The joints, ligaments, and muscles of the ankle and foot provide stability and mobility in the terminal structures of the lower extremity. During standing, the foot bears the weight of the body with minimum muscle energy expenditure. The foot must also be both pliable and relatively rigid depending on various functional demands. This versatility allows the foot to absorb forces, accommodate to uneven surfaces, and serve as a structural lever to propel the body forward during walking and running.
A clear understanding of the complex anatomy and kinesiology of the ankle and foot is important when treating impairment in this region of the body. The first section of this chapter reviews highlights of these areas the reader should know and understand. The second section contains guidelines for the management of disorders and surgeries in the foot and ankle region, and the third section describes exercise interventions for this region. Chapters 10, 11, 12, 13 present general information on principles of management; the reader should be familiar with the material in these chapters and should have a background in examination and evaluation in order to effectively design a therapeutic exercise program to improve ankle and foot function in patients with impairments from injury, pathology, or recovery following surgery.
Structure and Function of the Ankle and Foot
The bones of the ankle and foot consist of the distal tibia and fibula, 7 tarsals, 5 metatarsals, and 14 phalanges (Fig. 22.1).
Bones of the ankle and foot. (A) Anterior view of the lower leg and ankle, (B) medial and (C) lateral views of the ankle and foot.
Structural Relationships and Motions
The leg is structurally adapted to transmit ground reaction forces from the foot upward to the knee joint and femur during upright activities. Depending on the activity, the foot and ankle provide a foundation of either stability or motion to the distal extremity that assists the leg in managing forces and demands. The motions in the ankle and foot are defined using primary plane and triplanar descriptors.
The tibia and fibula make up the leg. These two bones are bound together by an interosseous membrane between the bones, strong anterior and posterior inferior tibiofibular ligaments that hold the distal tibiofibular articulation together, and a strong capsule that encloses the proximal tibiofibular articulation. Unlike the radius and ulna in the upper extremity, the tibia and fibula do not rotate around each other, but there is slight movement between the two bones that allows greater ankle joint motion.
The foot is divided into three segments: hindfoot, midfoot, and forefoot.