Transverse tarsal joint

Articular surfaces

The talonavicular joint is an articulation between the head of talus and the proximal/posterior aspect of the navicular bone.

The navicular articular surface of the head of talus points distally or anteriorly. It is orientated inferiorly in the vertical plane and medially in the horizontal plane, having an overall inferomedial orientation. The navicular articular surface is ovoid and convex in the horizontal and vertical planes. The corresponding proximal articular surface of the navicular bone is oppositely shaped and has a concave and oval shape in the horizontal plane, pointing distally to meet the navicular articular surface.

The calcaneocuboid joint connects the anterior (distal) aspect of the calcaneus with the posterior (proximal) aspect of the cuboid.

The articular surface for cuboid located on the calcaneus has a quadrilateral shape and a concavo-convex, undulating surface. It is divided into superior and inferior parts, which have opposite orientations. The superior part is concave in the horizontal and vertical planes, while the inferior part is convex in the same planes. The articular surface of the cuboid has similar, but reciprocal structural characteristics; it is also quadrilateral and undulating, with a convex superior part and a concave inferior part. This matching and mirroring relationship creates a saddle type joint and a congruent fit between the articular surfaces, thus making this joint much less mobile compared to the talonavicular joint.

Joint capsule

The transverse tarsal joint is not considered a true anatomical joint due to the fact that it is not contained within one joint capsule. Instead, it is classified as a functional joint that consists of the aforementioned talonavicular and calcaneocuboid anatomical articulations. The talonavicular joint shares a joint capsule with the articulations formed by the anterior and middle calcaneal facets of the talus with their talar counterparts on the calcaneus; hence these three articulations are anatomically referred to as the talocalcaneonavicular joint. The joint capsule of the talocalcaneonavicular joint is weak on all sides, except the posteroinferior border which is shared with the anterior part of the capsule of the talocalcaneal/subtalar joint.

The calcanecuboid joint is exclusively confined to its joint capsule, which encloses the joint on all sides. Its superior and inferior borders are thickened by ligaments which will be discussed below.

Both joint capsules are lined internally with synovial membrane, which secretes viscous synovial fluid that acts as a lubricant. The membrane extends until the margins of the respective articular surfaces, while the latter are lined by hyaline cartilage.

Learn more about the general features of the synovial joints by exploring articles, diagrams, videos and quizzes.

Ligaments

Innervation

The talonavicular joint receives innervation from two sources:

• Deep fibular nerve, which stems directly from the sciatic nerve
• Medial plantar nerve, which originates from the tibial nerve

In turn, the calcaneocuboid joint receives innervation from three sources:

• Deep fibular nerve
• Sural nerve, which is formed by the union of cutaneous branches from the tibial and common fibular nerves
• Lateral plantar nerve, which stems from the tibial nerve

Blood supply

Blood supply to the transverse tarsal joint is from the lateral tarsal artery, a branch of the dorsalis pedis artery. The latter originates from the anterior tibial artery.

Movements

In terms of movements, the surrounding ligamentous reinforcements of the transverse tarsal joint create two functional entities which operate concomitantly. One entity, formed by the talus and calcaneus, moves as a functional unit relative to the fixed navicular and cuboid bones. Movement of the transverse tarsal joint is always mechanically linked with that of the functional (talocalcaneal) subtalar joint. This is evident during weight loading of the subtalar joint, which is accompanied by a small degree of movement of the transverse tarsal joint.

The movement of the transverse tarsal joint is biaxial (around two axes) and triplanar (i.e. occurs in all three cardinal planes). The two axes around which the transverse tarsal joint moves are longitudinal and oblique. The longitudinal axis points superiorly, 15° to the transverse plane, and 9° medial to the sagittal plane. The oblique axis also points superiorly, 52° to the transverse plane and 57° medial to the sagittal plane.

The biaxial movements of the transverse tarsal joint have one degree of freedom, which involves supination and pronation. Both are triplanar, occurring in all three cardinal planes.

