Ankle Anatomy

Although it is typically referred to as a single joint, the ankle is actually two joints:

The true ankle joint , which is composed of three bones:

• the tibia , the larger and stronger of the two lower leg bones, which forms the inside part of the of the ankle
• the fibula , the smaller bone of the lower leg, which forms the outside part of the ankle
• the talus , a small bone between the tibia and fibula and the calcaneus, or heel bone.

The subtalar joint , which is composed of two bones:

• the talus
• the calcaneus

The ends of the bones are covered by articular cartilage. The space in the joint is lined with a thin membrane called the synovium, which cushions the joint and secretes a lubricating fluid, called synovial fluid.

Several strong bands of connective tissue, called ligaments, hold the bones of the ankles together. They include the following:

• anterior tibiofibular ligament , which connects the tibia to the fibula.
• lateral collateral ligaments , which connect the fibula to the calcaneus and provide stability to the outsides of the ankles.
• deltoid ligaments , which attach the tibia to the talus and calcaneus and provide stability to the insides of the ankles.

A number of tendons run through the ankle, attaching muscles of the lower leg to the bones of the foot and ankle. The major tendons include the following:

• Achilles tendon , which attaches the calf muscle and calcaneus.
• flexor hallicus longus , which runs along the inside of the ankle and attaches to the big toe.
• flexor digitorum , which runs along the inside of the ankle and attaches to the other toes.
• peroneal tendons , a set of three tendons which run along the outside of the ankle and attach at the 5th metatarsal (the shaft of the small toe) and the bottom of the foot.
• posterior tibialis tendon , which attaches at the mid-foot and helps maintain the foot's arch.
• anterior tibialis tendon , which runs down the front of the leg and attaches to the bones of the midfoot. These tendons pull the foot toward the body and help control their motion.