- The ankle joint, also known as the talocrural joint, is a synovial joint.
- More specifically, it is a uniaxial hinge joint.
- It is formed by the distal ends of the tibia and fibula meeting the talus.
- It allows motion in all one cardinal plane:
- dorsiflexion/plantarflexion of the foot in the sagittal plane.
NOTES:
- The ankle/talocrural joint should not be confused with the subtalar joint. Pronation and supination of the foot occur primarily at the subtalar joint, NOT at the talocrural joint.
- Sometimes the subtalar joint is described as the lower ankle joint.
- The talocrural joint is often described as being like a mortise (carpentry) joint; however, many people are not familiar with the carpentry term mortise joint. Perhaps a better analogy would be to describe the talus like a nut held in a wrench (the wrench being the tibia and fibula).
- There is a lot of confusion with naming joint actions of the foot at the ankle/talocrural joint. Technically, flexion is “pointing the toes,” in other words, straightening out the ankle joint; and extension is bending the ankle joint (bringing the foot back toward you). For this reason, the terms dorsiflexion and plantarflexion are generally used instead.
- Dorsiflexion and plantar flexion are not perfectly in the sagittal plane. They are oriented outward from the sagittal plane a bit.
- The reverse closed-chain joint actions of movements of the leg (tibia/fibula) relative to the foot (talus) can also occur at the ankle joint. These movements would be described as extension (dorsiflexion) and flexion (plantarflexion) of the leg at the ankle joint. They occur during the gait cycle when we walk.