The withers is the ridge between the shoulder blades of a four-legged animal. In many species it is the tallest point of the body, and in horses and dogs it is the standard place to measure the animal's height (in contrast, cattle

Cattle

Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

 are normally measured to the top of the hips).

Horses

The withers in horse

Horse

The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s are formed by the dorsal spinal processes of roughly the 3rd through 11th thoracic vertebrae

Thoracic vertebrae

In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper...

 (most horses have 18 thoracic vertebrae), which are unusually long in this area. The processes at the withers can be more than 12 inches (30.5 cm) long.

Since they do not move relative to the ground (as the horse's head does), the withers are used as the measuring point for the height of a horse. Horses are commonly measured in hands – one hand is 4 inches (10.2 cm). Horse heights are extremely variable, from small pony breeds to large draft breeds. The height at the withers of an average Thoroughbred

Thoroughbred

The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...

 is 16 hands (1.6 m), and ponies

Pony

A pony is a small horse . Depending on context, a pony may be a horse that is under an approximate or exact height at the withers, or a small horse with a specific conformation and temperament. There are many different breeds...

 are up to 14.2 hands (1.44 m).

Conformational issues

The withers of the horse are considered in evaluating conformation. Generally, a horse should have well-defined withers, as they are considered an important attachment point for the muscles of the torso. Withers of medium height are preferred, as high withers make it difficult to fit a saddle and are often associated with a narrow chest, and low withers (known as "mutton withers") do not provide a ridge to help keep the saddle in place.

More importantly, the dorsal spinal processes provide an attachment for the muscles that support the shoulder and neck. Horses do not have a clavicle

Clavicle

In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...

, so the shoulder can freely rotate backwards. If the vertebrae of the withers are long (front to back), the shoulder is more free to move backwards. This allows for an increase of stride length (and so it can increase the horse's speed). It is also important in jumping, as the shoulder must rotate back for the horse to make his forearm more parallel to the ground, which will then raise the animal's knees upward and get the lower legs out of the way. Therefore, the withers have a direct impact on one of the most important points of conformation

Equine conformation

Equine conformation evaluates the degree of correctness of a horse's bone structure, musculature, and its body proportions in relation to each other. Undesirable conformation can limit the ability to perform a specific task. Although there are several universal "faults," a horse's conformation is...

: the shoulder.

Dogs

In dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s, the height of the withers is often used to determine the dog's jump height in various dog sports. It is also often a determining factor in whether the dog conforms to the show-quality standards

Breed standard

A breed standard in animal fancy and animal husbandry is a set of guidelines which is used to ensure that the animals produced by a breeder or breeding facility conform to the specifics of the breed....

 for its breed.

Medical problems

Inflammation of the bursa

Bursa (anatomy)

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement...

e (bursitis

Bursitis

Bursitis is the inflammation of one or more bursae of synovial fluid in the body. The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone. Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless...

) in this region is called fistulous withers.