chapter 19

Overview of the Leg, Ankle, and Foot Anatomy

Main Functions of Leg, Ankle, and Foot

  • Transmission of Forces:

    • Transfers forces from the body to supporting surfaces.

    • Transfers forces from supporting surfaces back to the body.

  • Base of Support: Acts as a base for maintaining stability when standing or moving.

  • Accommodation for Various Surfaces: Enables movement and adjustment based on different ground conditions.

Anatomy of the Leg

  • Major Bones: Tibia and Fibula.

    • Proximal Joint: Tibiofibular joint (proximal).

    • Distal Joint: Tibiofibular joint (distal).

    • Connective structures: Interosseous membrane connects both bones.

Ankle Joint Anatomy

  • Main Components: Talus, Tibia, and Fibula.

    • The talus allows the tibia to rest atop and interacts with the fibula on the lateral side.

    • Mortise Joint: Refers to the structure formed by the lower ends of the tibia and fibula shaping around the talus.

  • Joint Functionality:

    • Movement is primarily limited to dorsiflexion and plantar flexion.

    • Limited lateral movement is supported by the fibula.

Foot Anatomy

  • Divisions:

    • Hindfoot: Talus and calcaneus.

    • Midfoot: Navicular, cuboid, three cuneiforms.

    • Forefoot: Metatarsals and phalanges.

  • Normal Foot Alignment: Plantigrade position (90° angle between foot and leg).

Bones in the Foot

  • Hindfoot:

    • Talus: Positioned above calcaneus and underneath tibia.

    • Calcaneus: The heel bone.

  • Midfoot:

    • Navicular: Medially located, characterized by tuberosity felt when palpated.

    • Cuboid: Located laterally between calcaneus and fourth/fifth metatarsals.

    • Cuneiforms: Three bones - labeled as first (medial), second, and third.

Structure: Midfoot comprises tarsals that support weight during movement.

  • Forefoot Structure:

    • Metatarsals: Bones of the mid-foot leading to toes.

    • Phalanges: Bones of the toes; big toe has one joint (IP), others have PIP and DIP.

Joint Movements in the Ankle

  • Dorsiflexion:

    • Angle increases, toes move upward:

    • Range: 0° to 20° (sagittal plane, frontal axis).

  • Plantar Flexion:

    • Angle decreases, toes point downward:

    • Range: 0° to 50°.

  • Inversion and Eversion: Foot movements that occur in frontal plane about sagittal axis.

    • Inversion: Foot turns inward - range of motion: 0° to 35°.

    • Eversion: Foot turns outward - range of motion: 0° to 15°.

  • Supination and Pronation:

    • Supination: Combination of inversion, adduction, and plantar flexion.

    • Pronation: Combination of eversion, abduction, and dorsiflexion.

Ligaments of the Foot

  • Deltoid Ligament: Four parts, strong, medial, supports the medial longitudinal arch.

    • Tibionavicular (anterior), Tibiocalcaneal (middle), Posterior tibiotalar (posterior), and Anterior tibiotalar (deep).

  • Lateral Ligaments: Weaker, prone to sprains due to mechanics, includes anterior talofibular, posterior talofibular, calcaneofibular.

Muscles of the Foot

Extrinsic Muscles

  • Superficial Posterior:

    • Gastrocnemius: Originates from femur, performs plantar flexion and knee flexion.

    • Soleus: Deep to gastrocnemius, only involved in plantar flexion.

    • Plantaris: Minimal contribution to knee flexion, more important in plantar flexion.

  • Deep Posterior:

    • Tibialis Posterior: Inversion and plantar flexion, primarily acts on the medial part of the foot.

    • Flexor Digitorum Longus: Flexes distal phalanges two through five; helps with plantar flexion.

    • Flexor Hallucis Longus: Flexes the great toe, aids in plantar flexion and inversion.

  • Anterior:

    • Tibialis Anterior: Main dorsiflexor, aids in inversion.

    • Extensor Hallucis Longus: Dorsiflexion of foot and extension of big toe.

    • Extensor Digitorum Longus: Extends lesser toes and assists in dorsiflexion.

  • Lateral:

    • Fibularis Longus: Plantar flexion and eversion.

    • Fibularis Brevis: Aids in plantar flexion and eversion.

    • Fibularis Tertius: Less common, assists with dorsiflexion and eversion.

Intrinsic Muscles

  • Four Layers:

    • 1st Layer: Flexor digitorum brevis, abductor hallucis, abductor digiti minimi.

    • 2nd Layer: Quadratus plantae and lumbricals.

    • 3rd Layer: Flexor hallucis brevis and adductor hallucis, flexor digiti minimi.

    • 4th Layer: Interossei (dorsal and plantar).

Key Clinical Applications

  • Pathologies:

    • Shin Splints: Inflammation due to overuse.

    • Ankle Sprains: Most commonly inversion sprains affecting the lateral ligaments.

    • Achilles Tendinitis: Inflammation of Achilles tendon.

    • Fractures: Often at malleoli due to inversion stresses.

    • Morton's Neuroma: Nerve compression between toes, often requiring wider toe boxes in shoes to alleviate pain.