Ligaments of the Subtalar Joint

Ligaments of the Subtalar Joint

The complex structure of the subtalar joint is intricately supported by multiple layers of ligament systems. The posterior and anterior-middle joints are surrounded by independent joint capsules, and this anatomical separation enables the joint's specialized functions. Notably, the larger posterior joint capsule is further reinforced by three intricate ligamentous structures: the medial talocalcaneal ligament, posterior talocalcaneal ligament, and lateral talocalcaneal ligament.

These ligaments are structurally fused with the joint capsule in most cases, making them difficult to distinguish visually. They play an important role as secondary stabilizers of the joint. The primary stability of the joint, however, is provided by other crucial ligamentous structures. Among them, the calcaneofibular ligament effectively restricts excessive inversion movements, while the deltoid ligament (tibionavicular fibers) prevents excessive eversion.

The interosseous (talocalcaneal) ligament and cervical ligament, due to their unique anatomical positions connecting the talus and calcaneus directly, are the most critical structures for the non-muscular stability of the subtalar joint.

These two ligaments have a broad, flat structure and exhibit a distinctive oblique orientation within the tarsal sinus. Because of their anatomical location, they are difficult to observe visually without directly exposing the joint. Specifically, the interosseous talocalcaneal ligament is composed of clearly distinguishable anterior and posterior fibers. These fibers originate from the calcaneal sulcus, travel upward, and attach to the talar sulcus and surrounding areas, forming a complex trajectory.

The cervical ligament is larger than the interosseous ligament and exhibits a similar oblique fiber structure. However, it is positioned more laterally within the calcaneal sulcus and has a unique attachment point. From this attachment, the cervical ligament travels upward and medially, primarily attaching to the inferior-lateral portion of the talar neck (which gives it the name "cervical" ligament). Due to these structural characteristics, the cervical ligament, together with the interosseous ligament, functions to effectively limit all joint motions, particularly at the terminal range of inversion.

Although these ligaments within the tarsal sinus are widely recognized as the primary stabilizing structures of the subtalar joint, much remains unclear about their precise anatomical structures and comprehensive functional roles.