Fetlock

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Fetlock joint: the joint between the cannon bone and the pastern TrimmedLeg.jpg
Fetlock joint: the joint between the cannon bone and the pastern

Fetlock is the common name in horses, large animals, and sometimes dogs for the metacarpophalangeal and metatarsophalangeal joints (MCPJ and MTPJ).

Contents

Although it somewhat resembles the human ankle in appearance, the joint is technically more similar to the ball of the foot. In anatomical terms, the hoof corresponds to the toe, rather than the whole foot.

Typical untrimmed tuft of hair on the fetlock of a light, non-draft breed of horse Chestnut horse hoof.JPG
Typical untrimmed tuft of hair on the fetlock of a light, non-draft breed of horse
Detail of feather or feathering that covers the fetlock and hoof, seen on many draft breeds Koeten.JPG
Detail of feather or feathering that covers the fetlock and hoof, seen on many draft breeds

The word fetlock literally means "foot-lock" and refers to the small tuft of hair situated on the rear of the fetlock joint. [1]

"Feather" refers to the particularly long, luxuriant hair growth over the lower leg and fetlock that is characteristic of certain breeds.

Formation

Skeleton of the lower forelimb Equine-dist-forelimb-bones.png
Skeleton of the lower forelimb

A fetlock (a MCPJ or a MTPJ) is formed by the junction of the third metacarpal (in the forelimb) or metatarsal (in the hindlimb) bones, either of which are commonly called the cannon bones, proximad and the proximal phalanx distad, commonly called the pastern bone.

Paired proximal sesamoid bones form the joint with the palmar or plantar distal surface of the third metacarpal or metatarsal bones, and are rigidly fixed to the proximo-palmar or -plantar edge of the proximal phalanx.

As a hinge joint

The fetlock is a hinge joint (ginglymus), allowing flexion and extension, but only allowing minimal rotation, adduction, or abduction.

Anatomy compared to that of humans

While sometimes the fetlock is colloquially referred to as an "ankle", even by horse experts, that terminology is not correct. The fetlock is a metacarpophalangeal joint which corresponds to the human upper knuckle, such as that on the ball of the foot.

Problems with the fetlock

In thoroughbred race horses, the fetlock is involved in roughly 50% of catastrophic racing injuries. [2]

See also

Related Research Articles

Foot Anatomical structure found in vertebrates

The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws or nails.

Sesamoid bone Bone embedded within a tendon or muscle

In anatomy, a sesamoid bone is a bone embedded within a tendon or a muscle. Its name is derived from the Arabic word sesamum, indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be present as a normal variant. The kneecap is the largest sesamoid bone in the body. Sesamoids act like pulleys, providing a smooth surface for tendons to slide over, increasing the tendon's ability to transmit muscular forces.

Metatarsal bones

The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth metatarsal. The metatarsals are analogous to the metacarpal bones of the hand. The lengths of the metatarsal bones in humans are, in descending order: second, third, fourth, fifth and first.

Metacarpal bones

In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist which forms the connection to the forearm. The metacarpal bones are analogous to the metatarsal bones in the foot.

Navicular bone

The navicular bone is a small bone found in the feet of most mammals.

Hock (anatomy)

The hock, or gambrel, is the joint between the tarsal bones and tibia of a digitigrade or unguligrade quadrupedal mammal, such as a horse, cat, or dog. This joint may include articulations between tarsal bones and the fibula in some species, while in others the fibula has been greatly reduced and is only found as a vestigial remnant fused to the distal portion of the tibia. It is the anatomical homologue of the ankle of the human foot. While homologous joints occur in other tetrapods, the term is generally restricted to mammals, particularly long-legged domesticated species.

Phalanx bone Digital bone in the hands and feet of most vertebrates

The phalanges are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.

Palmar interossei muscles

In human anatomy, the palmar or volar interossei are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are smaller than the dorsal interossei of the hand.

