Horse arm conformation covers the horses humerus and radius and the arm bone is from the point of shoulder to the elbow, and its length dictates how tightly the elbow and lower joints can bend and reach for extension.

The long horse arm bone

The humerus is long when it is 50-60% of the length of the scapula. The elbow is beneath the middle of the withers if the humerus is long.

This conformation mostly affects jumping, steeplechase, eventing, lateral movements of dressage, and cutting.

A long humerus increases movement of elbow away from torso, both forward and to the side, allowing more tucking over fences and increased stride in speed events. It provides a scaffold for lengthy muscle attachments of flexor and extensor muscles, which contract with greater force to increase power and speed.

Best suited for speed events, jumping, and dressage.

The short horse arm bone

The humerus is usually in a horizontal position which closes the shoulder angle (shoulder and humerus) to less than 90 degrees.

Common, usually seen in Quarter Horses, Paints, and Warmbloods

A short humerus decreases the scope of a horse, and contributes to a short, choppy stride. This increases the impact stress on front legs, especially the feet. The rider is jarred and the horse absorbs a lot of concussion. More steps are needed to cover ground, increasing the chance of front-end lameness.

The horse tends to be less able to do lateral movements.

Good for sprinting sports and the horse is best used for pleasure riding, non-impact activities, and sprinting sports like roping or barrel racing.

The Horses Forearm (radius)

Long forearm

The length of the radius (between elbow and carpus) is long

Seen in all breeds, especially Thoroughbreds, Saddlebreds, Tennessee Walkers, Arabians, and Warmbloods.

A long forearm is desirable for any performance activity, especially if the horse also has a short cannon. It increases the surface area and length of muscular attachments to gain the best leverage for maximum stride length and speed.

Good muscling of a long forearm is especially advantageous to jumping horses, as the strong forearm muscles absorb concussion from the impact and diffuse the strain on tendons and joints on landing.

A long forearm is best for speed events, jumping events, and long distance trail riding

Short forearm

The distance of radius from elbow and carpus is proportionately short

Uncommon, but it is seen in Morgans and Quarter Horses.

A short forearm affects speed and jumping events, has little effect on stock horse events.

The length of stride is dependent on the forearm length and shoulder angle, so a short forearm causes the horse to increase the number of steps to cover a distance, increasing overall muscular effort and speeding up fatigue.

A short forearm increases the action of the knees, giving an animated appearance. Knee action is not compatible with speed.

A horse with a short forearm is best for showing, hunter equitation, harness or parade.