ABC's of Lower Extremity Anatomy

Lower Extremity Anatomy is an extremely important course for podiatry students as it lays out the groundwork for our field. Here are a few important structures and diagnostic tests seen in lectures and labs. This is not an all-inclusive review.

Achilles Tendon

  • Tendon of gastrocnemius and soleus attaches to the posterior surface of the calcaneus.

Baxter’s Nerve

• Nerve on plantar surface of the foot. Motor innervation includes flexor digitorum brevis, quadratus plantae, and abductor digiti minimi. Sensory Innervation: calcaneal periosteum and long plantar ligament.

Crural Fascia

  • The deep fascia covering the compartments of the leg.

Dorsalis Pedis

• Branch of the anterior tibial artery. Can give rise to cutaneous branches that supply skin on the dorsum of the foot. Clinical Point: dorsalis pedis pulse is checked when assessing blood flow to the fleet.

Extensor Expansion

• Triangular membranous sheath that surrounds the dorsum and sides of an MTPJ and extends beyond DIPJ.

Flexor Retinaculum

 • Holds the tendon of tibialis posterior, tendon of flexor digitorum longus, posterior tibial vasculature, tibial nerve, and flexor hallucis longus

Great Saphenous Vein

• This vein runs on the medial side of the lower extremity and terminates past the medial malleolus in the medial marginal vein contributing to the dorsal venous network.

Hallucal Sesamoids

• Constant, small, rounded bones, associated with the tendon of flexor hallucis brevis. Functions can include altering the pull of a tendon, providing mechanical advantage and protecting tendon from friction.

Intrinsic Muscles of the Foot

• Medial Compartment: abductor hallucis and flexor hallucis brevis

• Central Compartment: flexor digitorum brevis, quadratus plantae, lumbricals, adductor hallucis, and interossei

• Lateral Compartment: abductor digiti minimi and Flexor digiti minimi

Joints Proximal Interphalangeal

• Joint (PIPJ), Interphalangeal Joint (IPJ), Distal Phalangeal Joint (DIPJ), Metatarsophalangeal Joint (MTPJ). Can be insertion sites for Flexor Digitorum Brexis and aid in plantarflexion and dorsiflexion of the toes.
  

Kager’s Triangle

• Fat-filled space separating the Achilles tendon from the deep transverse intermuscular septum.

Lumbricals

 • Have an attachment to the flexor digitorum longus tendon and are all innervated by lateral plantar nerve EXCEPT the first lumbrical. The lumbricals simultaneously plantarflex the MTPJ and dorsiflex the IPJs of the lateral digits Metatarsals • Miniature long bones numbered 1-5 beginning with medial ray (hallux). The head articulates distally while the base articulates proximally.

Neuroma (Morton’s)

• Not a true tumor but a perineural fibrosis. Can have radiating forefoot pain also numbness between affected digits.

Oblique Popliteal Ligament

• Inside the knee joint capsule and associated with the middle genicular artery.

Posterior Tibial Artery

  • Branches include circumflex fibular, fibular, nutrient artery to tibia, muscular, communicating, posterior medial malleolar, medial and lateral plantar, and medial calcaneal.

Quadratus Plantae

• Muscle in medial compartment of the plantar foot, innervation and blood supply come from lateral plantar neurovasculature. Major action is to assist flexor digitorum longus in Plantarflexion of the lateral MTPJ and IPJ.

Recurrent Branch of Posterior Tibial

 • When present this artery is the first branch from the anterior tibial artery, followed by circumflex fibular and recurrent branch of tibial artery.

Spring Ligament

 • Also known as the plantar calcaneonavicular ligament. This ligament brings support to the medial longitudinal arch of the foot. Dysfunction in this ligament can cause a flat foot deformity.

Tibial Nerve

• Innervates posterior muscular compartment of leg including flexor hallucis longus, flexor digitorum longus, tibialis posterior, popliteus, plantaris, gastrocnemius, and soleus.

Ultrasounds

 • Diagnostic imaging can help determine if there is a deep vein thrombosis of the lower extremity.

Venous Comitantes

  • Two or more deep veins that travel with an artery. The relationship between the accompanying vein and artery allows for an arteriovenous pump and a countercurrent heat exchange.

Wing/Hood

• Two triangular sheets, one on each side of the toe, which meet at their dorsal edges

X-rays

• Diagnostic imaging that can be used to visualize the bones of the lower extremity.

Y-shaped Inferior extensor retinaculum

• Holds tendons of four muscles: fibularis tertius, extensor digitorum longus, tibialis anterior, and extensor hallucis longus.

Zeugopod

• Limb segment including the tibia and fibula.