The medial end of the tibia and the lower fibula project downwards to form a mortise joint, enclosing the trochlear border of the talus. This is a synovial joint that acts as a hinge.
The movements of the foot at the ankle are dorsiflexion (when the toes point up), and plantar flexion (as in ballet, when the toes are pointed down).
The talus articulates with the navicular at the subtalar joint. It is here, and at more distal joints of the foot, that other movements occur.
When trying to point the right big toe to the right, i.e. abduct the right foot, the lateral border of the foot lifts automatically so that the sole slightly faces laterally (eversion). These two movements go together. The opposite (inversion) happens when the foot is adducted.
The medial malleolus of the tibia and the lateral malleolus of the fibula are important landmarks for the anaesthetist.
The long saphenous vein (very useful for intravenous access, particularly in children) passes anterior to the medial malleolus in company with the saphenous nerve.
The posterior tibial artery can be felt behind the medial malleolus and the tibial nerve can be blocked at that point.
The sural nerve is behind the lateral malleolus (midway between the malleolus and the Achilles tendon), and the superficial peroneal nerve is in front. The deep peroneal nerve is midway between the two malleoli anteriorly, deep to the fascial layer, the extensor retinaculum.
Bones of the foot
- Tarsal bones
- Dorsalis pedis artery:The pulse can be felt on the dorsum of the foot between the flexor tendons to the big and second toe at the level of the tarsal bones
- Posterior tibial artery: The pulse can be felt midway between the medial malleolus and the heel
Nerve Supply - sensory and motor
- Medial and lateral plantar nerves (tibial nerve)
- Deep and superficial fibular nerves
- Sural nerve
- Saphenous nerve
The terminal branches of the sensory nerves run between the metatarsals for each toe. They can be blocked at the distal end of the metatarsal space, or at the level of the digits by injection into the web spaces.