How your ankle works – a quick anatomy lesson on a very complex joint

29 Nov

ankle anatomy Running, jumping, walking, weight bearing – your ankle does it all. This remarkable joint is comprised of a series of structures that create a hinge – a very complex hinge with many moving parts, which can withstand 1.5 times your body weight when you walk and up to eight times your body weight when you run.

The major components of your ankle

The ankle is actually two joints: the subtalar joint, and the true ankle joint. Holding it all together are blood vessels, muscles, nerves, ligaments, tendons, bones and joints.

Bones & Joints

The ankle joint is formed by three bones:

  • the ankle bone, or talus
  • the lower end of the shinbone, or tibia
  • the small bone of your lower leg, or fibula

The bones fit together as shown below: the top of the talus fits inside a socket created by the lower end of the tibia and the fibula. The bottom of the talus sits on the heelbone, called the calcaneus. The talus works like a joint inside this socket to allow your foot to move up in direction, called dorsiflexion, or down, called plantarflexion.

ankle anatomy

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To keep the joint moving smoothly, the bones inside it are covered with articular cartilage, a lining  1/4 inch thick which also serves as a shock absorber.

Ligaments

Ligaments are soft tissues which connect bones with bones, and are similar to tendons, which attach muscle to bone. Ligaments and tendons are composed of small fibers of collagen, which bundle together into structures which look much like rope. The strength of tendons and ligaments is determined by how thick they are.

Ligaments appear on both sides of the ankle joint. On the outside of your ankles, three ligaments comprise the lateral ligament complex: the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The inside of each ankle, referred to as the medial ankle, is supported by the deltoid ligament.

anatomy ankle ligaments

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Three ligaments also support the “hinge” where the bottom end of the fibula meets the tibia: the anterior inferior tibiofibular ligament (AITFL) crosses just above the front of the ankle, connecting the tibia to the fibula; the posterior fibular ligaments attach across the back of the tibia and fibula, called the posterior inferior tibiofibular ligament (PITFL), and the transverse ligament. Additionally, a long sheet of connective tissue running between the tibia and fibula, from knee to ankle, is called the interosseous ligament.

ankle ligaments

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All of the ligaments surrounding the ankle joint are part of the joint capsule, a watertight sac that forms around all of the joints in your body.

Tendons

The most well known and most frequently injured tendon is the Achilles tendon, which connects the calf muscle to the heelbone (calcaneus).  This is arguably the most important tendon around the ankle, as we use it for every step we take as well as running and jumping. Connecting one of the smaller calf muscles to the bottom of your foot is the posterior tibial tendon. This tendon helps to support the arch of your foot and is responsible for the ability to turn your foot to the inside. Also here are the anterior tibial tendon which helps you raise your foot, and the lateral malleolus and the peroneals, which help you turn your foot down or outward.

ankle tendons

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Muscles

The muscles of the lower leg are the primary movers of the ankle. They are the calf muscles which connect to the calcaneus (heelbone) by way of the Achilles tendon; the peroneals on the outside of the ankle (to bend the ankle down and out) , the posterior tibialis muscle (to support the arch and turn the foot inward), and the anterior tibialis muscle (to pull the ankle up).

Nerves
Nerves which feed the ankle are the same nerves which run down your leg and into your foot.  The tibial nerve is the most important, running past the medial malleolus (the malleolus is the bony prominence on each side of the ankle) and ending in the bottom of your foot.  The nerves on the front and outer edge of the ankle control the muscles in this area, and they give sensation to the top and outside edge of the foot.
nerves of ankle
Blood Vessels

Just as with the nerves that feed your ankle, the blood vessels run down the leg and end in the foot. The primary vessel is the dorsalis pedis and runs in front of your ankle, across the top of your foot. The next largest artery, called the posterior tibial artery, runs behind the medial malleolus, and send smaller vessels to your ankle joint. Additional, smaller arteries also supply the ankle.

blood vessels in foot and ankle

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Your ankle is a finely tuned instrument of interconnected, dependent parts, all of which must be in good working condition in order to walk, run, and jump. From this you can see how even a minor sprain could throw this system into disarray. Take care of your ankles and when you suspect an injury, don’t hesitate to contact PA Foot and Ankle Associates for a diagnosis and evaluation.

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