Ankle – Bones, Ligaments, Muscles & Conditions
The ankle is one of the most versatile joint complexes in the body. It is built for weight bearing, mobility, adaptability and stability. The foot and ankle allow us to walk, stand and serve as our connection to the ground. The ankle must be able to withstand the stress of body weight, and also be able to adapt to, and react quickly to changes in environment and walking surface.
Bone and Joint
The ankle is made up of two joints, the inferior talocrural joint and the subtalar joint.
The inferior tibiofibular joint is located between the large bone of the lower leg (tibia) and the smaller fibula, which then attach to the talus bone of the foot to form the talocrural joint. The talocrural joint is sometimes called the true ankle joint and is responsible for dorsiflexion and plantar flexion (up and down) movement of the foot. The joint between the tibia and talus bears the most of our body weight.
Beneath the talocrural joint is the subtalar joint. The subtalar joint is located between the talus bone and calcaneus or heel bone. This joint is responsible for ankle inversion (turning in) and eversion (turning out).
Running between the tibia and fibula is a fibrous membrane called the interosseous membrane. This membrane joins the tibia and fibula all the way up the lower leg, extending toward the knee. At the upper end, near the outside of the knee, is the superior tibiofibular joint.
Any restriction or dysfunction of these joints can produce symptoms in the ankle. The bony joint surfaces all have articular cartilage that covers the ends of the bones. The articular cartilage has a smooth and shiny surface, which allows the ends of the bones to slide freely over each other.
Common injuries of the bones of the ankle include ankle fracture, fracture of the lateral malleolus, trimalleolar fracture, ankle dislocation, ankle fracture dislocation, calcaneal fracture, osteoarthritis of the ankle, rheumatoid arthritis of the ankle.
Ligaments are fibrous, strong soft tissue structures that attach bone to bone. The primary job of ligaments is to allow for normal motion, provide stability and restrict excessive movement. The ligaments of the ankle are the primary stabilizers of the joint.
Four major ligaments hold together the ankle. The medial part of the ankle is supported by the strong and thick deltoid ligament, and runs from the medial malleolus of the tibia to the talus, calcaneus and navicular bone of the foot and ankle complex. On the lateral side of the ankle are three ligaments running from the lateral malleolus of the fibula. Two of these – the anterior talofibular ligament, and the posterior talofibular ligament- attach to the talus. The third calcaneofibular ligament attaches to the calcaneus, or heel bone.
These ligaments give the ankle lateral support and stability. The anterior talofibular ligament is the most commonly injured ligament in the body. Lateral ankle sprains account for 85% of all ankle sprains.
Common ankle ligament injuries include ankle sprain (Grades 1,2, and 3) lateral ankle sprain, ankle instability, ankle ligament tear, lateral ankle instability and anterior ankle instability.
The muscles that control ankle movement originate in the lower leg. They are responsible for foot and ankle movement up and down (dorsiflexion and plantar flexion) and turning in and out (inversion and eversion). The muscle bellies are located in the lower leg while the tendons travel and attach to the foot and ankle. Tendons are the part of the muscle that attaches the muscle to the bone.
In addition to movement, strong muscles provide active stability to the ankle as opposed to the passive stabilization of the ligaments. The major muscles of the ankle include the gastrocnemius and soleus (calf) muscles, which push the foot down and allow us to go up on our toes. These two large muscles join at the ankle to form the Achilles tendon.
The two peroneal muscles, longus and brevis, are located on the outside of the ankle, and push the foot down (plantar flexion) and turn it out (eversion). They also support the lateral ankle to prevent sprains. The posterior tibialis is located on the inside of the ankle, and supports the arch of the foot and helps turn the ankle in (inversion). The anterior tibialis muscle attaches to the front of the foot, and helps lift it up (dorsiflexion).
Any damage, weakness, tendonitis or tear of these muscles or tendons can have a profound effect on the function and stability of the foot and ankle. For instance, weakness of the anterior tibialis may produce a condition called foot drop. The result is a dragging of the foot producing a foot slap or tripping while walking.
Common muscle conditions include Achilles tendonitis, Achilles tendon rupture, posterior tibialis tendonitis, peroneal tendonitis, Drop foot, anterior tibialis weakness, Shin splints and anterior compartment syndrome.
A burse is a fluid filled sac that decreases friction between two tissues. Burse are commonly found near a joint, and act as lubricating structures between tendon and bone. There are several bursa in the foot and ankle region. The most common are the retrocalcaneal bursa, subcutaneous calcaneal bursa, and subcutaneous bursa of the medial malleolus.
The retrocalcaneal bursa is located between the Achilles tendon and calcaneus (heel) bone. Direct or repetitive trauma such as consistent rubbing or friction can produce bursitis in this area. The subcutaneous calcaneal bursa, also called the Achilles bursa, is lower down near the heel. The subcutaneous bursa of the medial malleolus is located below the edge of the medial malleolus. Tight athletic footwear can produce rubbing and bursitis in this area.
Some common conditions of the bursa include Achilles bursitis, retrocalcaneal bursitis, and bursitis of the medial malleolus.