Co-activation
differences in lower limb muscles between asymptomatic controls and those with
varying degrees of knee osteoarthritis during walking.
Hubley-Kozey, C., Hill, N., Rutherford, D.,
Dunbar M., Stanish, W. Clinical Biomechanics, 2009; 24, 407 – 414.
63 asymptomatic, 59 moderate and 48 severe
OA subjects were recruited for the study purposes. All subjects completed standardized
protocols for motion capture and electromyographical analysis of six lower
extremity muscles (vastus lateralis, vastus medialis, the lateral and medial
hamstrings, and the lateral and medial gastrocnemius).
Severe OA had higher amplitudes for the two vasti muscles and the two
hamstrings for most of stance phase compared to both the moderate OA and the asymptomatic groups. The
moderate OA group had elevated activity for the vastus lateralis and lateral
hamstring only compared to the asymptomatic group. While walking velocity has
been shown to affect EMG amplitude the expected finding would be a decrease in
activation with a decrease in walking velocity based
on previous studies. This was not the case since the severe OA group walked slower than the
other two groups and had higher EMG amplitudes for quadriceps and hamstrings
muscles. Authors stated that these results have important clinical
implications. According to them, valgus unloader braces and lateral heel wedges
aimed at the medial–lateral joint loading imbalance may be more effective in
the moderate OA that display high lateral co-activation and normal medial
co-activation. In contrast bracing aimed to improve overall joint stability may
be more effective for those with more severe knee OA who have a general
increase in co-activity.
This study seems to confirm generally
accepted notion among clinicians, that increased muscle activation is aimed at
reducing load and excessive motion within joints affected by OA, and therefore preventing
those patients from pain symptoms.
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