Gastrocnemius function – How it assists in knee extension

This attaches above the knee into the femur and into the achilles tendon. It acts in a similar way to soleus, but as it attaches to the femur, its influence on the proximal joints and structures is more significant.

Gastrocnemius decelerates internal rotation of the femur when the foot is on the ground, but it is lengthened at both ends. One end in the frontal plane, the other end in the transverse plane. In the sagittal plane, it controls ankle dorsiflexion.

The knee flexion is transformed into knee extension by a number of muscles along with mass and momentum. As the front leg in gait is moving through towards swing phase, the tibia is slowed down by eccentric lengthening of the gastrocnemius and a number of other calf muscles. This slowing along with the momentum of the body creates knee extension as it pulls back on the distal femur as ankle dorsiflexion is decelerated.

So in function and gait…. the Gastrocnemius are a powerful knee extensor!