Anatomy of the Ankle & Foot

The ankle is a small and flexible joint that also has to be strong and stable enough to support the entire weight of the body when we stand on one leg. The foot is nearly always our only connection to the ground and needs to be able to absorb the shock and pressure caused by the movements of standing, walking, running and jumping.

The two lower leg bones, the tibia and fibula, and the bone that sits above the heel of the foot, the talus, all meet at the ankle. 70% percent of the talus is covered with cartilage - the meeting point for so many bones it requires lots of protection and shock absorption.

The end of the tibia forms the medial malleolus, which you can see protruding from the inside of the ankle, and the posterior malleolus at the back of the ankle. The lower end of the fibular can be felt on the outside of the ankle and is referred to as the lateral malleolus. All of these together are called the malleoli.

Talocrural joint

The joint that connects the lower ends of the fibula and tibia with the talus is a synovial hinge joint, which is the same type of joint as the knee. This particular joint of the ankle has several names including the talocrural joint, ankle joint, tibiotalar joint, talar mortise or talar joint.

The aforementioned malleoli help to stabilise the talus, by forming a ‘dish’ shaped, rectangular socket (mortise) that a groove in the talus (trochlea) fits into. This helps to prevent extreme movement of any of the bones which could cause damage to the ankle joint. This joint is responsible for the up and down movement of the foot.

The majority of the weight that the joint has to bear is held at the tibia and talus rather than at the joint between the fibula and talus.

Subtalar joint

The subtalar joint sits below the talocrural joint, and connects the talus to the calcaneous (the bone that makes the hard ball of the foot). This joint is important for the foot to absorb and disperse shock effectively and to keep the ankles and legs aligned properly. This is achieved by the joint allowing the foot to roll slightly inwards (pronation) and outwards (supination). Too much movement in either direction of roll can cause injuries such as sprains, shin splints or knee problems. This joint is responsible for the side-to-side movement of the foot.

Talonavicular joint

This joint is formed by the talus and the navicular, the foot bone that lies immediately in front of the talus. This joint connects the back and middle of the foot together, and is responsible for the circular rolling movement of the foot.

Ankle & foot related AnatomyStuff resources:

Flexible Foot and Ankle Model
Foot and Ankle Anatomy Chart
Injuries of the Foot and Ankle Anatomy Chart
Budget Foot and Ankle Model with Ligaments
Strengthening the Foot and Ankle Chart / Poster - Laminated

Further reading / sources 
 
The ankle joint:
https://www.kenhub.com/en/library/anatomy/the-ankle-joint 
The structure of the ankle joint:
https://www.physio-pedia.com/Foot_and_Ankle_Structure_and_Function 
Subtalar joint:
https://www.verywellhealth.com/what-is-the-subtalar-joint-1337686  
Subtalar joint motion:
https://ouhsc.edu/bserdac/dthompso/web/gait/KNMATICS/STJOPEN.HTM  
Talonavicular joint:
https://footeducation.com/rheumatoid-arthritis-talonavicular-joint/  
Pronation:
https://www.healthline.com/health/beginners-guide-to-pronation#2 

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