, p Delta, = 0.03) and knee adduction moment (KAM) (Delta R-2 = 0.20, p Delta, = 0.03) were associated with thinner MC thickness. Larger KFE (Delta R-2 = 0.20, p Delta, = 0.03) was associated with thicker LC cartilage. Gait biomechanics were not associated with IC cartilage thickness. After accounting for co-variates, the combination of KFI and KAM was predictive of MC thickness (Delta R-2 = 0.37, p Delta, = 0.01; Total R-2 = 0.52, p = 0.02). Meniscal injury, KAM, and KFI were significant predictors in the model. In the contralateral limb, KFE was associated with thicker MC cartilage (Delta R-2 = 0.16, p Delta, = 0.05). Significance: Sagittal and frontal plane knee mechanics during gait are uniquely associated with ultrasonographic measurements of femoral cartilage thickness in individuals with ACLR. Furthermore, concomitant medial meniscal injury was associated with thinner MC cartilage.