Walking Speed As a Potential Indicator of Cartilage Breakdown Following Anterior Cruciate Ligament Reconstruction

Objective. To determine whether or not self-selected walking speed associates with serum biomarkers of cartilage (collagen and proteoglycan) breakdown in anterior cruciate ligament reconstructed (ACLR) individuals. Methods. Twenty individuals with a history of a primary unilateral ACLR participated in this cross-sectional study. Resting blood was collected from each participant prior to completing 5 walking gait trials at a self-selected comfortable speed. Walking speed was evaluated in a 3-dimensional motion capture laboratory and determined from the velocity of the pelvic center of mass. Sera were assessed for collagen type II cleavage product (C2C) and proteoglycan (aggrecan) concentrations using commercially available specific enzyme-linked immunosorbent assays. Pearson's product-moment (r) and Spearman's (p) correlations were used to evaluate associations between walking speed and biomarkers of cartilage breakdown metabolism. Partial correlations were used to determine whether covariates influenced associations between walking speed and biomarkers of cartilage breakdown. Results. ACLR individuals with a slower walking speed demonstrated higher concentrations of serum C2C (r = -0.52, P = 0.02), while there was no significant association between walking speed and aggrecan concentrations (p = -0.29, P = 0.31). After accounting for the variance associated with stance phase duration, ACLR individuals with a slower walking speed still demonstrated greater serum C2C concentrations (partial r = -0.53, P = 0.02). Conclusion. ACLR individuals who habitually walk slower may experience a greater degree of collagen breakdown, suggesting that walking speed may be a future useful clinical indicator for identifying individuals with higher levels of cartilage breakdown and preradiographic osteoarthritic joint changes.