An Excerpt From ...

EQUINE PHOTOS & DRAWINGS FOR
CONFORMATION & ANATOMY

Equine Stay Apparatus

The stay apparatus is a system of muscles, tendons, and ligaments in the horse's leg. It works together with the suspensory apparatus to allow the horse to "lock" its lower leg joints with no muscular effort. This mechanism makes it possible for the horse to sleep while standing. The structures involved are:

• biceps brachii tendons (both origin and insertion)
• lacertus fibrosis tendon
• radial carpal extensor tendon
• common digital extensor tendon
• serratus ventralis muscle (thoracic portion)
• triceps muscle (long head)
• SDFT and superior check ligament
• DDFT and inferior check ligament
• suspensory ligament and its branches
• distal sesamoidean ligaments

Illustration by Sherrie Engler

Except for the lacertus fibrosis tendon, all of these structures are described earlier in this chapter. The lacertus fibrosis is a long tendinous band through the biceps brachii and the fascia (connective tissue) of the forearm. It ends by merging with the radial carpal extensor tendon. Its function is to assist the stay apparatus by stabilizing the knee, keeping it from buckling forward.

These structures work together to hold the legs in a normal standing position. For example, the serratus ventralis muscle supports the horse's body weight, which would normally flex the shoulder. But the biceps brachii tendons and the triceps muscle prevent this action by extending it. The SDFT and DDFT help by fixing the elbow joint. Of course, the bones from the elbow to the fetlock are situated in a more-or-less straight line, so it takes very little effort (by the lacertus fibrosis) to stabilize them. The fetlock joint, however, is under the constant heavy strain created by the horse's body weight. The suspensory apparatus, as part of the stay apparatus, holds it securely in the normal standing position.

Also explained in this chapter:

• The role of the forelegs in locomotion.
• Why a long, sloping shoulder is important for every type horse.
• The often-overlooked upper arm.
• How elbow conformation affects the entire foreleg.
• What a "well-directed" forearm means, precisely.
• Knees, knees, and more knees.
• What "good bone" means and how to measure it.
• Ideal fetlock and pastern angles for riding horses.

And that's just the conformation! In the anatomy section, we explore how it all works . . .

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Equine Photos & Drawings for
Conformation & Anatomy!

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