The human body

How does the ankle work?

The ankle is the joint that connects the bones in the lower leg to the foot bones. It can be divided into two parts: the upper and lower ankle. 

The upper ankle allows us to move our feet upwards, downwards, and a little to the side. It is made up of three bones:

  • the tibia (shinbone): the main bone in the lower leg,
  • the fibula (calf bone): a second, thinner bone on the outer side of the lower leg, and
  • the talus (anklebone): the foot bone that connects to the shinbone and calf bone. 

The lower ankle connects the anklebone to the bones in the tarsus (the midfoot and hindfoot) and the heel bone. It does not move as much as the upper ankle. The lower ankle allows the foot to tilt to the side a bit and also turn inwards and outwards. Turning your foot outwards is known as pronation, and turning it inwards is called supination.   

Illustration: Healthy ankle, seen from above and from the side - as described in the articleHealthy ankle, seen from above and from the side

Cartilage, tendons and ligaments  

In healthy joints, the ends of bones are covered with a layer of cartilage. If this cartilage is healthy, it is very smooth and hard, but also elastic. It acts as a shock absorber and reduces friction. Tendons, ligaments and the joint capsules hold the joint together and help it to move. Tendons connect muscles to bones. Ligaments connect bones to bones and help keep the joint stable.  

Ankle ligaments are tough, elastic bands of connective tissue that connect bones in the joint, keeping them tightly together. Because the ankle joint is made up of many bones, there are also a lot of ligaments to stabilize and strengthen it. Three ligaments run along the outside of the ankle, and one ligament (consisting of four bands of tissue) runs along the inside of the ankle.  

Stability and vulnerability  

The ankle joint has to withstand a lot of weight and force. When you run and jump, for instance, your ankles have to carry forces equivalent to several times your body weight. If the strain is too big, the ligaments might overstretch or tear (rupture).  

One common injury happens when a foot lands in an awkward position and bends outwards. This can injure the outer ankle ligaments. Injuries to the ligament on the inner side of the ankle are less common.  

Stretched and torn ankle ligaments are among the most common injuries. Because the lower ankle is more stable than the upper ankle, ankle injuries such as strains, sprains and fractures nearly always only affect the upper ankle.

Illustration: Ankle injuries: Grade I, II and III sprains - as described in articleAnkle injuries: Grade I, II and III sprains

Illustration: Ankle injuries: Fracture of inner and outer ankle - as described in the articleAnkle injuries: Fracture of inner and outer ankle