Ankle 足踝

Ankle is a joint made of 4 bones, Tibia and fibula (the shin bone), talus (the ankle bone) and calcaneum (the heel bone). This ankle joint proper allow good planar motion of ankle up and down (called ankle dorsiflexion when up and plantarflexion when down). It also allows some rotation of the heel to accomodate slanting ground. Therefore, in theory, the ankle should involve the midfoot, which has 5 more bones, cuboid, navicula and 3 cuneiforms.

The talus is sitting in a mortise like structure formed by the two shin bones. Apart from the bony contour which offers good stability, it has strong ligaments on either side. The outer ligaments are frequently involved in sprain injury. When these ligament is torn, there will be abnormal translation and rotation. This sense of instability is particularly obvious when one descending on stairs especially with pivoting, i.e. on platform between two flights of stairs.