The invention relates to an ankle joint orthosis which comprises a shank, which extends from the heel across the ankle and is open across the tibia, a sole element connected to said shank, and a first and second strap for fastening the orthosis to the lower leg and foot, characterized in that: the shank (1) and the sole element (2) each have an inflexible portion (1a, 2a) and a flexible portion (1b, 2b), the inflexible sole portion (2a) extending from the heel to the arch and the flexible sole portion (2b) extending at least from the arch in the direction of the toes the first strap (3) is fastened to the distal edge of the flexible shank portion (1b), the second strap (4) is fastened to the distal end of the inflexible sole portion (2a) and a third strap (5) is fastened to said distal end. The three straps (3, 4, 5) can be guided transversely in front of the lower leg, across the instep and around the inner and outer malleolus or around the foot.
