Ankle Ligaments & Their Functions

Medically Reviewed By : Dr Sravya, MBBS, MS

Introduction

To discuss the pathomechanics and pathophysiology of severe sprains of the lateral ankle and long-term ankle instability, as well as the physiological anatomy of the ankle as it pertains to lateral ankle instability.

A collection of ligaments that are vital in tying the bones together and offering support for the ankle joint.

These ligaments include:

Anterior Talofibular Ligament (ATFL): Situated in front of the lateral malleolus (the bony bump on the outside of the ankle), the ATFL extends to the talus bone.Its main purpose is to stop the foot from moving too far forward.
Posterior Talofibular Ligament (PTFL): Positioned at the back of the lateral malleolus, the PTFL connects to the talus bone. Its main role is to provide stability against excessive backward movement of the foot.
Calcaneofibular Ligament (CFL): Running from the lateral malleolus to the calcaneus (heel bone), the CFL contributes additional lateral stability to the ankle.
Deltoid Ligament: Found on the medial (inner) side of the ankle, the deltoid ligament is a robust, triangular-shaped ligament that connects the tibia to the talus and calcaneus bones. Its function is to support the ankle and prevent excessive inward rolling (inversion) of the foot.

These ligaments are vital for maintaining ankle joint stability and preventing injuries during activities like walking, running, and jumping. Injuries to these ligaments can vary from mild sprains to more severe tears. Proper care and rehabilitation are crucial for recovering from ankle ligament injuries. If there is a suspicion of an ankle injury, seeking advice from a medical professional is recommended for accurate diagnosis and appropriate treatment.

In This Article

Functional Anatomy

The distal tibiofibular syndesmosis, the subtalar joint, and the talocrural joint make up the ankle complex. Together, these three joints enable the rearfoot to move in unison. Rearfoot motion is frequently described as taking place in the following three cardinal planes:

Rearfoot movement, however, does not take place in isolation in each of the different planes; rather, the rearfoot can move as a unit around an axis of rotation that is perpendicular to the long axis of the lower leg thanks to the coordinated movement of the three joints.
Due to the oblique axis of rotation of the talocrural and subtalar joints, rearfoot movements do not always take place in the cardinal planes.
Pronation and supination are the finest terms to describe coupled rearfoot action. Pronation involves dorsiflexion, eversion, and external rotation in the open kinetic chain, whereas supination involves plantar flexion, inversion, and internal rotation. Pronation is made up of plantar flexion, eversion, and external rotation in the closed kinetic chain, whereas supination is made up of dorsiflexion, inversion, and internal rotation.
The congruity of the articular surfaces under load, static ligamentous constraints, and musculotendinous units, which enable dynamic stabilization of the joints, are the three main factors that contribute to the stability of the ankle joints. Later on, we'll talk about how each of these functions about lateral ankle instability.

Talocrural Joint Anatomy

The medial malleolus, the tibial plafond, the lateral malleolus, and the dome of the talus come together to create the talocrural, or tibiotalar, joint. During weight bearing, torque may be transferred from the lower leg (internal and external rotation) to the foot (pronation and supination) thanks to the configuration of the talocrural joint. When considered alone, this joint—sometimes referred to as the “mortise” joint—can be seen as a hinge joint that permits plantar flexion and dorsiflexion.

The medial and lateral malleoli are where the talocrural joint's axis of rotation crosses through.
When it goes through the tibia, it is somewhat anterior to the frontal plane; however, when it passes through the fibula, it is slightly posterior to the frontal plane.
The talocrural joint moves alone, mostly in the sagittal plane, although there is also very little frontal and transverse motion at the oblique axis of rotation. Although the ligaments play a critical role in the stability of the talocrural joint, the articular surfaces of the ankle complex act as the main stabilizers against excessive talar rotation and translation when the ankle complex is completely loaded.

The anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL), calcaneofibular ligament (CFL), and deltoid ligament all provide ligamentous support for the talocrural joint. The medial aspect of the ankle is supported by the deltoid ligament, with lateral support provided by the ATFL, PTFL, and CFL.

The ATFL runs from the lateral malleolus anteriorly and medially towards the talus on the dorsolateral side of the foot at an angle of about 45 degrees from the frontal plane.
The ATFL is typically 24.8 mm long and 7.2 mm broad. According to in vitro kinematic tests, the ATFL inhibits excessive internal and external rotation of the talus on the tibia, as well as anterior displacement of the talus from the mortise.
As the ankle bends into plantar flexion, the tension on the ATFL rises. In comparison to the PTFL, CFL, anterior inferior tibiofibular ligament, and deltoid ligament, the ATFL exhibits lower maximum load and energy to failure values under tensile stress.

At a typical angle of 133° from the long axis of the fibula, the CFL runs from the lateral malleolus posteriorly and inferiorly to the lateral face of the calcaneus. The talocrural and subtalar joints’ excessive supination is limited by the CFL. The CFL limits excessive rearfoot inversion and internal rotation, and in vitro, tests have shown that it is tautest when the ankle is dorsiflexed. The second most often damaged of the lateral talocrural ligaments is the CFL.

The PTFL extends posteriorly from the lateral malleolus to the posterolateral side of the talus. The loaded talocrural joint is restrained against inversion and internal rotation by the PTFL, which has large insertions on the talus and fibula.

