There are 29 muscles associated with the human foot. (10 foot/ankle and 19 intrinsic) Ten of these muscles originate outside of the foot itself but cross the ankle joint to act on the ankle joint and help position the foot. The other 19 muscles are referred to as intrinsic muscles of the foot and act only within the foot. The muscles covered in this article serve various roles in gait as well as posture. These muscles are also aided by the plantar fascia, managing the mechanical vectors of the foot. The muscles of the foot influence the posture and the shape of the foot, as well as providing the ability to transmit muscle tension not only towards the ground but also towards the whole body system.
During gestation, the presence of the limbs appears at the 4th post-ovulatory week in the embryos (3-6 mm long - stage 13). Each limb develops in a proximal-distal direction and the foot appears at about 4.5 weeks (stage 15). The cartilaginous skeleton and the muscles become visible in a few days and soon after the fingers can be observed (stage 18-19). The skeletal elements are first seen as mesodermal condensations which then condense in a definite order; ossification, in the form of a periosteal collar in the tubular bones, occurs subsequently. Vascular invasion of the tarsal bones occurs during the fetal period, while endochondral ossification does not begin in some tarsal bones until after birth.
The limbs develop from proliferation of the mesoderm of the somatopleural in the lateral region of the body, which forms outgrowths in correspondence of the lumbar tract (3rd-5th lumbar somite) for the hind limbs.
The blood supply to the foot begins primarily with the popliteal artery. The popliteal artery branches off the large superficial femoral artery and gives rise to the three main branches supplying the lower leg and foot. The three branches from proximal to distal are the anterior tibial artery, peroneal artery, and posterior tibial artery. The anterior tibial artery continues distally to supply the anterior and dorsal portions of the foot. Once the anterior tibial artery passes under the extensor retinaculum, it becomes the dorsalis pedis. This artery is commonly palpated for a pedal pulse. The dorsalis pedis continues under the extensor hallucis longus and passes between it and the extensor digitorum longus. The dorsalis pedis has three lateral branches named the proximal and distal tarsal arteries and the arcuate artery, and two medial branches named the medial tarsal arteries. The arcuate artery branches at the level of the 1st tarsal-metatarsal joint and courses over the metatarsals 2 to 4 to give rise to the dorsal metatarsal arteries 2 to 4. The first dorsal metatarsal artery branches directly off the dorsalis pedis. The metatarsal branches supply the dorsal interosseous muscles of the foot. The peroneal artery supplies the muscles of the lateral leg and the posterior foot. Finally, the posterior tibial artery supplies the posterior and lateral leg as well as the plantar surface of the foot.
The venous system of the lower limbs is composed of deep veins (which run between the muscles) and superficial veins (which constitute a complex network just below the skin). The two systems are joined by transfascial valved communications that constitute a real system, that of the perforating veins. The perforating veins have the function of favouring the outflow of the blood that flows in the system superficial (about 10%) towards the deep system.
In the sole of the foot, there is a sort of sponge, consisting of a complicated intertwining of superficial and deep veins which, at each step, is emptied by compression on the ground. Thanks to this mechanism, the blood is pushed over the ankle up to the calf.
The venous system originates in the microcirculation from the arterial capillaries (afferent branch) to continue with the venous capillaries that converge in the collecting venules first and then in the collecting veins, thus constituting the initial efferent branch of venous macrocirculation.
In the anterior region the dorsal venous network of the foot through the intercapitular veins that pass through the interdigital spaces; the digital veins, joining two to two in the interdigital spaces, originate the metatarsal veins that are directed in the deep plantar venous arch, converging in the lateral plantar veins; these, after joining posteriorly with the medial plantar veins, originate the two posterior tibial veins. The anterior tibialis originate from the deep veins of the dorsal region of the foot. The medial marginal vein of the foot ascending anterior to the medial malleolus forms the internal saphenous vein or the great saphenous vein. The lateral marginal vein of the foot ascending anterior to the lateral malleolus forms the small saphenous vein.
The lymph drained from the lower limb reaches the external and common iliac lymph node chains. The fingers and the sole of the foot are rich in superficial lymphatic vessels, which gather in the medial and lateral collectors. The lymph drained deeply from the foot, concerns above all the articular area, bone and muscle and aponeurosis; the lymph gathers in the popliteal and femoral collectors.
