The ankle is primarily classified as a hinge joint, rather than a pivot joint. Hinge joints allow for movement in one direction, similar to the way a door opens and closes. In the case of the ankle, it permits the foot to tilt up and down as well as allowing some limited sideways movement.
This means that while the ankle does have some pivot-like movements, especially when considering the subtalar joint underneath it, its main function is that of a hinge. The unique structure of the ankle joint, combined with its surrounding ligaments and muscles, allows for both the stability and mobility necessary for activities such as walking, running, and jumping.