Hi, I am having trouble understanding why weak plantarflexors cause knee hyper extension during mid stance. If the plantar flexors are weak at this phase, wouldent the knee fall into flexion due to poor eccentric control of gastrocs controlling the dorsiflexor moment on the ankle?
Weak plantarflexors could absolutely lead to uncontrolled tibial advancement and, therefore, knee flexion during stance phase.
They could also cause knee hyperextension. Individuals with profound hamstring and/or plantarflexor weakness may have knee hyperextension in mid-stance due to a lack of eccentric control of knee extension (i.e., normally functioning hamstrings or plantarflexors could prevent the knee from snapping into hyperextension).