McClure, Robert C.

University of Missouri: MOspace

A horse’s hoof is composed of the wall, sole andfrog. The wall is simply that part of the hoof that is visi-ble when the horse is standing. It covers the front andsides of the third phalanx, or coffin bone. The wall ismade up of the toe (front), quarters (sides) and heel.When the foot is lifted off the ground, the sole andfrog are visible, as well as the bars of the wall and thecollateral grooves (see Figure 1).The wall of the hoof is composed of a horny materialthat is produced continuously and must be worn off ortrimmed off. The hoof wall does not contain bloodvessels or nerves. In the front feet, the wall is thickest atthe toe; in the hind feet the hoof wall is of a moreuniform thickness. The wall, bars and frog are theweight-bearing structures of the foot. Normally the soledoes not contact the ground.Inside the hoof, lateral cartilages extend back and upfrom the inner and outer sides of the third phalanx(Figure 2a). These cartilages are flexible, but as the horseages, they are usually ossified and replaced by bone.Between the second and third phalanges and above thedeep flexor muscle tendon is a small bone called thenavicular bone (Figure 2b). The navicular bone and itsassociated bursa — a fluid-filled sac that reduces frictionbetween the tendon and the bone — are involved innavicular disease, which is a common cause of lameness.The digital cushion is a mass of flexible material thatcontributes to the formation of the heels (see Figure 3).This structure is one of the primary shock absorbers ofthe foot.As weight is placed on the hoof, pressure is trans-mitted through the phalanges to the wall and onto the$.25 G 2740 Printed with soy ink on recycled paperMU GuideAGRICULTURALPUBLISHED BY MU EXTENSION, UNIVERSITY OF MISSOURI-COLUMBIA muextension.missouri.edu/xplor/HorsesFunctional Anatomy of the Horse FootRobert C. McClureDepartment of Veterinary Anatomy, College of Veterinary MedicineCentralgrooveof frogCollateralgrooveSoleWhite lineWallBar of wallAngle of wallFrogFigure 1. The wall, bars and frog are the weight-bearing struc-tures of the foot.3rd phalanx(coffin bone)LateralcartilageTendon ofdeep digital flexorNavicular boneNavicular bursaCoronetToe Quarter Heel2nd phalanxFigure 2. Internal and external structure of the horse foot.a bcArchive vrsion -- See extension.missouri.edudigital cushion and frog. The frog, a highly elasticwedge-shaped mass, normally makes contact with theground first. The frog presses up on the digital cushion,which flattens and is forced outward against the lateralcartilages. The frog also is flattened and tends to pushthe bars of the wall apart (Figure 3). When the foot islifted, the frog and other flexible structures of the footreturn to their original position.When the foot is placed on the ground, blood isforced from the foot to the leg by the increase in pressureand by the change in shape of thedigital cushion and the frog. Thepressure and the change in shapecompress the veins in the foot.When the foot is lifted, the com-pression is relieved and bloodflows into the veins again. In thisway, the movement of these struc-tures in the hoof acts as a pump.Exercise increases the blood circu-lation in the foot and favors goodhoof growth. Lack of exercise,dryness of the horny wall, andpoor nutrition inhibit hoof growth.Normally, the hoof wall growsat the rate of about three-eighthsinch per month. New layers ofhoof wall are produced continu-ously from just below an areacalled the coronet at the junction ofthe skin and the hoof wall (seeFigure 2c).The hoof wall is covered withmaterial that prevents evaporation of moisture. Whenthis material is deficient, the hoof wall becomes dry andexcessive flaking and cracking may occur. A good hoofpaint aids in preventing excessive drying.This publication was originally written jointly by Robert C.McClure, Gerald R. Kirk and Phillip D. Garrett. Kirk and Garrettare former faculty members in the Department of VeterinaryAnatomy, College of Veterinary Medicine. Illlustrations are byPhillip D. Garrett.Page 2 G 2740 Reviewed and reprinted 10/99/5M Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department ofAgriculture. Ronald J. Turner, Director, Cooperative Extension, University of Missouri and Lincoln University, Columbia, MO 65211. UniversityOutreach and Extension does not discriminate on the basis of race, color, national origin, sex, religion, age, disability or status as a Vietnamera veteran in employment or programs.  If you have special needs as addressed by the Americans with Disabilities Act and need this publicationin an alternative format, write ADA Officer, Extension and Agricultural Information, 1-98 Agriculture Building, Columbia, MO 65211, or call(573) 882-7216. Reasonable efforts will be made to accommodate your special needs.OUTREACH & EXTENSIONUNIVERSITY OF MISSOURICOLUMBIAWeight of horseFoot is liftedDigital cushion expandsWalls of hoof contractWalls of hoofexpand slightlyDigital cushionis flattenedFigure 3. Flexible structures in the horse’s hoof expand and contract with each step as weightis transferred from one foot to another.

Functional anatomy of the horse foot (1999)

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