Distal Forelimb of the Horse
The limbs of the horse display extreme adaptations for fast running, support and shock absorption. As
the forelimbs carry 55-60% of the resting body weight (a horse can weigh 500kg), these need to be
very strong.
The skeleton of the distal forelimb comprises of the metacarpel bones and the proximal, middle and
distal phalanges.
The Distal Phalynx
The distal phanlyx (known as the coffin bone) conforms to the hoof interior. It is wedge shaped, sharp
dorsally and to the sides, and blunt proximally and at the back. The dorsal surface is convex from side
to side and lies against the dermis that unites it to the inner surface of the hoof wall. Digital arteries
and nerves pass through a groove in the palmer process.
The palmar surface is slightly concave so that the domed side of the hoof can fit. The palmar border is
extended by a narrow articular zone for the navicular bone; which articulates with both major bones of
the joint.
The Navicular Bone
The distal articular surface of the coffin bone (distal phalyx) is enlarged by a bone called the navicular
bone.
This bone is boat shaped with a convex distal border and a straight proximal border. Dorsally, the
navicular bone contacts the middle phalyx, and a narrow distal facet touches the distal phalynx. The
palmar surface faces the wide tendon of the deep flexor, providing it with a further bearing surface as it
bends towards the semi lunar chest on the undersurface of the distal phalynx.