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©William E. Prentice


When you finish this chapter you will be able to:

  • Describe the bony, ligamentous, and muscular anatomy of the ankle and lower leg.

  • List considerations for preventing injuries to the ankle and lower leg.

  • Explain how to assess common ankle and lower-leg injuries.

  • Identify the possible causes and signs of various injuries that can occur in the ankle and lower leg.

  • Examine the procedures that can be used in caring for ankle and lower leg injuries.



The portion of the anatomy below the knee and above the ankle is the lower leg. It is composed of the thicker tibia, which is more medial, and the thinner fibula, which is more lateral. The ankle joint or talocrural joint is formed by the thickened distal portion of the fibula, called the lateral malleolus; the thickened distal portion of the tibia, called the medial malleolus; and the more-or-less cube-shaped tarsal bone, called the talus, that fits between the two malleoli. The ankle joint allows two motions: plantarflexion and dorsiflexion. The joint between the talus and the calcaneus is called the subtalar joint. Inversion and eversion take place at the subtalar joint (Figure 15–1).


The ankle joint is formed by the tibia, fibula, and talus. The subtalar joint is formed by the talus and calcaneus. ©William E. Prentice

The ankle joint is composed of the

  • Tibia

  • Fibula

  • Talus


The tibia and fibula are held together by the interosseous membrane, which extends the entire length of the two bones (Figure 15–1). The anterior and posterior tibiofibular ligaments bridge the tibia and fibula and form the distal portion of the interosseous membrane (Figure 15–2A). The medial aspect of the ankle is relatively stable because of the thick deltoid ligament. The presence of this strong deltoid ligament, combined with the fact that the lateral malleolus of the fibula extends further distally than the medial malleolus, limits the ability of the ankle to evert (Figure 15–2B). Thus, eversion ankle sprains are considerably less common than inversion sprains. The three lateral ligaments include the anterior talofibular, the posterior talofibular, and the calcaneofibular. The lateral ligaments collectively limit inversion and are much more susceptible to injury.


Ligaments of the ankle joint: (A) Lateral view. (B) Medial view. (From Van De Graaff, K., Human anatomy, 6th ed. Dubuque, IA: McGraw-Hill Higher Education, 2009.)

The talocrural joint allows two motions:

  • Plantarflexion

  • Dorsiflexion

The subtalar joint allows two motions:

  • Inversion

  • Eversion



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