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Ankle Anatomy and Biomechanics
Introduction
The ankle joint is composed of bones, ligaments, and tendons that provide an inherent balance between structure and function. Ligamentous structures connect the bones of the ankle to create a strong foundation for transmission of forces during weight-bearing activities. Traversing tendons work synergistically to create motion and generate power during ankle movement. Nerves and blood vessels provide sensation, proprioceptive feedback, and oxygen to all structures of the ankle. Each of these vital components work together biomechanically and play a critical role in the gait cycle. Understanding anatomy and biomechanics is important when evaluating and treating athletic injuries involving the ankle joint. In addition, gender-related differences including structure, kinematics, laxity, and neuromuscular control should also be addressed when managing injuries in the female athlete. This chapter will review the ankle bony, soft tissue, and neurovascular anatomy; the biomechanics underlying the gait cycle; and gender-related differences within the ankle joint.
Bony Anatomy
The distal tibia, distal fibula, and talus articulate to form the bony structure of the ankle joint. The distal tibial articular surface, also known as the tibial plafond, is a quadrilateral surface that is wider anteriorly. This surface is concave in the sagittal plane and slightly convex in the transverse plane. This allows smooth articulation with the dorsal surface of the talus, also called the trochlea, which is convex in the sagittal plane and approximately 4 mm wider anteriorly. , The distal end of the tibia has an inferomedial projection, the medial malleolus, which articulates with the medial articular surface of the talus during ankle motion. The distal aspect of the medial malleolus has two rounded projections, the anterior colliculus and the posterior colliculus. The anterior colliculus projects more distally. The distal, lateral tibia contains a notch for the fibula, also known as the incisura fibularis, and is surrounded by strong ligaments that make up the ankle syndesmosis, which will be discussed later. The distal aspect of the fibula projects past the tibial plafond and is referred to as the lateral malleolus. The medial aspect of the lateral malleolus articulates with the lateral surface of the talus. The tibial plafond, medial malleolus, and lateral malleolus together are known as the ankle mortise. With an intact syndesmosis, the ankle mortise acts to contain the talus and prevent its medial and lateral translation. The concavity of the tibial plafond in the sagittal plane creates a posterior, distal protrusion known as the posterior malleolus. This structure differs from the medial and lateral malleoli by not providing a vertical bony wall to prevent talar translation.
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