The Extensor Digitorum Longus (EDL) is a muscle located in the lower leg that contributes to foot and toe movement. Positioned in the front compartment of the leg, it is a long, slender muscle that extends downwards, dividing into tendons that connect to the toes.
Anatomy and Location
The Extensor Digitorum Longus is found in the front part of the lower leg. It originates from the lateral tibial condyle (a bony prominence on the outer shin bone), the upper half of the fibula (the smaller bone parallel to the tibia), and the interosseous membrane (a fibrous sheet connecting these bones).
The muscle descends along the front of the lower leg. As it approaches the ankle, it transitions into four tendons. These tendons pass underneath the superior and inferior extensor retinacula, which hold them in place across the ankle joint. After crossing the ankle, these four tendons spread over the top of the foot, inserting into the middle and distal phalanges (toe bones) of the second through fifth toes. This arrangement means the Extensor Digitorum Longus connects to all toes except the big toe.
Primary Functions
The Extensor Digitorum Longus performs two primary actions. It is a muscle for dorsiflexion of the ankle, which involves lifting the entire foot upwards toward the shin. This action is important for clearing the foot off the ground during walking or running, preventing the toes from dragging.
The muscle also extends the lateral four toes—the second, third, fourth, and fifth toes. This extension occurs at both the metatarsophalangeal joints (where the toes meet the foot) and the interphalangeal joints (within the toes themselves). For instance, when you lift your foot to step over an object, the Extensor Digitorum Longus helps raise your toes.
Common Related Conditions
The Extensor Digitorum Longus can be affected by several conditions, often stemming from overuse or repetitive strain. Tendinitis, or tendinopathy, is a common issue involving irritation or inflammation of the EDL tendons. This condition presents as pain, swelling, and stiffness on the top of the foot or the front of the ankle, which worsens with activity and improves with rest. Overuse in activities like running, jumping, or uphill/downhill training can contribute to this irritation, as can poorly fitting footwear that puts excessive pressure on the tendons.
The muscle can also contribute to anterior shin splints, a generalized term for pain in the front of the lower leg. This overuse injury occurs when the muscles involved in dorsiflexion, including the Extensor Digitorum Longus, are subjected to repetitive stress. Muscle strains or spasms can occur within the EDL itself, often due to sudden increases in activity, muscle imbalances, or poor foot mechanics. Symptoms of a strain include localized pain, muscle tightness, and reduced mobility in the ankle or toes.