Article

Knee osteoarthritis patients co-contract in knee-related muscle pairs
during walking. The determinants of this co-contraction remain insufficiently
clear. METHODS: A heterogeneous group of 14 patients was measured before and one
year after knee arthroplasty, and compared to 12 healthy peers and 15 young
subjects, measured once. Participants walked on a treadmill at several imposed
speeds. Bilateral activity of six muscles was registered electromyographically,
and co-contraction time was calculated as percentage of stride cycle time. Local
dynamic stability and variability of sagittal plane knee movements were
determined. The surgeon's assessment of alignment was used. Pre-operatively,
multivariate regressions on co-contraction time were used to identify
determinants of co-contraction. Post-operatively it was assessed if predictor
variables had changed in the same direction as co-contraction time. FINDINGS:
Patients co-contracted longer than controls, but post-operatively, differences
with the healthy peers were no longer significant. Varus alignment predicted
co-contraction time. No patient had post-operative varus alignment. The patients'
unaffected legs were more unstable, and instability predicted co-contraction time
in both legs. Post-operatively, stability normalised. Longer unaffected side
co-contraction time was associated with reduced affected side kinematic
variability. Post-operatively, kinematic variability had further decreased.
INTERPRETATIONS: Varus alignment and instability are determinants of
co-contraction. The benefits of co-contraction in varus alignment require further
study. Co-contraction probably increases local dynamic stability, which does not
necessarily decrease the risk of falling. Unaffected side co-contraction
contributed to decreasing affected side variability, but other mechanisms than
co-contraction may also have played a role in decreasing variability.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS