Article

Increased muscle co-contraction during gait is common in individuals with knee
pathology, and worrisome as it is known to amplify tibiofemoral compressive
forces. While knees with articular cartilage defects (ACD) are more vulnerable to
compressive forces, muscle co-contraction has never been reported in this
population. The purpose of this study was to evaluate the extent to which
individuals with ACDs in the knee demonstrate elevated quadriceps to hamstrings
muscle co-contraction on the involved limb during gait compared to the uninvolved
limb and to healthy controls. We also explored the impact of participant
characteristics and knee impairments on co-contraction. Twenty-nine individuals
with full-thickness knee ACDs (ACD group) and 19 healthy adults (control group)
participated in this study. Participants performed five gait trials at
self-selected speed, during which activity of the quadriceps and hamstrings
muscles were collected with surface electromyography. Three-dimensional motion
capture was used to define phases of gait. Quadriceps strength and self-reported
outcomes were also assessed in the same session. There were no differences in
quadriceps: hamstrings co-contraction between the ACD and control groups, or
between the involved and uninvolved limb for the ACD group. For both ACD and
control groups, co-contraction was highest in early stance and lowest in late
stance. Quadriceps strength was consistently the strongest predictor of muscle
co-contraction in both the ACD and the control groups, with individuals with
lower strength demonstrating greater co-contraction. Further study is needed to
understand the effect of increased muscle co-contraction on joint compressive
forces in the presence of varied quadriceps strength.
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