An athletic leg brace apparatus of the type operable to be connected to the sides of a ski boot wherein the apparatus includes a first and second lower leg brace member and a first and second upper leg brace member. Each of the first upper and lower leg brace members and the second upper and lower leg brace members are connected by a ball joint hinge structure which preferably includes nested hemispherical shell members which are connected to respective portions of the leg brace members by a laterally extending axle positioned coaxially through the center of the hemispherical shells. A front portion of the first and second lower leg brace members and the first and second upper brace members are connected by a rigid semicylindrical member while the rear portion of the first and second lower brace members and the first and second upper leg brace members are interconnected by a flexible, adjustable connecting means. The lowermost portions of each of the first and second lower leg brace members are operable to be releasably connected to an upper lateral portion of a ski boot. The instant athletic leg brace apparatus permits an unemcumbered forward and rearward flexture of a skiers leg while concomitantly serving to restrict the lateral flexture of a skiers upper and lower leg portions and to transmit lateral forces on the skiers legs into the lateral portions of the skiers boot and ultimately the edges of the skiers skis for heightened performance characteristics.