Tarsal Bones and Foot Joints

Tarsal bones are located in the tarsus of the foot, which includes the hindfoot and midfoot.
Hindfoot: Talus and Calcaneus
Midfoot: Navicular, three Cuneiforms, and Cuboid bone
These short bones are important for:
- Weight distribution.
- Providing balance and stability through subtle movements and adaptations.
- Ensuring congruent contact with the ground.
They contribute to the structural composition of foot arches:
- Medial and Lateral Longitudinal Arches
- Important for springing off the foot during walking.

Movements like eversion and inversion are enabled by the tarsal joints.
The ankle joint (talocrural joint) between the tibia, fibula, and talus is a hinge joint, allowing only flexion (plantar flexion) and extension (dorsiflexion).
All other foot movements occur within the tarsal joints themselves (subtalar).
Key joints enabling foot movements:
- Subtalar Joint
- Talocalcaneonavicular Joint
- Midtarsal Joint Complex

Located below the talus bone where the talus sits on top of the calcaneus.
The talus articulates with the posterior articular facet of the calcaneus (posterior talocalcaneal joint).
Also includes part of the talocalcaneonavicular joint.
The talus articulates with the medial and anterior calcaneal facets.
The calcaneus has three facets: posterior, middle, and anterior.

Located between the talus, calcaneus, and navicular bones.
The talus articulates with the middle articular facet on the calcaneus.
The joint is supported by the spring ligament (plantar calcaneonavicular ligament) which provides a border on the plantar surface.

All joints are highly connected and congruent.
They work together as a complete structure rather than having individual movements.
Movements like inversion and eversion occur between the subtalar joint and the talocalcaneonavicular joint, resting between the calcaneocuboidal joint.

Familiar ligaments cross over the bones covered and support the joints.
On the medial aspect, the deltoid ligament comprises four semi-connected ligaments between the tibia and tarsal bones.
- Tibial calcaneal and tibio navicular ligaments cross over the talus and insert into the tarsal bones.
- These ligaments support the medial aspect between the navicular and talus bones, preventing separation.
On the lateral side, the calcaneofibular ligament crosses over the talus and inserts at the calcaneus, starting at the fibula.
- This prevents hyper-inversion on the lateral aspect.

Long and short plantar ligaments support the plantar surface of the foot.
The long plantar ligament is superficial, running from the calcaneus to the tarsal bones and the bases of the metatarsals, supporting multiple joints.
The short plantar ligament runs from the calcaneus to the cuboid, supporting the midtarsal joint between the calcaneus and cuboid.
The plantar calcaneonavicular ligament (spring ligament) forms the floor of the talocalcaneonavicular joint, acting as a spring-like structure to aid in gait.

Can be felt on the medial plantar surface of the foot, stretching when the toes are extended.
Important for maintaining the arch of the foot during walking.

Three individual joints are separated by their own unique joint capsule, each with its own joint cavity.
Posterior talocalcaneal joint:
- Part of the subtalar joint.
Talocalcaneonavicular joint: Part of joint complex
- Has multiple individual joint cavities.
- Includes the middle and anterior articular facets for the talus on the calcaneus.
- Includes the articular facet on the navicular bone.
Calcaneocuboid joint cavity:
- Part of the midtarsal joint complex.
- Also includes the joint cavity between the navicular and the talus bone.

The talocrural joint has a mediolateral axis, enabling flexion and extension.
There are also vertical and anteroposterior axes.
Movements around a vertical axis differ in the foot because the foot extends 90 degrees from the body.

Flexion and extension occur around the mediolateral axis on the sagittal plane.
Abduction (toe away from the midline) and adduction (toe towards the midline) occur around the vertical axis.
Inversion (big toe up and inwards) and eversion (little toe up and outwards) occur around the anteroposterior axis.

The foot's lateral torsion leads to an oblique axis rather than standard anatomical axes.
The oblique axis runs from the anterior superior medial side to the posterior lateral aspect of the foot.
This creates triplanar movements, which combine three planes of movement.
Supination: adduction, plantar flexion, and inversion.
Pronation: abduction, dorsiflexion, and eversion.

Dorsiflexion: Muscles on the anterior side of the mediolateral axis pull the foot upwards.
Plantar flexion: Muscles on the posterior side of the mediolateral axis pull up on the calcaneus.
Inversion: Muscles to be positioned to bring the side of the foot inwards and upwards.
Eversion: Muscles to be positioned to bring the side of the foot outwards and upwards.
Adduction: Muscles to be positioned to bring the side of the foot towards the midline.
Abduction: Muscles to be positioned to bring the side of the foot away from the midline.
Supination: Combination action of muscles producing adduction, plantar flexion, and inversion.
Pronation: Combination action of muscles producing abduction, dorsiflexion, and eversion.