Plantar interossei muscles Three muscles located between the metatarsal bones in the foot

In human anatomy, plantar interossei muscles are three muscles located between the metatarsal bones in the foot.

Metacarpophalangeal joint

The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the proximal phalanges. Being condyloid, they allow the movements of flexion, extension, abduction, adduction and circumduction at the joint.

Dorsal interossei of the hand

In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.

Equine anatomy Descriptive scheme

Equine anatomy refers to the gross and microscopic anatomy of horses and other equids, including donkeys, and zebras. While all anatomical features of equids are described in the same terms as for other animals by the International Committee on Veterinary Gross Anatomical Nomenclature in the book Nomina Anatomica Veterinaria, there are many horse-specific colloquial terms used by equestrians.

Osselet is arthritis in the fetlock joint of a horse, caused by trauma. Osselets usually occur in the front legs of the horse, because there is more strain and concussion on the fetlock there than in the hind legs. The arthritis will occur at the joint between the cannon bone and large pastern bone, at the front of the fetlock.

Fifth metatarsal bone

The fifth metatarsal bone is a long bone in the foot, and is palpable along the distal outer edges of the feet. It is the second smallest of the five metatarsal bones. The fifth metatarsal is analogous to the fifth metacarpal bone in the hand

Fourth metatarsal bone

The fourth metatarsal bone is a long bone in the foot. It is smaller in size than the third metatarsal bone and is the third longest of the five metatarsal bones. The fourth metatarsal is analogous to the fourth metacarpal bone in the hand

Third metatarsal bone

The third metatarsal bone is a long bone in the foot. It is the second longest metatarsal. The longest being the second metatarsal. The third metatarsal is analogous to the third metacarpal bone in the hand

Skeletal system of the horse

The skeletal system of the horse has three major functions in the body. It protects vital organs, provides framework, and supports soft parts of the body. Horses typically have 205 bones. The pelvic limb typically contains 19 bones, while the thoracic limb contains 20 bones.

Palmar plate

In the human hand, palmar or volar plates are found in the metacarpophalangeal (MCP) and interphalangeal (IP) joints, where they reinforce the joint capsules, enhance joint stability, and limit hyperextension. The plates of the MCP and IP joints are structurally and functionally similar, except that in the MCP joints they are interconnected by a deep transverse ligament. In the MCP joints, they also indirectly provide stability to the longitudinal palmar arches of the hand. The volar plate of the thumb MCP joint has a transverse longitudinal rectangular shape, shorter than those in the fingers.

In the human foot, the plantar or volar plates are fibrocartilaginous structures found in the metatarsophalangeal (MTP) and interphalangeal (IP) joints. The anatomy and composition of the plantar plates are similar to the palmar plates in the metacarpophalangeal (MCP) and interphalangeal joints in the hand; the proximal origin is thin but the distal insertion is stout. Due to the weight-bearing nature of the human foot, the plantar plates are exposed to extension forces not present in the human hand.

Limbs of the horse Structures made of bones, joints, muscles, tendons, and ligaments

The limbs of the horse are structures made of dozens of bones, joints, muscles, tendons, and ligaments that support the weight of the equine body. They include two apparatuses: the suspensory apparatus, which carries much of the weight, prevents overextension of the joint and absorbs shock, and the stay apparatus, which locks major joints in the limbs, allowing horses to remain standing while relaxed or asleep. The limbs play a major part in the movement of the horse, with the legs performing the functions of absorbing impact, bearing weight, and providing thrust. In general, the majority of the weight is borne by the front legs, while the rear legs provide propulsion. The hooves are also important structures, providing support, traction and shock absorption, and containing structures that provide blood flow through the lower leg. As the horse developed as a cursorial animal, with a primary defense mechanism of running over hard ground, its legs evolved to the long, sturdy, light-weight, one-toed form seen today.

References

  1. Merriam-Webster: fetlock
  2. Marquardt, Lucas. "Is this the death of synthetic racing?" (PDF). thoroughbreddailynews.com. Retrieved 9 August 2016.