A boot (10) for enclosing a foot of a quadruped up to, but not including, a carpal or tarsal joint (32), made generally of a first flexible material (14) with a slit (16) forming an opening for inserting the foot. A lower portion of the first flexible material forms a toe box (20). An upper portion of the toe box is formed of a second flexible material (12A, 12B) that is more elastic than the first flexible material, such as an elastic fabric. The elastic fabric allows the toes to flex downward at the end of each step, then pulls them upward to prevent them from curling under the foot on the next step. An upper retainer (16) may be provided on an upward extension strap (15). The upper retainer loops around the leg above the carpal or tarsal joint (32) to provide vertical retention of the boot.