Maximus Gage
The human body has more than 600 muscles that help with everything from breathing to giving birth. Some of these muscles are skeletal, some are cardiac, and some are smooth. Smooth muscles line the inside of some organs, including the stomach, and intestines, and are responsible for moving food through the gastrointestinal (GI) tract. This process is called peristalsis and it involves a series of wave-like muscle contractions that move food and fluids forward through the GI tract.
| Characteristics | Values |
|---|---|
| Definition | Inversion is a movement of the foot which causes the soles of the feet to face inwards. |
| Muscles that cause inversion | Tibialis anterior, Tibialis posterior |
| Range of motion | 25° to 30° at the subtalar joint, 8° to 10° at the transverse tarsal joint |
| Injury | Ankle sprain affecting the ligaments on the lateral aspect of the ankle. |
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What You'll Learn
- The tibialis anterior and tibialis posterior muscles cause inversion of the foot
- The peroneus longus and peroneus brevis muscles cause eversion of the foot
- Inversion injuries of the ankle are common and result in sprains
- The foot has two main categories of muscles: extrinsic and intrinsic
- The extensor digitorum longus and extensor hallucis longus muscles cause dorsiflexion of the foot
The tibialis anterior and tibialis posterior muscles cause inversion of the foot
The tibialis anterior and tibialis posterior muscles are vital in controlling the inward movement of the foot, also known as inversion. Inversion is a movement of the foot that causes the soles of the feet to face inwards, with the opposite movement being eversion. The range of motion for inversion of the foot at the subtalar joint ranges from 25° to 30°.
The tibialis anterior muscle is innervated by the deep fibular nerve and the recurrent genicular nerve (L4). It is the largest dorsiflexor of the foot and is responsible for dorsiflexion and inversion of the ankle. When the foot is on the ground, the muscle helps to balance the leg and talus on the other tarsal bones, keeping the leg vertical even when walking on uneven ground. The tibialis anterior also helps to maintain the medial longitudinal arch of the foot and stabilises the ankle as the foot hits the ground during the contact phase of walking.
The tibialis posterior muscle is located deep in the shin or calf area and is responsible for controlling overpronation during the midstance phase of walking. This action is crucial for avoiding excessive pressure on the foot's medial side and for evenly distributing body weight across the metatarsal heads. The tibialis posterior also supports the arch of the foot and plays a critical role in the stability and alignment of the lower leg. It assists in plantar flexion at the ankle joint, a motion that is crucial for pushing off the ground during walking or running.
The tibialis anterior and posterior oppose one another in movement of the foot and ankle. They work in tandem to control foot movements, especially during the toe-off phase in walking or running.
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The peroneus longus and peroneus brevis muscles cause eversion of the foot
The peroneus longus and peroneus brevis muscles are responsible for causing eversion of the foot. Eversion is the movement of the foot that causes the soles of the feet to face outwards, with inversion being the opposite movement.
The peroneus longus, also known as the fibularis longus, is a superficial muscle in the lateral compartment of the leg. It is the longest and most superficial of the three fibularis (peroneus) muscles. The fibularis longus arises from the head and upper two-thirds of the lateral, or outward, surface of the fibula. It then runs down along most of this bone, becoming a tendon that wraps around and behind the lateral malleolus of the ankle. Finally, it continues under the foot to attach to the medial cuneiform and first metatarsal. The fibularis longus is supplied by the superficial fibular nerve.
The peroneus brevis, or fibularis brevis, is a short muscle that lies in the lateral part of the lower leg, deep to the fibularis longus. It is one of three ankle everters, along with the fibularis longus and fibularis tertius. The fibularis brevis originates from the distal two-thirds of the lateral fibula, with its tendon passing downwards and looping posterior to the lateral malleolus. The fibularis brevis inserts on the styloid process at the proximal end of the fifth metatarsal and is supplied by the superficial fibular (peroneal) nerve.
Together, the fibularis/peroneus muscles help to steady the leg upon the foot, especially when standing on one leg. They also play a role in maintaining the transverse arch of the foot.
Injuries to the peroneus longus and brevis muscles can result in pain and swelling at the lateral ankle. These injuries commonly occur during a lateral ankle sprain, with the fibularis brevis tendon being the most frequently dislocated tendon.
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Inversion injuries of the ankle are common and result in sprains
Inversion injuries of the ankle are common and frequently result in sprains. Ankle sprains are injuries to the strong ligaments that support the ankle, causing them to stretch beyond their limits and tear. Inversion sprains are caused by the foot turning inward, which tears the lateral ligaments.
The inversion of the foot is a movement that causes the soles of the feet to face inwards, with the opposite movement being eversion. Inversion occurs primarily at the talocalcaneonavicular joint and the subtalar (or talocalcaneal) joint. The muscles that cause inversion of the foot are the tibialis anterior and tibialis posterior. The range of motion for inversion of the foot at the subtalar joint ranges from 25° to 30°, while it is considerably less at the transverse tarsal joint, ranging from 8° to 10°.
Inversion ankle sprains are the most common injury in sports and athletic activities. They make up about 40% of all sports injuries and 25% of missed practice or play time. Inversion sprains are particularly common because there is a physiological preference for the foot to invert, and the muscles that control eversion prevent excessive inversion.
