Asymptomatic and symptomatic individuals with the same radiographic evidence of knee osteoarthritis walk with different knee moments and muscle activity.

There is an established discordance between the structural joint damage and clinical symptoms of knee osteoarthritis; however, there has been little investigation into the differences in joint level biomechanics and muscle activation patterns during gait between symptomatic and asymptomatic individuals with the same radiographic evidence of osteoarthritis. The objective of this study was to examine three-dimensional knee joint biomechanics and muscle activation differences during gait between asymptomatic and symptomatic individuals with radiographic knee osteoarthritis. A total of 54 asymptomatic and 59 symptomatic individuals with a Kellgren-Lawrence osteoarthritis radiographic grade of 2 underwent a comprehensive gait analysis to examine differences in the magnitude and patterns of the knee flexion angle, three-dimensional net resultant moments, and electromyography of the quadriceps, hamstrings, and gastrocnemii during over ground walking between the two groups. The symptomatic group walked with significantly higher overall magnitudes and less mid-stance unloading of the net resultant knee adduction moment, lower peak flexion moments, and higher lateral hamstrings and quadriceps activity during stance than the Asymptomatic group (p < 0.05, sex-adjusted analysis), with a trend (p = 0.07) toward greater transverse plane range of moment over stance. The differences found suggest a "stiffer" frontal and sagittal plane pattern with symptomatic individuals, but with more muscle activity and a trend toward more torsional loading in the transverse plane, which may have implications for shear loading of the joint. This is the first evidence of differences in three-dimensional knee joint biomechanics and muscle activation between asymptomatic and symptomatic individuals with the same radiographic grade.