Abstract: The ankle joint orthosis includes a U-shaped joint collar having a web of a flexible material proceeding underneath the foot. The joint collar (20) includes two ankle splints (21,121), which are connected by means of a web (22) proceeding below the heel of the foot and, on the rear, while leaving the heel and the attachment of the Achilles tendon uncovered, by a wide band (23) as well as at the front, within its upper ergion, by means of a longitudinally variable belt strap (25,25') and a metatarsal portion (30), which is medially and laterally provided with flaps, which laterally and medially embrace the borders of the foot and constitute the connection for two belt straps (40,140) and a transverse cross strap (50) connecting the flaps. On the side of the sole of the foot, the metatarsal portion (30) is connected with the web (22) of the joint collar (20) by means of a highly flexible web (35) acting as an articulation.