The anterior muscles of the leg
When studying the muscles of the leg, they can be compartmentalized into four primary groups: the anterior, lateral (fibular), superficial posterior, deep posterior compartments. Not only are these groups located within the appropriate aspect of the tibia and fibula, but they are also defined by intermuscular septa and surrounded by the deep fascia of the leg. This article will focus specifically on the muscles in the anterior compartment of the leg as well as any clinical relevance.
The muscles of the anterior leg are located within the anterior compartment of the leg. When observed macroscopically, this is seen as the anterolateral region of the leg. Because of the nature of their origins and insertions and consequently their movements, these muscles are known as the dorsiflexors of the leg.
Origin: Lateral tibial condyle, proximal half of lateral tibial shaft, Interosseous membrane
Insertion: Medial cuneiform bone, Base of metatarsal bone 1
Function: Talocrural Joint: Foot dorsiflexion; Subtalar joint: Foot inversion; Supports medial longitudinal arch of foot
|Extensor hallucis longus||
Origin: (Middle third of ) Medial surface of fibula, Interosseous membrane
Insertion: Base of distal phalanx of great toe
Function: Metatarsophalangeal and interphalangeal joint 1: Toe extension; Talocrural joint: Foot dorsiflexion
|Extensor digitorum longus||
Origin: (Proximal half of) Medial surface of fibula, Lateral tibial condyle, Interosseus membrane
Insertion: Distal and middle phalanges of digits 2-5
Function: Metatarsophalangeal and interphalangeal joints 2-5: Toe extension; Talocrural joint: Foot dorsiflexion; Subtalar joint: Foot inversion
Origin: (Distal third of) Medial surface of fibula
Insertion: Dorsal surface of base of metatarsal bone 5
Function: Talocrural joint: Foot dorsiflexion; Subtalar joint: Foot eversion
Deep fibular nerve (L5, S1)
(branch of the common fibular nerve)
|Vascularization||Anterior tibial artery (branch of the popliteal artery)|
|Clinical relations||Strains, tendon injuries, compartment syndrome, crush syndrome|
This article will discuss the anatomy, function, and clinical importance related to the anterior muscles of the leg.
Anatomy & Function
The muscles found in the anterior compartment of the leg are: the tibialis anterior, extensor hallucis longus, extensor digitorum longus and fibularis tertius muscle.
As previously mentioned, they are dorsiflexors. The reason for this is their origin at specific points on the tibia or fibula and insertion on certain areas of the foot. Because of that, contraction of these muscles will lead to a shortening of the muscle’s body and cause the dorsum of the foot to be pulled towards the leg. This movement is known as dorsiflexion. Also, certain muscles from this group assist in the inversion of the foot.
After reading this article, we recommend you go through these video tutorials where we present the functions of the anterior leg muscles in 3d models!
Tibialis anterior muscle
This muscle is the most anterior and medial of all four anterior leg muscles. It originates from the proximal portion of the leg, precisely, from the lateral tibial condyle and proximal half of the tibial shaft, in addition to the adjacent portion of the interosseous membrane.
In the distal portion of the leg, the muscle fibers converge to form a tendon that extends through the medial side of the foot toward the muscle’s insertion; the medial cuneiform bone (medial and inferior surface), and base of the first metatarsal bone. The main function of this muscle is to dorsiflex the foot, as well as invert it. It also supports the medial longitudinal arch of the foot.
Extensor hallucis longus
The extensor hallucis longus lies lateral to the tibialis anterior muscle and is partially covered by it. It originates from the middle third of the medial surface of the fibula and adjacent interosseous membrane. The tendon of the muscle arises within the distal portion of the leg and is oriented the same way as the body of the muscle - lateral to the tibialis anterior tendon.
The tendon continues its way through the foot by extending over its dorsal surface and finally inserting on the superior surface of the base of the distal phalanx of the hallux. This muscle extends the hallux and dorsiflexes the foot.
Extensor digitorum longus
This muscle is the most posterior and lateral of all the muscles of the anterior leg. Its origin is lateral and above the origin of the extensor digitorum muscle, precisely in the proximal half of the medial surface of the fibula and lateral condyle and shaft of the tibia.
The muscle fibers descend through the anterior compartment of the leg and converge to a tendon before the ankle. The tendon of the muscle extends over the dorsal surface of the foot and divides into four terminal tendons. Each one of these tendons splits into two extensions that insert onto the appropriate middle and distal phalanges of the lateral four toes. This muscle extends the toes and dorsiflexes the foot.
The fibularis tertius muscle is considered to be part of the extensor digitorum longus muscle. It originates inferiorly to the origin of the extensor digitorum longus: along the distal third of the medial surface of the fibula.
The muscle fibers form a tendon in the distal part of the leg which first extends through the dorsal aspect of the foot; then, turns laterally to insert onto the base of the metatarsal bone of the fifth toe (little toe). This muscle assists in both dorsiflexion and eversion of the foot.
Recalling the innervation of the leg, the dominant nerve that gives rise to motor branches in the anterior region of the leg is the common fibular (peroneal) nerve. The specific branch of the common fibular nerve that innervates all muscles of the anterior leg is the deep fibular (peroneal) nerve. The same logic goes with the vascularization - all of these muscles are supplied with blood by a branch of the popliteal artery: the anterior tibial artery.
Various accidents and disasters, such as car crashes or building collapses may cause the affected individuals to be victims of severe wrecks.These wrecks can produce a large pressure on affected body parts, which is most commonly on the legs.
The muscles sustaining high pressure can suffer from ischemia since this process also compresses and occludes the arteries that supply the affected muscles. Upon removal of pressure, blood is re-introduced through the damaged vessels causing exudation of plasma and proteins from outside the arteries. This fluid collects in the extracellular compartment of the muscle which typically causes swelling. As fluid collects in the limited space around the muscles, pressure increases. This state is known as compartment syndrome.
In the more severe of cases, this type of trauma can cause substances from the damaged cells to enter the blood flow. This is dangerous since the main intracellular protein is myoglobin which is very large protein that can clot the kidney’s filtration system and cause acute kidney failure. Also, since the main intracellular cation is potassium, its high concentration after trauma may interfere with the electrolyte balance within the heart and cause acute heart failure. The described scenario is called crush syndrome.
Evidently, compartment and crush syndromes are not the most common clinical conditions that can affect the anterior leg, but are certainly amongst the most dangerous ones. In daily practice, you will most frequently encounter muscle strains which occur due to quick heavy lifting. Also, depending on the stress put upon the muscles, tearing of tendons and/or muscle bodies can occur.