Anatomy of the Leg and Foot Muscles

Leg Anatomy

• The leg extends from the knee to the ankle.
• The leg's bony structure consists of the tibia (medially) and fibula (laterally). These run parallel.

Leg Compartments

• The leg is divided into three compartments: anterior (extensor), posterior (flexor), and lateral (fibular).
• These compartments are separated by interosseous membrane and intermuscular septa.
• The deep fascia attaches to the tibia's anterior and medial borders.

Anterior Compartment

• Muscles: Ankle dorsiflexors (extensors).
• Blood Vessels: Anterior tibial vessels.
• Nerves: Deep fibular nerve.
• Specific muscles include Tibialis Anterior, Extensor Hallucis Longus, Extensor Digitorum Longus, and Fibularis Tertius.

Muscles

• Four muscles dorsiflex the foot, extend the toes, and invert the foot; all are innervated by the deep fibular nerve.
• The muscles are Tibialis anterior, Extensor hallucis longus, Extensor digitorum longus, and Fibularis tertius.
• Details about origin, insertion, nerve supply, and action are provided in the tables for tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius.

Anterior Tibial Artery

• Originates in the posterior compartment of the leg.
• Travels through the interosseous membrane into the anterior compartment.
• Lies between the tibialis anterior and extensor hallucis longus tendons.
• Emerges from the leg, passing anterior to the ankle joint, and continues as the dorsalis pedis artery in the foot.
• Branches include recurrent branches around the knee joint, muscular branches, anterior medial malleolar artery, anterior lateral malleolar artery and dorsalis pedis artery.

Deep Fibular Nerve

• Originates in the lateral compartment, branching from the common fibular nerve.
• Passes deep to the extensor digitorum longus.
• Reaches the anterior interosseous membrane and descends with the anterior tibial artery.
• Innervates all muscles in the anterior compartment.
• Enters the dorsal aspect of the foot, innervating the extensor digitorum brevis.
• Contributes to the innervation of the first two dorsal interossei muscles.
• Supplies skin between the great and second toes.

Lateral Compartment

• Muscles: Two evertors of the ankle joint (Fibularis longus and Fibularis brevis).
• Blood Vessels: Perforating branches of the fibular artery.
• Nerves: Superficial fibular nerve.

Superficial Fibular Nerve

• Originates from the common fibular nerve.
• Supplies the fibularis muscles.
• Penetrates the deep fascia in the lower leg and enters the foot.
• Divides into medial and lateral branches.
• Supplies most dorsal areas of the foot and all toes, except: the web space between the great and second toes (supplied by deep fibular nerve) and the lateral side of the little toe (supplied by the sural branch of tibial nerve).

Ankle Retinacula

• Thickening of deep fascia on the lower leg.
• Five retinacula: two extensor retinacula (upper and lower), two fibular retinacula (upper and lower), and one flexor retinaculum.
• Maintain structures passing from the leg into the foot, preventing displacement.

Extensor Retinacula

• Superior extensor retinaculum: thickens distal leg deep fascia, superior to the ankle joint, attaches to anterior borders of fibula and tibia.
• Inferior extensor retinaculum: Y-shaped, attaches to lateral calcaneus, crosses foot medially to medial malleolus, and wraps around the foot medially to plantar aponeurosis.

Structures Deep to Extensor Retinacula

• From lateral to medial: tendon of fibularis tertius, tendon of extensor digitorum longus, dorsalis pedis artery, tendon of extensor hallucis longus, tendon of tibialis anterior.

Fibular Retinacula

• Superior fibular retinaculum: extends between the lateral malleolus and the calcaneus.
• Inferior fibular retinaculum: attaches to lateral surface calcaneus, blends with inferior extensor retinaculum.
• Fibular trochlea has septa separating compartments for fibularis brevis and longus.

Test your knowledge on the anatomy of the leg and foot, focusing on muscles, nerves, and arteries. This quiz covers key structures such as the fibularis muscles, retinacula, and the anterior tibial artery. Perfect for students of anatomy and healthcare professionals.