Tarsal Bones and Foot Joints

Tarsal Bones and Foot Structure

• 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.

Foot Movements and Tarsal Joints

• 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

Subtalar Joint

• 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.

Talocalcaneonavicular Joint

• 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.

Midtarsal Joint Complex

• Located between the midtarsal bones.
• It is a complex because it contains multiple joints.
• Includes parts of the talocalcaneonavicular joint and the calcaneocuboid joint.

Interconnection of Joints

• 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.

Ligaments Supporting the Tarsal Joints

• 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.

Plantar Ligaments

• 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.

Plantar Aponeurosis

• 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.

Joint Cavities Review

• 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.

Foot Movement Axes

• 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.

Simplified Uniplanar Movements

• 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.

Oblique Axis and Triplanar Movements

• 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.

Muscle Positioning for Foot Movements

• 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.