The bony landmarks that represent the ankles are actually the ends of the two lower leg bones, the tibia and the fibula. The bony protrusions are called the medial and lateral malleolus. The medial malleolus is the end of the tibia, which sits on the inside of the foot. The lateral malleolus is the end of the fibula, which sits on the outside of the foot.

The ankle actually consists of all the tarsal bones. (These seven bones were discussed earlier.) The talus is considered the real anklebone and is the initial weight-bearing bone during the action of walking.

Joints

Another area of importance in dealing with the ankle is the joint involved with the movement of this area. A joint is a point of contact between bones. There are different classifications for joints depending upon structure or function.

Structural classification depends upon the presence or absence of space between the bones that are touching. The joints you are dealing with have a cavity, known as a synovial cavity, between the touching bones. This classifies these joints as synovial joints.

Functional classification deals with the degree of movement the joint allows. A diarthrosis is a freely movable joint, which is the type of joint you are involved with at this time. These joints have a variety of shapes and allow a range of movement. They are covered with a protective cartilage that allows for freer movement and provides shock absorption.

The ankle joint is also known as the talocrural joint. It is between the end of the malleoli and the talus. This joint is classified structurally as a hinge joint. Part of the classification stipulates that the surface of one bone fits into the surface of another bone, which does happen in the ankles. The movement of the joint is like a door on a hinge; in anatomy this movement is generally flexion and extension. When you flex a joint, it is as though you pull the door in; when you extend, you open the door.

Special Movements

The synovial joints have a subgroup known as special movements. These movements are part of the biomechanics of the feet. Every time you walk, you perform these special movements. Six of these special movements deal specifically with the feet and hands:

• Inversion moves the soles inward, so they face each other.

• Eversion moves the soles away, so they face away from each other.

• Dorsiflexion bends the foot up.

• Plantar flexion bends the foot down.

• Abduction moves the foot away from the center of the body.

• Adduction also moves the foot toward the center of the body.

Although not special movements, there are two others that are key to some of these movements: supination is a three-point movement of inversion, plantar flexion, and adduction; and pronation is a three-point movement of eversion, dorsiflexion, and abduction.