What is the primary dorsiflexor of the ankle?

The primary dorsiflexor of the ankle is the tibialis anterior. This muscle originates at the lateral condyle and upper two-thirds of the tibia and inserts into the medial cuneiform and first metatarsal bones of the foot. Its main function is to bring the foot upward toward the shin, which is the action known as dorsiflexion. Dorsiflexion is crucial for various movements, such as walking and running, as it allows the heel to strike the ground while the toes are lifted.

The other muscles listed serve different functions that do not primarily involve dorsiflexion. The soleus and gastrocnemius, for instance, are primarily responsible for plantarflexion, the action of pointing the toes downward, particularly important in pushing off during walking. The peroneus longus assists in eversion of the foot and can help in plantarflexion but does not serve as the main muscle for dorsiflexion. Therefore, the role of the tibialis anterior as the primary dorsiflexor makes it the correct answer in this context.