Expansion
Dorsiflexion and plantarflexion at the ankle; inversion and eversion at the subtalar joint
Expansion
Ankle (talocrural) joint, a hinge:
- Dorsiflexion (toes up)
- Plantarflexion (toes down)
Subtalar joint:
- Inversion (sole faces inward) - tibialis anterior and posterior
- Eversion (sole faces outward) - fibularis longus and brevis
The ankle is most stable in dorsiflexion, when the wider front of the talus is wedged into the mortise, so sprains usually happen in plantarflexion.