The invention relates to a method for measuring the number of steps of an animal moving on four legs, according to which an acceleration sensor (38, 29) detects acceleration in a plane in which the animal is moving, and wherein the acceleration is caused by the locomotion of the animals' leg. The invention further relates to an apparatus (1) for detecting the distance covered by the animal moving on four legs, comprising a housing (3) and a measuring unit provided within the housing, wherein the measuring unit comprises a step counting unit (22) comprising at least one acceleration sensor (38, 29), wherein the acceleration sensor (38, 29) is arranged inside the housing (3) such that it detects an acceleration substantially parallel to the plane in which the animal is moving. Moreover, the invention relates to a system which comprises an apparatus (1) for detecting the distance covered by an animal moving on four legs and a receiving unit (2), as well as a tendon boot (30) for application to a fetlock of an animal moving on four legs, in particular a horse, wherein the tendon boot (30) has means (33) for fastening the apparatus (1).