What are the two posterior channel deficits in a double action ankle joint?

The correct choice identifies the deficits associated with a double action ankle joint effectively. In the context of orthotic and prosthetic practice, a double action ankle joint allows for both plantarflexion and dorsiflexion movements.

Foot drop, which refers to the inability to lift the front part of the foot due to weakness or paralysis of the muscles that control dorsiflexion, is a common deficit encountered when there's dysfunction in the posterior channels. This condition can lead to difficulties in walking, as the foot can drag on the ground.

Hyperextension is another critical deficit that can occur when the ankle fails to stabilize correctly during the stance phase of walking. This situation can lead to an increased range of motion at the knee and cause instability, contributing to abnormal gait patterns or even falling if not properly managed with supportive devices or orthotics.

Both of these deficits emphasize the importance of properly functioning posterior channels within the double action ankle joint to maintain proper lower limb mechanics and support stability during ambulation.