Supination is a complex movement involving three motions; inversion, adduction and plantarflexion. During supination, the naviculocuboid unit rotates relative to the bifurcate ligament. This involves a superior movement of the navicular bone at the talonavicular joint and an inferior movement of the cuboid at the calcaneocuboid joint. Pronation is an equally complex, but opposite movement. It involves a combination of three motions; eversion, abduction and dorsiflexion. During pronation, the reverse occurs; rotation of the naviculocuboid unit involves an inferior movement of the navicular bone at the talonavicular joint and a superior movement of the cuboid at the calcaneocuboid joint.

Although these cardinal movements (inversion/eversion, adduction/abduction and plantar/dorsiflexion) will be described individually below, it’s important to emphasize that they always occur synchronously with each other, and never in isolation due to the axes of rotation about which movement occurs. It should be also noted that the terms supination/pronation and inversion/eversion are regularly used interchangeably in the literature, despite the aforementioned kinesiologic difference in their definitions.

Inversion and eversion, if considered in isolation, take place around the orthogonal longitudinal axis of the foot. They are the dominant movements when rotation occurs around the longitudinal axis of the joint, due to the fact that this axis is more longitudinal than vertical. The range of motion (RoM) of inversion is approximately 8° to 10°, while the RoM of eversion ranges between 2° and 3°. These values represent between one half and one third of the RoM magnitude of the subtalar joint. During inversion, the sole of the foot rotates towards the midline, pointing the lateral border of the foot inferiorly. Eversion is the opposite. The sole of the foot is orientated laterally and the medial border is directed inferiorly.

Abduction (external rotation) and adduction (internal rotation) take place around a vertical axis in the transverse plane. They also take place at the transverse tarsal joint, but with a lesser RoM compared to inversion and eversion. During abduction, the naviculocuboid unit moves medially, temporarily increasing in the joint cavity of the talonavicular joint. However, the strength of the surrounding ligaments maintains the integrity of the joint, preventing excessing cavity enlargement and moving the forefoot anterolaterally. Adduction involves the opposite movements; here naviculocuboid unit moves laterally, temporarily decreasing the joint cavity of the talonavicular joint. The surrounding ligaments subsequently protect the joints and force the forefoot to move anteromedially.

Dorsiflexion and plantarflexion at the transverse tarsal joint is minor compared to the previous pairs of movements. They mostly occur around the oblique axis of the transverse tarsal joint, due to the fact that this axis is more mediolaterally oriented than longitudinal. Some studies have shown that up to 12% of the first 30 degrees of total foot plantarflexion can occur at the transverse tarsal joint.

By facilitating supination and pronation, the transverse tarsal joint has important functional implications. During weight bearing on uneven surfaces or when turning, the leg and hindfoot supinate and pronate on the forefoot. In turn, this results in a series of continuously adjusting movements that maintain balance.

The close packed position of the transverse tarsal joint is full supination, while open packed (resting) position is midway between the extremes of the total range of motion. The joint’s capsular pattern is dorsiflexion, followed by plantar flexion, adduction and medial rotation. Accessory movements of the transverse tarsal joint is possible at the calcaneocuboid joint. These include superoinferior sliding of the calcaneus relative to the cuboid.

Muscles acting on the transverse tarsal joint

No muscles have immediate actions on the transverse tarsal joint. Instead, movement of this joint relies primarily on the motion of the nearby subtalar (talocalcaneal) and (ankle) talocrural joints.

The prime muscles causing supination at the transverse tarsal joint are tibialis anterior and posterior. They occupy the anterior and posterior compartments of the leg, respectively, and extend medially, inserting onto the medial aspect of the foot. In addition, the two digit flexor muscles (flexor digitorum longus, flexor hallucis longus) contribute to this movement.

The antagonists of the foot inverters are muscles extending laterally, inserting into the lateral aspect of the foot. They are responsible for pronation. The prime pronatorsare fibularis longus and brevis, which occupy the lateral compartment of the leg. The remaining two contributors, fibularis tertius and extensor digitorum longus, are situated within the anterior compartment of the leg.