Chapter 14: Radiologic Evaluation of the Ankle and Foot

Introduction

Injuries to the ankle and foot occur with great frequency. The ankle is considered the most commonly injured, major weight-bearing joint in the body. However, the true incidence of such injuries is unknown, because a variety of clinicians treat ankle injuries and their definitions are often imprecise. Most ankle injuries are straightforward ligamentous injuries. However, the clinical presentation of subtle ankle and foot fractures can be similar to that of ankle sprains, and these fractures can be missed on initial examination. Appropriate imaging can minimize delays in treatment that may result in long-term disability and surgery.

Review of Anatomy

Osseous Anatomy

Ankle

The ankle joint is formed by the articulation of the distal tibia and fibula with the talus (Fig. 14-1).^1–9 The distal end of the tibia is distinguished by a broad articular surface, the tibial plafond; an elongated medial process, the medial malleolus; an expanded process at the anteromedial aspect, the anterior tubercle; and a posterior marginal rim, sometimes called the third malleolus or posterior malleolus. The distal end of the fibula, the lateral malleolus, is slightly posterior to and reaches below the level of the medial malleolus, extending alongside the talus. The inferior contours of the distal tibia and fibula combine to form a deep socket, or ankle mortise, into which the upper end of the talus fits. This articulation is the talocrural joint, or ankle joint proper.

Foot

The foot consists of 26 bones. There are 7 tarsals, 5 metatarsals, and 14 phalanges (Fig. 14-2).

Tarsals

The tarsals include the talus, calcaneus, cuboid, navicular, and three cuneiforms.

The talus is the second largest tarsal and is key in transmitting weight-bearing forces from the lower leg to the foot. The body of the talus articulates in the talocrural joint. The superior surface of the body is referred to as the talar dome. The talar neck lies anterior to the body. The talar head articulates with the navicular anteriorly and the calcaneus inferiorly. The posterior articulation between the talus and calcaneus is the subtalar joint. The anterior articulation between the talus and calcaneus is part of the talocalcaneonavicular joint, the complex articulation, surrounded by one capsule, between the talus, navicular, and upper surface of the plantar calcaneonavicular ligament.

The calcaneus is the largest tarsal bone. The posteroinferior aspect is the tuberosity or heel. A medial process and larger ...