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The extensor digitorum longus (EDL) is a muscle in the anterior (extensor) compartment of the leg. It is one of four muscles in this compartment, the others being the tibialis anterior, extensor hallucis longus, and peroneus (fibularis) tertius. The EDL is the most lateral muscle in the anterior compartment and originates from the tibia and fibula bones. The EDL muscle has a range of functions, including extending the toes and dorsiflexion of the foot and ankle. The muscle is also associated with certain medical conditions, such as Charcot-Marie-Tooth disease and postpolio syndrome.
| Characteristics | Values |
|---|---|
| Name | Extensor Digitorum Longus |
| Other Names | EDL Muscle, Extensor Digitorum Longus Muscle |
| Location | Lateral part of the front of the leg |
| Compartment | Anterior (extensor) |
| Muscle Type | Feather-like, unipennate, pennate |
| Function | Extends toes, dorsiflexes foot at the ankle joint, everts the foot |
| Innervation | Deep peroneal nerve, deep fibular nerve |
| Blood Supply | Anterior tibial artery, fibular artery |
| Conditions | Charcot-Marie-Tooth disease, postpolio syndrome, Duchenne muscular dystrophy |
| Related Procedures | Hibbs tenosuspension, Hibbs tendon transfer |
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What You'll Learn
The EDL is a pennate muscle situated at the front of the leg
The extensor digitorum longus (EDL) muscle is a pennate muscle situated at the front of the leg. It is one of four muscles in the anterior compartment of the lower leg, alongside the tibialis anterior, extensor hallucis longus, and peroneus (fibularis) tertius. The EDL is the most lateral muscle in the anterior compartment, originating from the lateral condyle of the tibia and the upper three-quarters of the anterior surface of the body of the fibula.
The EDL muscle plays a crucial role in ankle dorsiflexion, as it crosses the dorsal aspect of the ankle joint. Additionally, it crosses the subtalar, metatarsophalangeal, and interphalangeal joints of the foot, allowing it to evert the foot and extend the toes. The tendon of the EDL passes under the superior and inferior extensor retinaculum at the anterior surface of the ankle joint before reaching its distal insertion.
The EDL is classified as an unipennate muscle because all the muscle fibres attach to one side of the tendon. Within the inferior extensor retinaculum, the tendon splits into four smaller tendons that are wrapped in a synovial sheath. These tendons then diverge towards the toes, forming the triangular dorsal digital expansions or extensor hoods.
The EDL muscle is innervated by the deep peroneal nerve, a branch of the common peroneal nerve. In terms of blood supply, the proximal part of the EDL is supplied by the anterior tibial artery, while the distal part receives blood from the fibular artery.
The EDL muscle is commonly associated with certain medical conditions, such as Charcot-Marie-Tooth disease and postpolio syndrome. It is also relevant in procedures like the Hibbs tenosuspension, which is beneficial in preventing the overpull of the tibialis anterior tendon in patients with diabetes or rheumatoid arthritis.
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It is one of four muscles in the anterior compartment of the lower leg
The extensor digitorum longus (EDL) muscle is one of four muscles in the anterior (extensor) compartment of the lower leg. The other three muscles in this compartment are the tibialis anterior, extensor hallucis longus, and peroneus (fibularis) tertius. The EDL is the most lateral muscle in the anterior compartment.
The EDL muscle originates on the anterior tibia, specifically from the lateral condyle of the tibia. It runs down the front of the tibia, anterior to the ankle joint, and is deep to the extensor retinaculum. The tendon of the EDL passes under the superior and inferior extensor retinaculum before reaching its distal insertion. Within the inferior extensor retinaculum, the tendon splits into four smaller tendons that are wrapped in a synovial sheath. These four tendons then diverge towards the toes.
The EDL muscle is involved in the extension of the toes and dorsiflexion of the foot at the ankle joint. It also everts the foot as it crosses the subtalar, metatarsophalangeal, and interphalangeal joints. The muscle is innervated by the deep peroneal nerve, a branch of the common peroneal nerve. The leg portion of the muscle receives its blood supply from the anterior tibial artery and the fibular artery.
The EDL muscle is a unipennate muscle, as all the muscle fibres attach to one side of the tendon. It is also classified as a fast-twitch muscle based on its myosin expression pattern. The function and properties of the EDL muscle can be evaluated through various protocols, including stretching, stimulation at different resting tensions, and ex vivo testing using the Aurora Scientific in vitro muscle test system.
