The anterior tibiofibular ligament is a band of dense, fibrous connective tissue linking the tibia and fibula bones in the lower leg. Alternately known as the anterior inferior tibiofibular ligament (AITFL), which refers to the fact that it links the two bones at their lowest points, this ligament holds the tibia and fibula together just above the ankle. It also functions to maintain the structure of the joint found here, known as the ankle syndesmosis.
One of several ligaments surrounding the ankle syndesmosis, the anterior tibiofibular ligament is found on the anterior or front side. It attaches on one end to the lateral or inside margin of the tibia, and then crosses diagonally in front of the syndesmosis to attach at its lower end to the medial or inside margin of the fibula, widening as it descends. Adjacent structures include the tendon of the peroneus tertius, which passes anterior to the AITFL as it enters the foot, and the aponeurosis of the lower leg, a tendinous sheath that also lies anterior to this ligament. Behind the anterior tibiofibular ligament are the interosseous ligament, which runs between the two bones, and the cartilage of the talus, an irregularly shaped bone in the foot that forms part of the ankle joint.
The key function of the anterior tibiofibular ligament is to stabilize the ankle syndesmosis by holding the bones together at the joint. A syndesmosis is a type of amphiarthrosis joint that permits very little movement between the adjacent bones; the presence of an interosseous ligament holding the joint together is an identifying characteristic. Like the interosseous ligament and the other ligaments of the ankle syndesmosis — the posterior inferior tibiofibular ligament (PITFL) and transverse ligament — the AITFL maintains the joint. It is, however, in a relatively vulnerable location, and as such it is susceptible to a type of injury known as a high ankle sprain.
While the ankle joint itself allows a great deal of movement, the syndesmosis above it does not. This means that the rigid ligaments around it can be more easily damaged by excessive forces at the ankle. For example, when the ankle joint is bent beyond its normal range of motion, a sprain or even a tear in the anterior tibiofibular ligament or other ligaments can occur.
Mild syndesmosis injury may involve the sprain of a single ligament. More severe injuries can involve damage to multiple ligaments at once, or even the separating of the bones at the joint, known as diastasis. Orthopedists report a frequency of such injuries in athletes like football players and snow skiers, injuries that occur when the foot is bent outward at the ankle joint and that often are misdiagnosed as an ankle sprain. The result of such an injury is a joint that is unstable and in some cases may require surgery to repair the ligament damage.