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CHAPTER

Functional Anatomy of the

Equine Musculoskeletal System

AnnA Dee FAils

ANATOMIC NOMENCLATURE AND USAGE Foot
Veterinary medical anatomists have been using the The foot consists of the hoof and all it encloses: the
Nomina Anatomica Veterinaria, created by the Inter­ connective tissue corium (dermis), digital cushion, distal
national Committee on Veterinary Gross Anatomical phalanx (coffin bone), most of the cartilages of the distal
Nomenclature since 1968 to standardize the names of phalanx, distal interphalangeal (coffin) joint, distal part
anatomical structures. This chapter endeavors to use the of the middle phalanx (short pastern bone), distal sesa­
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most current, correct terms as outlined in that publication. moid (navicular) bone, podotrochlear bursa (navicular
Nonetheless, equine practitioners need to be equally fluent bursa), several ligaments, tendons of insertion of the
in older terminology, which is likely to be in wide usage common digital extensor and deep digital flexor mus­
among horse owners and equine professionals. This chap­ cles, blood vessels, and nerves. Skin between the heels is
ter will provide useful and common synonyms for many also part of the foot.
structures, along with their more technically correct terms.
Figure 1.1 provides the directional terms for veteri­
nary anatomy that will be used in this chapter. With the Hoof Wall, Sole, and frog
exception of the ocular and oral cavity structures, the The hoof is continuous with the epidermis at the cor­
terms anterior, posterior, superior, and inferior are not onet, and the underlying corium of the hoof is likewise
applicable to quadrupeds. continuous with the dermis of the skin. The ground sur­
face of the hoof comprises the sole, frog, heels, bars, and
ground surface of the wall (Figure 1.3). The ground sur­
face of the forefoot is normally larger and rounder than
THORACIC LIMB that of the hindfoot, reflecting the corresponding shape

Digit and Fetlock of the distal surface of the distal phalanx (coffin bone).
The hoof wall extends from the coronary band (also
The digit is composed of distal (third), middle (sec­ called the coronet), the transition between skin and hoof,
ond), and proximal (first) phalanges and associated distad to the ground. The surface of the wall is divided into
structures (Figure 1.2). The fetlock consists of the meta­ the toe, medial and lateral quarters, and heels (Figures 1.3
carpophalangeal (fetlock) joint and the structures sur­ and 1.4). From the toe, where it is thickest, the wall
rounding it. Because the digits and fetlocks of the becomes progressively thinner and more elastic toward the
thoracic limb and the pelvic limb are similar in most heels, where it thickens again when it reflects to become
respects, the following descriptions pertain to both limbs the bars. Ranges for the angle of the toe between the dorsal
unless otherwise indicated. When referring to structures surface of the hoof wall and the ground surface of the hoof
of the forelimb, the term “palmar” is used; this will obvi­ vary widely. 1,16 In the ideal digit, the dorsal surface of the
ously be replaced with “plantar” when referring to the hoof wall and the dorsal surface of the pastern should be
hindlimb. Likewise, such terms as metacarpophalangeal parallel, reflecting the axial alignment of the phalanges.
and metatarsophalangeal are counterparts in fore‐ and The vascular and densely innervated collagenous con­
hindlimbs, respectively. nective tissue deep to the hoof is the corium. The corium

Adams and Stashak’s Lameness in Horses, Seventh Edition. Edited by Gary M. Baxter.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/baxter/lameness
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