A horse hoof is the lower extremity of each leg of a horse, the part that makes contact with the ground and carries the weight of the animal. It is both hard and flexible. It is a complex structure surrounding the distal phalanx of the 3rd digit (digit III of the basic pentadactyl limb of vertebrates, evolved into a single weight-bearing digit in horses) of each of the four limbs, which is covered by soft tissue and keratinised (cornified) matter. Anatomy The hoof is made up of two parts. The outer part, called the hoof capsule, is composed of various cornified specialized structures. The inner, living part of the hoof, is made up of soft tissues and bone. The cornified material of the hoof capsule differ in structure and properties. Dorsally, it covers, protects, and supports P3 (also known as the coffin bone, pedal bone, or PIII). Palmarly/plantarly, it covers and protects specialised soft tissues, such as tendons, ligaments, fibro-fatty and/or fibrocartilaginous tissues, and cartilage. The upper, almost circular limit of the hoof capsule is the coronet (also called coronary band), is at an angle to the ground of roughly similar magnitude in each pair of feet (i.e., fronts and backs). These angles may differ slightly from one horse to another, but not markedly. The walls of the hoof originate from the coronet band. Walls are longer in the dorsal portion of the hoof (toe), intermediate in length in the lateral portion (quarter), and short in the palmar/plantar portion (heel). Heels are separated by an elastic, resilient structure named the 'frog'. In the palmar/plantar part of the foot, above the heels and the frog, there are two oval bulges named the 'bulbs'. When viewed from the lower surface, the hoof wall's free margin encircles most of the hoof. The triangular frog occupies the center area. Lateral to the frog are two grooves, deeper in their posterior portion, named 'collateral grooves'. At the heels, the palmar/plantar portions of the walls bend inward sharply, following the external surface of the collateral grooves to form the bars. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating keratinised material, called the 'sole'. Just below the coronet, the walls are covered for about an inch by a cornified, opaque 'periople' material. In the palmar/plantar part of the hoof, the periople is thicker and