Type
- Synovial joint, ball-and-socket variety.
- Important for inversion and eversion of the foot.
Articular Surfaces
It is a complex joint involving talus, calcaneus, and navicular bones:
- Head of talus = “ball” of the joint.
- Socket formed by:
- Posterior surface of navicular bone.
- Spring ligament (plantar calcaneonavicular ligament).
- Anterior surface of sustentaculum tali (calcaneus).
- Upper surface of calcaneus (anterior facet).
Capsule & Synovial Membrane
- Capsule: thin, surrounds joint, attached around articular margins.
- Synovial cavity is continuous with that of the subtalar joint in most cases.
Ligaments
- 1. Plantar calcaneonavicular ligament (spring ligament):
- Runs from sustentaculum tali (calcaneus) → plantar surface of navicular.
- Supports head of talus from below.
- Maintains medial longitudinal arch of foot.
2. Dorsal talonavicular ligament:
- Weak, from dorsal surface of talus → navicular.
3. Bifurcate ligament (calcaneonavicular part):
- Y-shaped, attaches calcaneus → navicular & cuboid.
4. Deltoid ligament (tibionavicular part):
- From medial malleolus → navicular (supports medially).
Movements
- Part of transverse tarsal joint (with calcaneocuboid joint).
- Movements:
- Inversion (sole turns medially).
- Eversion (sole turns laterally).
- Small gliding movements.