There will be discussion regarding innervation of the various muscles in greater detail in the sections that follow. The initial nerve that gives rise to most of the innervation of the lower extremity is the sciatic nerve. The sciatic nerve makes its way out of the lumbosacral plexus and passes under the piriformis muscle before traveling distally. Around the distal third of the femur, the sciatic nerve branches to give rise to the common fibular nerve and the tibial nerve. The tibial nerve continues distally to give rise to the medial calcaneal branches, the medial sural cutaneous nerve, and the medial and lateral plantar nerves. The common peroneal nerve gives rise to two main branches, the superficial peroneal and the deep peroneal nerves. The superficial peroneal nerve primarily gives rise to cutaneous branches that receive sensory information from the skin. The deep peroneal nerve supplies motor function to many of the muscles responsible for dorsiflexion of the foot.
Foot and Ankle
Extensor Digitorum Longus
Flexor Digitorum Longus
Flexor Hallucis Longus
Extensor Digitorum Brevis
Extensor Hallucis Brevis
Flexor Digitorum Brevis
Abductor Digiti Minimi
Flexor Hallucis Brevis
Oblique and Transverse Head of Adductor Hallucis
Flexor Digiti Minimi Brevis
Compartments of the Foot
The muscles of the foot are divided up into nine compartments encompassed by fascia. The medial compartment contains the abductor hallucis, flexor hallicus brevis, and the flexor hallucis longus tendon. The lateral compartment contains the abductor digiti minimi and the flexor digiti minimi. The superficial central compartment contains the flexor digitorum brevis, the four lumbricals, and the flexor digitorum longus tendons. The deep central (aka calcaneal) compartment contains the quadratus plantae and the posterior tibial neurovascular bundle. The deep central compartment also communicates with the deep posterior compartment of the lower leg. The adductor compartment contains the adductor hallucis muscle. There are four interosseous compartments; the first is between the first and second metatarsals and includes the first dorsal interosseous muscle, the second is between the second and third metatarsal and includes both the dorsal and plantar interosseous muscles. The two compartments between the third and fourth as well as the fourth and fifth metatarsals also include the dorsal and plantar interosseous muscles.
Recent studies have shown variability in the insertion of the tibialis anterior tendon insertion, which may be significant because different points of insertion may have different distributions of force distribution on the foot and ankle. These differences become important during anterior tibialis tendon ruptures when it may be important for biomechanics to match up the previous tendon type.
Accessory peroneal muscles
Peroneus quartus is an accessory muscle found to be present in anywhere from 6 to 22% of people depending on the study you read. It typically arises from the peroneus brevis muscle but has been found to originate from the peroneus tertius and longus muscles as well. This muscle has been found to have different insertions including the cuboid, the lateral tubercle of the calcaneus, the apophysis of the cochlea of the calcaneus or the retrotrochlear eminence of the calcaneus. In some instances this muscle belly will give rise to a tendon that inserts on a phalanx of the fifth digit, thus earning the name peroneus digiti quinti. The peroneus digiti quinti may, in this case, help to extend the fifth digit.
Several studies have shown the association of the presence of a peroneus quartus muscle and the presence of associated pathology. Several studies have shown symptomatology in the form of ankle pain even without any signs of trauma to the lateral ankle. Other pathology noted includes peroneal subluxation, tendinous calcification, and hypertrophy of the retrotrochlear eminence of the calcaneus causing pain.
The muscles that act directly on or around the foot are responsible for many of the actions that allow for normal gait as well as maintaining posture. Injuries to these muscles can result in many conditions that may interfere with the ability to complete activities of daily living. Achilles tendon rupture, hammer toe, and pes planus (flat foot) are some of the more common conditions associated with the muscles of the foot. Each of these affects patients in different ways and may come with other comorbidities as well. Treatment of these conditions varies based on severity and even the age of the patient. Conservative non-operative management Achilles tendon rupture, for example, has shown to be non-inferior to operative management in cases of older patients.
There is a direct relationship between the weakness of the foot muscles and the onset of pain when the foot is supported. Probably, the motivation is that the strength of the foot is not able to adequately manage the centre of mass, shifting the load to even weaker areas of the foot. Normally the centre of mass is managed by several different areas and at the same time, alternating. If the muscles are weak, this mechanism does not occur and pain arises.
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