What is the primary action of the gastrocnemius muscle at the ankle joint?

• A. Inversion of the foot
• B. Dorsiflexion of the foot
• C. Eversion of the foot
• D. Plantar flexion of the foot

Answer: (D)

Verified step by step guidance

1. Identify the anatomical location and function of the gastrocnemius muscle. It is a major muscle located in the posterior compartment of the lower leg, forming part of the calf.
2. Understand the movements at the ankle joint. The primary movements include dorsiflexion (lifting the foot upwards), plantar flexion (pointing the foot downwards), inversion (turning the sole inward), and eversion (turning the sole outward).
3. Recall that the gastrocnemius crosses the posterior aspect of the ankle joint and attaches to the calcaneus via the Achilles tendon, which allows it to exert force that points the foot downward.
4. Recognize that because of its position and attachment, the gastrocnemius muscle's primary action at the ankle joint is to produce plantar flexion of the foot.
5. Confirm that the other options (inversion, dorsiflexion, eversion) are actions performed by different muscles, not the gastrocnemius.