The most commonly affected ligament in inversion ankle sprains is the anterior talofibular ligament, which accounts for 70-85% of ankle sprains caused by forceful inversion. The calcaneofibular ligament is also frequently torn in inversion sprains. In some cases, the posterior talofibular ligament may also be affected.
The symptoms of an inversion ankle sprain include pain, swelling, and sometimes muscle spasms. The severity of an ankle sprain can vary from mild to severe, depending on the number of ligaments involved and the extent of the tear. Mild sprains may only cause minimal pain and swelling, while moderate to severe sprains can result in significant swelling, bruising, and difficulty walking. Treatment for ankle sprains typically involves protection, rest, ice, compression, and elevation (PRICE), with more severe sprains requiring immobilization and physical therapy. In some cases, surgery may be necessary to repair or reconstruct the injured ligaments.
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The foot has two main categories of muscles: extrinsic and intrinsic
Extrinsic Muscles
The extrinsic muscles arise from the anterior, posterior, and lateral compartments of the leg. These muscles include:
- Tibialis Anterior: This muscle is located alongside the lateral surface of the tibia and is the strongest dorsiflexor of the foot. It originates from the lateral surface of the tibia and attaches to the base of the big toe.
- Tibialis Posterior: The deepest-lying muscle in the posterior compartment, the tibialis posterior originates from the tibia and fibula and attaches to the plantar surfaces of the toes. It inverts and plantarflexes the foot and maintains the arch of the foot.
- Extensor Digitorum Longus: A deep-lying extrinsic muscle that runs the length of the tibia. It originates from the tibia, transitions into a tendon, and attaches to the toes. It is responsible for the extension of the toes and dorsiflexion of the foot.
- Extensor Hallucis Longus: A deep-lying extrinsic muscle beneath the extensor digitorum longus. It originates from the fibula and attaches to the big toe, responsible for its extension and dorsiflexion.
Intrinsic Muscles
The intrinsic foot muscles can be divided into two main groups: plantar and dorsal.
Plantar Muscles
There are ten intrinsic muscles located in the plantar aspect (sole) of the foot. These muscles work as a group to stabilise the foot's arch and control the toes' movements. The plantar muscles include:
- Abductor Hallucis: This muscle is located on the medial side of the sole and contributes to a small soft tissue bulge. It abducts and flexes the great toe.
- Flexor Digitorum Brevis: This muscle is located laterally to the abductor hallucis and is responsible for flexing the lateral four toes.
- Abductor Digiti Minimi: This muscle is located on the lateral side of the foot and is responsible for the abduction and flexion of the little toe.
Dorsal Muscles
The dorsal group consists of two muscles:
- Extensor Digitorum Brevis: This small, thin muscle lies underneath the long extensor tendons of the foot. It is responsible for the extension of the lateral four toes.
- Extensor Hallucis Brevis: Often considered part of the extensor digitorum brevis muscle, this muscle aids in extending the big toe.
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The extensor digitorum longus and extensor hallucis longus muscles cause dorsiflexion of the foot
The extensor digitorum longus and extensor hallucis longus muscles are two of several muscles in the anterior (extensor) compartment of the leg. They are responsible for causing dorsiflexion of the foot.
The extensor digitorum longus (EDL) is a feather-like muscle that extends the lateral four toes at the metatarsophalangeal joint. This muscle is unable to extend the entire length of the toes independently, as the toes remain flexed at the interphalangeal joints. However, when the EDL contracts together with the lumbricals—the main extensors of the interphalangeal joints—it contributes to the extension of every joint between the bones of the lateral four toes. Acting in synergy with the tibialis anterior, extensor hallucis longus, and fibularis tertius, the EDL participates in dorsiflexion of the foot when their proximal attachments are fixed.
The extensor hallucis longus (EHL) is a thin muscle that extends the big toe at both the metatarsophalangeal and interphalangeal joints. This muscle is located between the tibialis anterior and extensor digitorum longus muscles. The EHL is responsible for extending the big toe, but it also has accessory actions in other joints. For example, it assists in the inversion of the foot and dorsiflexion of the ankle.
Both the EDL and EHL muscles cross the dorsal aspect of the ankle joint, contributing to the common function of dorsiflexion of the foot. Dorsiflexion is an important movement for the gait cycle, as it angulates and lifts the foot above the walking surface, allowing for forward movement.
Inversion of the foot is a separate movement that causes the soles of the feet to face inwards, with eversion being the opposite action. The muscles responsible for inversion of the foot include the tibialis anterior and tibialis posterior, while eversion is caused by the peroneus longus and peroneus brevis muscles.
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Frequently asked questions
No muscles invert food. However, muscles in the gastrointestinal tract are involved in the process of digestion.
Food moves through the gastrointestinal tract through a process called peristalsis, which involves wave-like muscle contractions that move food forward through the digestive system.
There are two types of peristalsis: primary peristalsis, which is induced by swallowing, and secondary peristalsis, which is evoked by distension of the esophagus.
The enteric nervous system (ENS) controls the gastrointestinal system independently of the central nervous system (CNS). It releases substances that speed up or delay the movement of food and the production of digestive juices.
The muscles that invert the foot, or turn the sole of the foot inward, include the tibialis posterior, flexor digitorum longus, and flexor hallucis longus.