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The EDL is involved in dorsiflexion of the foot
The extensor digitorum longus (EDL) muscle is a pennate muscle situated at the lateral part of the front of the leg. It originates on the anterior tibia and runs down the front of the tibia, anterior to the ankle joint and deep to the extensor retinaculum. The EDL is involved in dorsiflexion of the foot, which is the upward movement of the foot that reduces the angle between the foot and the shin. This movement occurs exclusively at the ankle joint and is important during the gait cycle, as it lifts the foot and toes to prevent them from dragging on the ground.
Dorsiflexion of the foot is facilitated by the muscles in the anterior compartment of the leg, including the EDL, tibialis anterior, extensor hallucis longus, and fibularis tertius. The EDL helps to dorsiflex the foot by producing dorsiflexion of approximately -18° to -6°. This range of motion is important for maintaining a normal gait and preventing the foot from dragging during walking.
The contractile and passive properties of the EDL muscle can be measured ex vivo using the Aurora Scientific in vitro muscle test system. This involves subjecting the EDL muscle to a six-step stretching protocol where the muscle is strained to 160% Lo with increments of 10% Lo. The viscous property of the EDL muscle can be evaluated by measuring the stress relaxation rate (SRR) at different time frames after stretching and holding the muscle at 10% Lo.
The EDL muscle is also involved in extending the toes, and its function can be assessed clinically by measuring its activity during the gait of patients with equinus and equinovarus foot deviations (EVFD). Weakness or injury to the EDL muscle can result in a condition called foot drop, where there is a significant weakness of ankle and toe dorsiflexion. This can lead to an equinovarus deformity, also known as steppage gait, where the patient walks with an exaggerated flexion of the hip and knee to compensate for the weakness in dorsiflexion.
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It is innervated by the deep fibular nerve
The extensor digitorum longus (EDL) muscle is one of four muscles in the anterior compartment of the lower leg. The other muscles in this compartment include the tibialis anterior, extensor hallucis longus, and peroneus (fibularis) tertius. The EDL is the most lateral muscle in the anterior compartment.
The EDL is a pennate muscle, situated at the lateral part of the front of the leg. It arises from the lateral condyle of the tibia, from the upper three-quarters of the anterior surface of the body of the fibula, and from the upper part of the interosseous membrane, among other structures. The muscle passes under the superior and inferior extensor retinaculum of the foot and divides into four slips, which run forward on the dorsum of the foot and are inserted into the second, third, and fourth phalanges of the four lesser toes.
The EDL plays a role in extending the toes and dorsiflexing the foot at the ankle joint. It also everts the foot and extends the toes by crossing the subtalar, metatarsophalangeal, and interphalangeal joints of the foot. The function of the EDL can be assessed by dorsiflexing toes 2-5 against resistance.
The EDL is innervated by the deep fibular nerve (L5, S1), also known as the deep peroneal nerve, which is a branch of the common fibular nerve. The leg portion of the muscle receives its blood supply from two arteries: the proximal part is supplied by the anterior tibial artery, while the distal part receives blood from the fibular artery.
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The EDL is a fast-twitch muscle
The extensor digitorum longus (EDL) muscle is a fast-twitch muscle. It is situated at the lateral part of the front of the leg, originating on the anterior tibia and running down the front of the tibia anterior to the ankle joint. The EDL muscle is responsible for extending toes and dorsiflexing the foot at the ankle joint.
EDL muscles are composed almost entirely of fast glycolytic and fast oxidative fibres. They are characterised by their myosin heavy chain isoform profiles, which can be analysed using Next Generation Sequencing tools. These tools allow for a more precise characterisation of differences among fibre types, including distinguishing between different isoforms of specific proteins.
The fast-twitch nature of the EDL muscle has been demonstrated in studies examining the effects of creatine incubation on muscle performance. Creatine supplementation has been shown to improve force production and twitch kinetics in fatigued EDL muscles. During repetitive fatiguing stimulation, creatine-treated EDL muscles exhibited improved performance, taking significantly longer to lose half of their original force compared to control muscles.
The EDL muscle has also been used in studies investigating muscle function and contractile properties. For example, the EDL muscle has been subjected to stretching protocols and analysed for stress-strain profiles and viscous properties. Additionally, the EDL muscle has been stimulated at different resting tensions to determine the optimal length for maximum twitch tension.
In summary, the EDL muscle is a fast-twitch muscle with unique molecular characteristics and contractile properties. It plays a crucial role in extending toes and dorsiflexing the foot, and its function can be enhanced through creatine supplementation.
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Frequently asked questions
EDL stands for Extensor Digitorum Longus.
The EDL is located in the anterior (extensor) compartment of the leg.
The EDL extends the toes and dorsiflexes the foot at the ankle joint.
The EDL is used to extend the lateral four digits and dorsiflex the ankle.
The EDL is composed of muscle fibers that are characterized as fast-twitch based on their myosin heavy chain isoform profiles.