Subtalar Joint Anatomy

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Similar to the talocrural joint, the subtalar joint is made up of the articulations between the talus and the calcaneus and translates torque between the foot's pronation and supination and the lower leg's internal and exterior rotation.
The subtalar joint, which has a complex anatomy and two distinct joint cavities, permits pronation and supination actions.
The superior posterior facet of the calcaneus and the inferior posterior facet of the talus combine to produce the posterior subtalar joint.
The sustentacular tali of the calcaneus, the anterior-superior facets, the head of the talus, and the concave proximal surface of the tarsal navicular combine to create the anterior subtalar, or talocalcaneonavicular, joint.
The talar head serves as the ball in this articulation, while the anterior calcaneal and proximal navicular surfaces, along with the spring ligament, serve as the socket. The anterior subtalar joint's anatomy showed significant individual heterogeneity, according to Viladot et al.
The sinus tarsi and canalis tarsi divide the anterior and posterior subtalar joints, which each contain a unique ligamentous joint capsule. The anterior and posterior joints share the same axis of rotation, despite the anterior joint's more medial location and higher centre of rotation.
The subtalar joint's oblique axis of rotation, which averages a 42° upward tilt as well as a 23° medial angulation concerning the perpendicular planes of the foot, was the result of this difference. The location of the axis of rotation varies significantly across people.

It is unclear how extensively the subtalar joint is supported by ligaments. There are significant differences in the vocabulary used to describe each specific ligament and the roles that these ligaments play in the literature. The lateral ligaments can essentially be classified into three groups: Deep ligaments, peripheral ligaments, and retinacula are listed in that order.

The cervical and interosseous ligaments are part of the deep ligaments.
These ligaments work as a barrier within the anterior and posterior joint capsules, stabilising the subtalar joint.
These ligaments, which obliquely cross over the canalis tarsi, are often referred to as the "cruciate ligaments of the subtalar joint."
The cervical ligament extends through the cervical tubercle of the calcaneus anteriorly and medially to the talar neck, lying anterior and lateral to the interosseous ligament.
The cervical ligament supports both the anterior and posterior joints and is located within the sinus tarsi. It is the strongest of the subtalar ligaments, and in vitro, kinematic studies have demonstrated that it can withstand supination.

The CFL, lateral talocalcaneal (LTCL), and tibiotalocalcaneal (FTCL) ligaments are among the subtalar joint’s periphery ligaments. The CFL plays a crucial role in limiting the calcaneus’ excessive internal rotation and inversion concerning the talus. Although the CFL generally does not join the calcaneus to the talus, there have been reports of unusual CFL attachments to the talus.

Lateral Ankle Ligaments

The LTCL only crosses the posterior subtalar joint while running anteriorly and parallel with the CFL. This LTCL has been described in a variety of forms, and occasionally its fibres are continuous with those of the CFL. The FTCL, also known as the ligament of Rouviere, extends along the lateral malleolus’ posterior side through the talus’ posterolateral surface, where it meets the posterolateral calcaneus. It aids in preventing over-supination and is posterior to the CFL.

An additional static supporter of the lateral ankle complex is the bifurcate ligament. It has two branches: the dorsal calcaneonavicular and the dorsal calcaneocuboid. This ligament prevents the midfoot from supinating; therefore, lateral ankle sprains frequently involve hyper supination mechanisms in addition to this injury.

Mechanical Instability

Anatomical alterations following an initial ankle sprain result in insufficiencies that predispose the ankle to subsequent episodes of instability, which causes mechanical instability of the ankle complex. Pathologic laxity, poor arthrokinematics, synovial alterations, and the onset of degenerative joint disease are some of these modifications that may take place simultaneously or separately.

Synovial and Degenerative Changes

The development of degenerative joint lesions or insufficiencies brought on by synovial enlargement and impingement may potentially result in mechanical instability inside the ankle complex. Between the posterior subtalar joint capsule and the talocrural joint capsule, synovial inflammation has been seen. The impingement of hypertrophied synovial tissue within several bones of the ankle complex causes frequent bouts of discomfort and recurring ankle instability in patients, along with synovial inflammation.

Functional instability

The neuromuscular system that gives the ankle its dynamic support undergoes negative modifications as a result of injury to the lateral ligaments of the ankle. In 1965, Freeman et al. (16, 17) introduced the idea of functional instability.

They concluded that damaged articular mechanoreceptors in the lateral ankle ligaments caused proprioceptive impairments, which led to decreased balance in those with lateral ankle sprains. Even if it is significant, the role that decreased proprioception plays in ankle-ligament damage predisposes athletes to functional ankle instability. Impaired neuromuscular control must be accounted for in the pathoetiologic model for the dynamic defense mechanism to be effective against hyper supination within the rearfoot.

Conclusion:

Lateral ankle sprains are frequently not properly treated, which causes them to recur frequently. Effectively assessing and treating ankle injuries depends on an understanding of the complex structure and mechanics of the ankle joint as well as the pathomechanics and pathophysiology associated with chronic and acute ankle instability.

Although lateral ankle sprains are among the most frequent injuries experienced by physically active individuals, clinical treatment approaches seem to be insufficient for avoiding the recurrence of these injuries.
The pathomechanics of lateral ankle sprains and CAI can be better understood by studying the anatomy and mechanics of the rearfoot complex.
The particular insufficiencies of pathologic laxity, arthrokinematic limitations, synovial irritation, or degenerative alterations to the ankle complex's joints may all contribute to the mechanical instability of the ankle.
Insufficiencies in proprioception, neuromuscular control, postural control, and strength are the main causes of functional instability. Identification of the signs of both mechanical and functional instabilities should be a part of the clinical care of individuals with unstable ankles.
The goal of treatment will be to address certain insufficiencies once they have been recognised, with a particular emphasis on lowering the risk of recurring ankle sprains.

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