Altered gait mechanics and elevated serum pro-inflammatory cytokines in asymptomatic patients with MRI evidence of knee cartilage loss.

Abstract

To test if sagittal plane gait mechanics parameters and serum inflammation levels differ between healthy asymptomatic subjects and asymptomatic subjects with magnetic resonance imaging (MRI) evidence of cartilage loss. Gait mechanics and resting serum tumor necrosis factor-α (TNFα) concentrations were measured for two groups of asymptomatic subjects recruited for a previous study: Pre-Osteoarthritis (OA) subjects had MRI evidence of partial- or full-thickness knee cartilage loss in at least one compartment (n=52 (30 female), 1.7±0.1m, 85.3±18.9kg, 44±11 years); Control subjects had no MRI features of cartilage loss, osteophytes, bone marrow lesions, nor meniscal pathology in either knee (n=26 (13 female), 1.7±0.1m, 74.6±14.9kg, 34±10 years). Discrete measures of sagittal plane gait kinematics and kinetics were compared between subject groups and adjusted for age and body mass index (BMI) using analysis of covariance (ANCOVA). Serum TNFα concentrations were compared between groups using bootstrap t-test. The Pre-OA group had less extended knees (P=0.021) and decreased maximum external knee extension moment (P=0.0062) in terminal stance during gait, as well as increased resting serum TNFα concentration (P=0.040) as compared to Control subjects. There were no group differences in heel strike flexion angle (P=0.14), in maximum knee flexion moment (P=0.91), nor in first peak knee adduction moment (KAM) (post-hoc analysis, P=0.39). The finding that asymptomatic subjects with cartilage loss had gait and inflammatory characteristics similar to those previously reported in symptomatic OA patients supports the idea that there are specific mechanical and biological factors that precede the onset of knee pain in the pathogenesis of OA.