An interosseous membrane binds the tibia and fibula throughout their length and separates the muscles on the front from those on the back of the leg (Fig. 16-12A). The interosseous membrane forms a “Y” proximally to surround the upper tibiofibular joint, the anterior division being called the anterosuperior tibiofibular ligament and the posterior division being called the posterosuperior tibiofibular ligament (Fig. 16-12A, B). A similar arrangement is formed below, where the interosseous membrane thickens and divides to surround the inferior tibiofibular syndesmosis (Fig. 16-12A, C). The two components are called the anteroinferior and posteroinferior tibiofibular ligaments.