As footcare professionals know, the angle formed by the bony column of the phalanges with the hoof wall is referred to as the hoof-pastern axis (HPA), and is considered ideal when the dorsal surface of the hoof is parallel to the alignment of the digital bones (Figure 1).¹

The concept of an optimal HPA has a long history in farriery. I can vividly remember standing on the plank floor of the barn when I learned hoof care from my uncle. Although my uncle had no formal training as a horseshoer, this point had been passed down through the generations to him. Alignment of the HPA has been an objective of farriers and veterinarians for centuries.²

Why A Straight HPA Is Important

From what we know historically and empirically, forces at the toe, medial and lateral heels collectively are the lowest when the hoof and pastern angles are aligned.³ Misalignment of the digital bones is seen in 72.8% of horses with a forelimb lameness.⁴

The broken-back HPA is common among horses with a long toe and low heel and the broken-forward is associated with a clubfoot conformation. In one study, 72% of horses had a broken-back HPA and 8% had a broken-forward HPA.⁵ The low (broken-back) HPA is associated with problems related to the navicular apparatus, superficial flexor tendon, deep digital flexor tendon (DDFT) and…