Leg and Foot Anatomy

• The leg and foot complex is essential for weight bearing, balance, and locomotion.
• It consists of the lower leg (tibia and fibula), ankle, hindfoot (talus and calcaneus), midfoot (navicular, cuboid, and cuneiforms), and forefoot (metatarsals and phalanges).
• Bones, joints, ligaments, muscles, nerves, and blood vessels all contribute to its function.

Bones of the Lower Leg

• Tibia: The larger, weight-bearing bone of the lower leg.
• Fibula: The smaller, non-weight-bearing bone located laterally.
• The proximal Tibiofibular joint is a synovial joint that allows slight gliding and rotation.
• The distal Tibiofibular joint is a syndesmosis joint connected by strong interosseous ligaments.

Ankle Joint (Talocrural Joint)

• Formed by the articulation of the distal tibia and fibula.
• A mortise is created by the tibia and fibula which surrounds the talus.
• Functions primarily in plantarflexion and dorsiflexion.
• Classified as a hinge (ginglymus) joint with one degree of freedom.

Subtalar Joint (Talocalcaneal Joint)

• Formed by the articulation between the talus and calcaneus.
• Allows for inversion and eversion.
• Important for adapting to uneven surfaces.

Midfoot Joints

• Consists of the navicular, cuboid, and three cuneiform bones.
• Chopart's joint (talonavicular and calcaneocuboid joints) contributes to foot inversion and eversion.
• Lisfranc joint (tarsometatarsal joints) provides stability to the midfoot.

Forefoot Joints

• Metatarsophalangeal (MTP) joints: condyloid joints that allow flexion, extension, abduction, and adduction.
• Interphalangeal (IP) joints: hinge joints that allow flexion and extension of the toes.

Arches of the Foot

• Medial Longitudinal Arch: Formed by the calcaneus, talus, navicular, cuneiforms, and the first three metatarsals.
• Lateral Longitudinal Arch: Formed by the calcaneus, cuboid, and fourth and fifth metatarsals.
• Transverse Arch: Formed by the cuneiforms, cuboid, and metatarsal bases.
• Arches provide shock absorption and distribute weight during weight-bearing activities.
• Plantar fascia supports the arches and contributes to the windlass mechanism.

Ligaments of the Ankle and Foot

• Deltoid Ligament: Located on the medial side of the ankle.
• Resist excessive eversion.
• Anterior Talofibular Ligament (ATFL): Located on the lateral side of the ankle.
• Calcaneofibular Ligament (CFL): Located on the lateral side of the ankle.
• Posterior Talofibular Ligament (PTFL): Located on the lateral side of the ankle.
• ATFL, CFL, and PTFL resist excessive inversion and plantarflexion

Muscles of the Lower Leg

• Anterior Compartment: Includes tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius.
• Responsible for dorsiflexion and toe extension
• Lateral Compartment: Includes fibularis longus and fibularis brevis.
• Responsible for eversion of the foot.
• Superficial Posterior Compartment: Includes gastrocnemius, soleus, and plantaris.
• Responsible for plantarflexion of the ankle.
• Deep Posterior Compartment: Includes tibialis posterior, flexor digitorum longus, and flexor hallucis longus.
• Responsible for plantarflexion, inversion, and toe flexion.

Ankle and Foot Kinematics

• Open Chain: The foot is not in contact with the ground, and the leg rotates.
• Closed Chain: The foot is fixed on the ground, and the leg moves over the foot.
• Pronation: A combination of dorsiflexion, eversion, and abduction.
• Supination: A combination of plantarflexion, inversion, and adduction.
• During the gait cycle, the foot pronates during the loading response to absorb shock and adapts to uneven surfaces.
• During push-off, the foot supinates to provide a rigid lever for propulsion.

Nerves of the Lower Leg and Foot

• Tibial Nerve: Innervates the muscles in the posterior compartment of the lower leg and the plantar muscles of the foot.
• Common Fibular (Peroneal) Nerve: Divides into the superficial and deep fibular nerves.
• Deep Fibular Nerve: Innervates the muscles in the anterior compartment of the lower leg.
• Superficial Fibular Nerve: Innervates the muscles in the lateral compartment of the lower leg.
• Sural Nerve: Sensory innervation to the lateral aspect of the foot and ankle.

Blood Supply

• Anterior tibial artery supplies the anterior compartment of the leg and becomes the dorsalis pedis artery in the foot.
• Posterior tibial artery supplies the posterior compartment of the leg and branches into the medial and lateral plantar arteries in the foot.
• Fibular (Peroneal) artery supplies the lateral compartment of the leg.

Functional Anatomy

• Weight Bearing: The foot and ankle must be able to support the body's weight during standing, walking, and running.
• Balance: The muscles of the lower leg and foot work together to maintain balance and prevent falls.
• Gait: The ankle and foot play a crucial role in the gait cycle, providing shock absorption, stability, and propulsion.
• Adaptability: The joints of the foot allow it to adapt to uneven surfaces and maintain contact with the ground.

Kinesiology of the Ankle and Foot

• Range of Motion: Ankle dorsiflexion is approximately 20 degrees, and plantarflexion is approximately 50 degrees.
• Subtalar joint inversion and eversion range from 20-30 degrees.
• Muscle Actions: The muscles of the lower leg work in synergy to control movement at the ankle and foot.
• During plantarflexion, the gastrocnemius and soleus are the primary movers.
• During dorsiflexion, the tibialis anterior is the primary mover.
• During eversion, the fibularis longus and brevis are the primary movers.
• During inversion, the tibialis posterior and anterior are the primary movers.

Common Injuries

• Ankle Sprains: Lateral ankle sprains are the most common, involving the ATFL, CFL, and PTFL.
• Plantar Fasciitis: Inflammation of the plantar fascia, causing heel pain.
• Achilles Tendinitis: Inflammation of the Achilles tendon, causing pain in the back of the heel.
• Stress Fractures: Common in the metatarsals, caused by repetitive stress and overuse.