The ankle is the joint that connects the lower leg to the foot. The joint is essential for walking and all mobility. The ankle is a commonly injured joint with the most common injury being an ankle sprain. The ankle joint has a lot of flexibility which is useful for the way we move around, but makes it more at risk for injury as well.
The ankle joint is a hinge joint, which means that movement occurs in one plane. This movement includes dorsiflexion and plantarflexion. Dorsiflexion is when your toes come up towards your shin and plantar flexion is when your toes point down towards the ground. Although the ankle joint is a hinge joint, there is a joint called the subtalar joint in the foot that also allows for eversion and inversion movements as well. Eversion is when the foot rotates outward and inversion is when the foot rotates inward.
There are four bones in the ankle and foot that allow for movement in multiple directions. These include the bones in the lower leg – the tibia (shin bone) and the fibula (smaller bone on the outside of lower leg). In the foot, there are also the talus and calcaneus which contribute to ankle motion. The talus sits between the tibia and fibula and the calcaneus is the heel bone in the foot. These bones come together to form 3 separate joints in the ankle and foot: the distal tibiofibular joint, the talocrural joint, and subtalar joint. The distal tibiofibular joint includes the distal (or bottom) part of both the tibia and fibula.
The talocrural joint is the true ankle joint. This is the hinge joint that was referenced above that allows for dorsiflexion and plantarflexion or moving the ankle up and down. The subtalar joint as mentioned before allows for movement of the foot and ankle in and out which is called inversion and eversion. The distal tibiofibular joint is called a syndesmotic joint and does not allow for much movement. This joint has several ligaments around it and is there to stabilize the ankle as much as possible. This is the joint that is injured in what is referred to as a high ankle sprain. In a regular ankle sprain, it is typically the ligaments, tendons, and muscles that are injured. Ligaments are connective tissue that connect from bone to bone and tendons are connective tissue that connect from muscle to bone.
There are several ligaments in the ankle joint that help to stabilize the joint. These include the anterior talofibular ligament, the posterior talofibular ligament, the calcaneofibular ligament, and the deltoid ligament. The deltoid ligament reinforces the medial (inside) aspect of the ankle while the other three ligaments help to reinforce the lateral (outside) aspect of the ankle. Ligaments are commonly injured in ankle sprains. When the ligaments have been overstretched and damaged, balance becomes difficult. This is because the ligaments provide feedback to the brain about where the foot
The muscles in and around the ankle are in three different quadrants: anterior, posterior, and lateral – which just means the front, back, and outside of the ankle. In the anterior or front quadrant, there is a muscle named anterior tibialis. This muscle helps to bring your toes up towards your shin. This muscle is the one involved in shin splints when the pain is in the front of the leg on the outside of the shin bone. There are also muscles named extensor hallucis longus and extensor digitorum longus that cross the ankle and attach to the foot. These muscles also help some to bring the toes up to the shin, but also help to bring the toes up towards the shin as well. In the lateral or outside quadrant, there are the two peroneal muscles, also called the fibularis muscles, named fibularis longus and fibularis brevis. They help the foot move into eversion, which is when the foot rotates out to the side. These muscles also help slightly with plantarflexion, or pointing the toes down. The posterior or back quadrant include the two calf muscles, gastrocnemius and soleus, flexor hallucis longus, flexor digitorum longus, and posterior tibialis. The flexor hallucis longus and flexor digitorum longus muscles do the opposite of the extensor versions of these muscles, so instead of bringing the toes up they help to bend or curl the toes. Posterior tibialis helps to invert the ankle, or to rotate it in towards the other leg. The calf muscles are the muscles that help to point your toes or to help you stand on your toes. The two calf muscles come all the way down the lower leg and become the Achilles tendon, which crosses the ankle. If the Achilles tendon is fully torn you lose the function of the calf muscles as well since the tendon is how they are able to move the ankle.
There are nerves that help to turn on the muscles around the ankle and also help with the ability to feel around the lower leg and ankle. This starts with the sciatic nerve that originates in the back and divides into different nerves as it moves down the leg. These smaller nerves include the tibial nerve, sural nerve, common fibular nerve, superficial fibular nerve, and the deep fibular nerve. The tibial nerve turns on the muscles in the posterior or back compartment of the lower leg and ankle, including the calf muscles. The sural nerve provides feeling to the backside and outside aspects of the lower leg and foot. The common fibular nerve provides feeling to the outside of the back of the leg. The superficial fibular nerve provides feeling to the outside of the front of the shin and top of the foot. It also turns on the fibularis and fibularis brevis muscles. Finally, the deep fibular nerve turns on the muscles in the anterior or front compartment of the ankle. This is the muscle that is associated with a condition called drop foot which is when you are unable to bring your toes up which affects walking. Because these muscles are divisions of the sciatic nerve, this is why a back injury can cause issues down the leg even into the foot and ankle. These issues can include both sensory or feeling changes like numbness, tingling, or burning as well as motor or muscle changes like weakness.
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