Passive Muscular Insufficiency: The Etiology of Gastrocnemius Equinus.

The current understanding is that gastrocnemius equinus is caused by a pathologic tightening of the muscle leading to decreased ankle joint dorsiflexion. However, an alternative hypothesis is that it is a normal limitation of available muscle length. Passive muscular insufficiency of the gastrocnemius muscle acts on a pathologic foot, which is poorly prepared to accept the forces from the gastrocnemius-soleus complex. In this manner, a normal gastrocnemius muscle exerts abnormal forces across the foot. This alternative hypothesis leads to a different interpretation of the current research literature and a potential new area of biomechanical research.