# ANATOMY ANATOMY There are 26 (25 with variant) main bones in the foot (seven tarsal bones, five metatarsals and 14 phalanges [13 in the biphalangeal fifth toe variant]) plus the two sesamoids of the hallux and a variable number of other sesamoid and accessory bones. Movements at the ankle joint are mainly dorsiflexion and plantarflexion, but are more complex than this. The joint is actually a truncated section of a cone, meaning that the motion is not simply a hinge; in addition, movement of the ankle leads to rotation of the fib ula at the syndesmosis. This means that the foot externally rotates with dorsiflexion and internally rotates with plantarflexion. Stability is conferred upon the ankle by the congruence of the mortice and the integrity of principally the medial, lateral and inferior tibiofibular ligaments. The subtalar joint is divided into anterior, middle and posterior facets and, along with the talonavicular and calca neocuboid joints, makes up the triple joint complex. These joints are responsible f or inversion and eversion of the hind- and midfoot. The joints are co-dependent such that limitation of one a ff ects movement at the others. Fusion of the triple complex slightly a ff ects movement at the ankle and vice versa. The second tarsometatarsal (TMT) joint is recessed relative to the first and third and acts as a ‘keystone’. Disruption of this joint (Lisfranc’s injury) leads to loss of the transverse arch and an acquired flat foot. The lower leg is divided into f our compartments: /uni25CF the superficial posterior – gastrocnemius, soleus and plantaris; Jacques Lisfranc , 1790–1847, Professor of Surgery and Operative Medicine, Paris, France. /uni25CF the deep posterior – tibialis posterior, flexor digitorum longus and flexor hallucis longus (FHL); /uni25CF the lateral – peroneus brevis and peroneus longus; /uni25CF the anterior – tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius. There is only one muscle on the dorsum of the foot, the extensor digitorum brevis. The muscles on the plantar aspect of the foot are divided into four layers, the first being the most superficial, and the course of the neur ovascular structures is a favourite examination topic. The plantar fascia is a very important structure that takes its origin from the heel and inserts into the bases of the proximal phalanges of the toes. At toe-o ff , the fascia tightens and accentuates the medial plantar arch and helps provide a rigid lever arm, the so-called ‘windlass mechanism’. This is essential in the preservation of the integ - rity of the arch of the foot and function of the toes. The blood supply of the foot is from the anterior tibial, the posterior tibial and the peroneal arteries. The following nerves - supply sensation to the foot: posterior tibial, saphenous, sural, superficial and deep peroneal ( Figure 41.1 ). Summary box 41.1 Anatomy of the foot /uni25CF /uni25CF /uni25CF The principles behind the treatment of each condition, be • it conservative or surgical The signi /f_i cance of progressive neurological diseases • There are 26 major bones in the foot There are four layers of muscles in the sole of the foot The blood supply of the foot is from the anterior and posterior tibial arteries plus the peroneal artery or medial plantar nerve (from tibial nerve) Medial plantar nerve (branch of tibial nerve) Lateral plantar branch of medial plantar nerve (branch of tibial nerve) Sural nerve Saphenous nerve Super /f_i cial peroneal nerve Medial calcaneal nerve (tibial nerve) Lateral plantar nerve Figure 41.1 Cutaneous nerve supply of the foot (courtesy of Bartleby.com). ANATOMY There are 26 (25 with variant) main bones in the foot (seven tarsal bones, five metatarsals and 14 phalanges [13 in the biphalangeal fifth toe variant]) plus the two sesamoids of the hallux and a variable number of other sesamoid and accessory bones. Movements at the ankle joint are mainly dorsiflexion and plantarflexion, but are more complex than this. The joint is actually a truncated section of a cone, meaning that the motion is not simply a hinge; in addition, movement of the ankle leads to rotation of the fib ula at the syndesmosis. This means that the foot externally rotates with dorsiflexion and internally rotates with plantarflexion. Stability is conferred upon the ankle by the congruence of the mortice and the integrity of principally the medial, lateral and inferior tibiofibular ligaments. The subtalar joint is divided into anterior, middle and posterior facets and, along with the talonavicular and calca neocuboid joints, makes up the triple joint complex. These joints are responsible f or inversion and eversion of the hind- and midfoot. The joints are co-dependent such that limitation of one a ff ects movement at the others. Fusion of the triple complex slightly a ff ects movement at the ankle and vice versa. The second tarsometatarsal (TMT) joint is recessed relative to the first and third and acts as a ‘keystone’. Disruption of this joint (Lisfranc’s injury) leads to loss of the transverse arch and an acquired flat foot. The lower leg is divided into f our compartments: /uni25CF the superficial posterior – gastrocnemius, soleus and plantaris; Jacques Lisfranc , 1790–1847, Professor of Surgery and Operative Medicine, Paris, France. /uni25CF the deep posterior – tibialis posterior, flexor digitorum longus and flexor hallucis longus (FHL); /uni25CF the lateral – peroneus brevis and peroneus longus; /uni25CF the anterior – tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius. There is only one muscle on the dorsum of the foot, the extensor digitorum brevis. The muscles on the plantar aspect of the foot are divided into four layers, the first being the most superficial, and the course of the neur ovascular structures is a favourite examination topic. The plantar fascia is a very important structure that takes its origin from the heel and inserts into the bases of the proximal phalanges of the toes. At toe-o ff , the fascia tightens and accentuates the medial plantar arch and helps provide a rigid lever arm, the so-called ‘windlass mechanism’. This is essential in the preservation of the integ - rity of the arch of the foot and function of the toes. The blood supply of the foot is from the anterior tibial, the posterior tibial and the peroneal arteries. The following nerves - supply sensation to the foot: posterior tibial, saphenous, sural, superficial and deep peroneal ( Figure 41.1 ). Summary box 41.1 Anatomy of the foot /uni25CF /uni25CF /uni25CF The principles behind the treatment of each condition, be • it conservative or surgical The signi /f_i cance of progressive neurological diseases • There are 26 major bones in the foot There are four layers of muscles in the sole of the foot The blood supply of the foot is from the anterior and posterior tibial arteries plus the peroneal artery or medial plantar nerve (from tibial nerve) Medial plantar nerve (branch of tibial nerve) Lateral plantar branch of medial plantar nerve (branch of tibial nerve) Sural nerve Saphenous nerve Super /f_i cial peroneal nerve Medial calcaneal nerve (tibial nerve) Lateral plantar nerve Figure 41.1 Cutaneous nerve supply of the foot (courtesy of Bartleby.com). ANATOMY There are 26 (25 with variant) main bones in the foot (seven tarsal bones, five metatarsals and 14 phalanges [13 in the biphalangeal fifth toe variant]) plus the two sesamoids of the hallux and a variable number of other sesamoid and accessory bones. Movements at the ankle joint are mainly dorsiflexion and plantarflexion, but are more complex than this. The joint is actually a truncated section of a cone, meaning that the motion is not simply a hinge; in addition, movement of the ankle leads to rotation of the fib ula at the syndesmosis. This means that the foot externally rotates with dorsiflexion and internally rotates with plantarflexion. Stability is conferred upon the ankle by the congruence of the mortice and the integrity of principally the medial, lateral and inferior tibiofibular ligaments. The subtalar joint is divided into anterior, middle and posterior facets and, along with the talonavicular and calca neocuboid joints, makes up the triple joint complex. These joints are responsible f or inversion and eversion of the hind- and midfoot. The joints are co-dependent such that limitation of one a ff ects movement at the others. Fusion of the triple complex slightly a ff ects movement at the ankle and vice versa. The second tarsometatarsal (TMT) joint is recessed relative to the first and third and acts as a ‘keystone’. Disruption of this joint (Lisfranc’s injury) leads to loss of the transverse arch and an acquired flat foot. The lower leg is divided into f our compartments: /uni25CF the superficial posterior – gastrocnemius, soleus and plantaris; Jacques Lisfranc , 1790–1847, Professor of Surgery and Operative Medicine, Paris, France. /uni25CF the deep posterior – tibialis posterior, flexor digitorum longus and flexor hallucis longus (FHL); /uni25CF the lateral – peroneus brevis and peroneus longus; /uni25CF the anterior – tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius. There is only one muscle on the dorsum of the foot, the extensor digitorum brevis. The muscles on the plantar aspect of the foot are divided into four layers, the first being the most superficial, and the course of the neur ovascular structures is a favourite examination topic. The plantar fascia is a very important structure that takes its origin from the heel and inserts into the bases of the proximal phalanges of the toes. At toe-o ff , the fascia tightens and accentuates the medial plantar arch and helps provide a rigid lever arm, the so-called ‘windlass mechanism’. This is essential in the preservation of the integ - rity of the arch of the foot and function of the toes. The blood supply of the foot is from the anterior tibial, the posterior tibial and the peroneal arteries. The following nerves - supply sensation to the foot: posterior tibial, saphenous, sural, superficial and deep peroneal ( Figure 41.1 ). Summary box 41.1 Anatomy of the foot /uni25CF /uni25CF /uni25CF The principles behind the treatment of each condition, be • it conservative or surgical The signi /f_i cance of progressive neurological diseases • There are 26 major bones in the foot There are four layers of muscles in the sole of the foot The blood supply of the foot is from the anterior and posterior tibial arteries plus the peroneal artery or medial plantar nerve (from tibial nerve) Medial plantar nerve (branch of tibial nerve) Lateral plantar branch of medial plantar nerve (branch of tibial nerve) Sural nerve Saphenous nerve Super /f_i cial peroneal nerve Medial calcaneal nerve (tibial nerve) Lateral plantar nerve Figure 41.1 Cutaneous nerve supply of the foot (courtesy of Bartleby.com).