Functional Anatomy, Pathomechanics, and Pathophysiology of Lateral Ankle Instability

Abstract

OBJECTIVE: To describe the functional anatomy of the ankle complex as it relates to lateral ankle instability and to describe the pathomechanics and pathophysiology of acute lateral ankle sprains and chronic ankle instability. DATA SOURCES: I searched MEDLINE (1985-2001) and CINAHL (1982-2001) using the key words ankle sprain and ankle instability. DATA SYNTHESIS: Lateral ankle sprains are among the most common injuries incurred during sports participation. The ankle functions as a complex with contributions from the talocrural, subtalar, and inferior tibiofibular joints. Each of these joints must be considered in the pathomechanics and pathophysiology of lateral ankle sprains and chronic ankle instability. Lateral ankle sprains typically occur when the rearfoot undergoes excessive supination on an externally rotated lower leg. Recurrent ankle sprain is extremely common; in fact, the most common predisposition to suffering a sprain is the history of having suffered a previous ankle sprain. Chronic ankle instability may be due to mechanical instability, functional instability, or most likely, a combination of these 2 phenomena. Mechanical instability may be due to specific insufficiencies such as pathologic laxity, arthrokinematic changes, synovial irritation, or degenerative changes. Functional instability is caused by insufficiencies in proprioception and neuromuscular control. CONCLUSIONS/RECOMMENDATIONS: Lateral ankle sprains are often inadequately treated, resulting in frequent recurrence of ankle sprains. Appreciation of the complex anatomy and mechanics of the ankle joint and the pathomechanics and pathophysiology related to acute and chronic ankle instability is integral to the process of effectively evaluating and treating ankle injuries.

Figures

Figure 1

The talocrural axis of rotation.

Figure 2

The subtalar axis of rotation allows the triplanar motions of pronation and supination. This picture illustrates these motions in the open kinetic chain.

Figure 3

The intrinsic subtalar ligaments: (1) interosseous ligament, (2) cervical ligament, and (3) deep fibers of the extensor retinaculum. Reprinted with permission of Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc. 1999;31:1501–1508; Lippincott Williams & Wilkins.

Figure 4

The lateral ligaments of the ankle: (1) anterior talofibular ligament, (2) calcaneofibular ligament, (3) posterior talofibular ligament, (4) cervical ligament, and (5) lateral talocalcaneal ligament. Reprinted with permission of Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc. 1999;31:1501–1508; Lippincott Williams & Wilkins.

Figure 5

Paradigm of mechanical and functional insufficiencies that contribute to chronic ankle instability.

Figure 6

The medial subtalar glide test is performed by translating the calcaneus medially in the transverse plane. Reprinted with permission of Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc. 1999;31:1501–1508; Lippincott Williams & Wilkins.

Figure 7

Paradigm of proprioception and neuromuscular control. CNS indicates central nervous system.