Tarsals (7 bones)

1. Overview

The tarsals are a group of seven irregularly shaped bones that make up the posterior portion of the foot, forming the ankle and proximal foot region. These bones are integral to weight bearing, stability, and foot mobility. They form the bony framework of the hindfoot and midfoot and articulate with the tibia and fibula superiorly and the metatarsals distally.

2. Location

The tarsal bones are located in the posterior part of the foot, divided into two regions:

• Hindfoot: Includes the talus and calcaneus bones.

• Midfoot: Comprises the navicular, cuboid, and three cuneiform bones (medial, intermediate, and lateral).

These bones lie between the bones of the leg (tibia and fibula) and the five metatarsal bones of the forefoot.

3. Structure

The seven tarsal bones are:

• Talus: Forms the lower part of the ankle joint, articulates with the tibia and fibula.

• Calcaneus: The largest tarsal bone; forms the heel and supports the talus.

• Navicular: Medial midfoot bone that articulates with the talus and cuneiforms.

• Cuboid: Lateral midfoot bone that articulates with the calcaneus and lateral metatarsals.

• Three cuneiforms:

  • Medial, intermediate, and lateral.

  • Located between the navicular and the bases of the first three metatarsals.

Each tarsal bone is covered with articular cartilage at synovial joint surfaces and has roughened areas for ligament and tendon attachment.

4. Function

Tarsal bones perform multiple critical mechanical and supportive functions:

• Bear body weight: Transfer loads from the leg to the foot during standing and movement.

• Form joints: Contribute to complex articulations like the subtalar, transverse tarsal, and tarsometatarsal joints.

• Provide foot structure: Maintain the arches of the foot (especially the medial longitudinal arch).

• Enable movement: Allow inversion, eversion, dorsiflexion, and plantarflexion of the foot.

5. Physiological role(s)

In addition to mechanical functions, the tarsals contribute to dynamic motion and sensory feedback:

• Shock absorption: Their articulation and slight mobility help dissipate impact forces during walking and running.

• Proprioception: Ligaments and joint capsules surrounding tarsals contain mechanoreceptors that aid balance and gait control.

• Stabilize gait: Work with surrounding muscles and tendons (e.g., tibialis posterior, peroneals) to stabilize the foot through the gait cycle.

6. Clinical Significance

The tarsal bones are involved in various orthopedic and podiatric conditions:

• Fractures:

  • Calcaneal fracture: Often due to high-energy trauma like falls from height.

  • Talus fracture: Can disrupt blood supply and lead to avascular necrosis.

  • Navicular stress fracture: Common in athletes due to repetitive loading.

• Tarsal coalition:

  • Congenital fusion of two or more tarsal bones (e.g., talocalcaneal coalition), which can limit foot mobility and cause pain.

• Flatfoot (pes planus):

  • Collapse of the medial arch often involves dysfunction of tarsal alignment, especially the talonavicular joint.

• Tarsal tunnel syndrome:

  • Compression of the tibial nerve as it passes near the tarsal bones, leading to pain and numbness in the sole.

• Arthritis:

  • Osteoarthritis or post-traumatic arthritis can affect tarsal joints, particularly after injury.