The tibialis anterior tendon is the elastic band of connective tissue that attaches the tibialis anterior, a muscle of the shin, to the top of the foot. Originating just above the ankle on the front surface of the lower leg, the tendon of the tibialis anterior lies close to the skin. It also lies nearer to the side of the ankle on which the big toe is located. The tibialis anterior tendon is what allows the muscle to perform its functions at the ankle joint and below the ankle at the subtalar joint. These include dorsiflexion, or the act of hinging the foot upward so that the toes are pulled toward the shin, and inversion, or rolling the foot sideways so that the sole of the foot points inward.
As the largest muscle of the shin, the tibialis anterior is the most powerful dorsiflexor of the ankle joint. It arises from the lateral condyle of the tibia, which is found just below and to the outside of the knee joint, and below that from the topmost two-thirds of the anterolateral surface of tibia bone, which is the side facing the adjacent fibula bone. With fibers running vertically down the center of the shin and the muscle body crossing slightly towards the medial side of the leg, this muscle forms the tibialis anterior tendon in the center of the lower shin.
From here the tibialis anterior tendon crosses the front of the ankle joint, angling toward the big toe. It is visible beneath the skin as a narrow band extending over the anterior surface of the ankle toward the medial side and is particularly observable upon dorsiflexing the ankle. On its course across the ankle joint the tendon passes beneath two horizontal, band-shaped ligaments. The higher of the two is known as the superior extensor retinaculum or transverse crural ligament. It is found just above the joint and holds in place the tendons of the muscles of the shin as they enter the foot. Just beneath the ankle joint is the inferior extensor retinaculum or cruciate crural ligament, which similarly binds these tendons to the foot.
After passing under the inferior extensor retinaculum, the tibialis anterior tendon runs a short distance along the medial side of the foot. It then attaches to the underside of the medial aspect of the cuneiform bone, one of the clustered bones of the tarsus in the hindfoot. A portion of the tendon also inserts along the proximal or near end of the first metatarsal, the long bone of the midfoot that approaches the base of the big toe.
