Soleus and gastrocnemius muscle loading decreases anterior tibial translation in anterior cruciate ligament intact and deficient knees.

This study evaluated the effect of the gastrocnemius and soleus muscles on dynamic knee stability by studying the effect of passive calf muscle loading on anterior tibial translation in normal and anterior cruciate ligament (ACL) deficient knees. Anterior tibial translation was measured bilaterally in 12 anesthetized patients with unilateral ACL-deficient knees using a KT-1000 arthrometer. An ankle-foot orthosis was used to passively dorsiflex the ankle and generate tension in the calf muscles. As the ankle flexion angle was progressively changed from 30 degrees plantar flexion to 10 degrees dorsiflexion, anterior tibial translation decreased 43% and 37% with manual maximum force in normal and ACL-deficient knees, respectively (P < .0001). These findings suggest that the calf muscles may function as dynamic knee stabilizers. Anterior tibial translation also was measured in four cadaver knees. Significant decreases were seen in anterior tibial translation with progressive ankle dorsiflexion in ACL-intact specimens and after the ACL had been cut (P < .05). This effect persisted when the gastrocnemius muscle was cut, but was lost when the soleus muscle was released. The data suggest that the soleus muscle may play a role in dynamically stabilizing the knee.