Transverse Tarsal Joint (Talonavicular Joint and Calcaneocuboid Joint)
The transverse tarsal joint, also known as the midtarsal joint, anatomically consists of two distinct and independent joints. These are the talonavicular joint and the calcaneocuboid joint, which together play a crucial role in organically connecting the rearfoot and the midfoot.The talocrural (ankle) joint primarily allows simple movements in the sagittal plane, namely dorsiflexion and plantarflexion. In contrast, the subtalar joint enables more complex oblique movements, consisting of two primary motion components: inversion and eversion, as well as abduction and adduction.
The transverse tarsal joint facilitates motion along a unique oblique axis that nearly equally traverses all three primary planes of movement. A particularly noteworthy function of this joint is its ability to execute intricate pronation and supination motion patterns, allowing the foot to adapt effectively to various terrain surfaces during weight-bearing activities.
The transverse tarsal joint forms a closely integrated and dynamic functional relationship with the subtalar joint. These two joints work in a complementary and cooperative manner to finely adjust most of the foot's pronation and supination positions.
Structure and Ligaments of the Talonavicular Joint
The talonavicular joint (part of the medial compartment of the transverse tarsal joint) is a sophisticated ball-and-socket joint that provides critical mobility along the medial (longitudinal) arch of the foot. This mobility is primarily expressed as complex torsional movements of the midfoot relative to the rearfoot (inversion and eversion), playing a vital role in walking and posture control.Anatomically, the talonavicular joint is formed between the smoothly convex head of the talus and the concave surfaces of the navicular bone and the proximal surface of the "spring" ligament. The distinctive convex-concave structural relationship of this joint is illustrated in detail in diagrams.
The spring ligament is a robust band of connective tissue composed of thick and broad collagen fibers. It spans from the sustentaculum tali of the calcaneus to the plantar-medial surface of the navicular bone, forming a crucial anatomical bridge.
This ligament plays a key role by directly supporting the medial and plantar convex surfaces of the talar head, thereby forming the essential "floor and medial wall" of the talonavicular joint. Particularly in a standing posture, where body weight places significant pressure on the talar head in a downward and medially-directed manner, a strong support structure in this area is indispensable.
One notable anatomical feature is that the medial surface of the spring ligament, which contacts the talar head directly, is covered with specialized fibrocartilage. This allows smooth joint movement. It is important to note that the official anatomical name of the spring ligament is the plantar calcaneonavicular ligament. Due to its rich collagen composition, the ligament exhibits high durability and resistance to stretching.
The entire talonavicular joint is encased in a complex and irregularly shaped joint capsule. The functional stability of this capsule is further enhanced by various reinforcing ligaments. The detailed structures and functions of these reinforcing ligaments are systematically summarized in the box on the preceding page.