What Are the Causes of Subchondral Bone Pain in the Fetlock?

In both sport horses and racehorses, fetlock osseous pathology is a relatively frequent cause of pain. While fetlock bone injury has long been recognised as a clinical problem in racehorses (including trotters), we are now increasingly recognising osseous pathology in the fetlock joint of more elite sport horses as a clinical problem. As greater demands are put on sport horses, the more similarity is seen between the osseous injuries detected in sport horses and racehorses. These greater demands include increased speed in endurance horses, increased extravagance of dressage horses and repetitive hyperextension in showjumping horses.

Although osseous pain is frequently referred to as subchondral bone pain, bone pain can derive from both the subchondral bone plate and underlying trabecular bone, so it is important to consider both structures as a potential source of pain. Pain may relate to joint damage and associated bone damage, or to bone damage that is not related to primary articular surface damage. The locations that appear at highest risk of bone damage are in the plane of the sagittal ridge of the proximal phalanx, particularly towards the dorsal aspect, and the palmar aspect of the parasagittal groove of the third metacarpal/metatarsal condyles, the dorsal aspect of the third metacarpal/metatarsal sagittal ridge, and the axial metacarpal condyles. […]