The hock, or gambrel, is the joint between the tarsal bones

Tarsus (skeleton)

In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...

 and tibia

Tibia

The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

 of a digitigrade

Digitigrade

A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...

 or unguligrade quadrupedal mammal, such as a 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...

, cat

Cat

The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

, or 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...

. This joint may include articulations between tarsal bones and the fibula in some species (such as cats), 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 (as in horses). It is the anatomical homologue

Homology (biology)

Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 of the ankle

Ankle

The ankle joint is formed where the foot and the leg meet. The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot...

 of the human foot

Foot

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...

. While homologous joints occur in other tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

s, the term is generally restricted to mammals, particularly long-legged domesticated species.

Horse

Although the tarsus refers specifically to the bones and joints of the hock, most people working with horses refer to the hock in such a way to include the bones, joints, and soft tissue of the area. The hock is especially important in equine anatomy, due to the great strain it receives when the horse is worked. Jumping, and movements that require collection, are some of the more stressful activities.

Primary joints and bones of the hock

In the horse, the hock consists of multiple joints, namely:

• Tibiotarsal or tarsocrural joint
• Proximal intertarsal joint or talocalcanealcentroquartal joint
• Distal intertarsal joint or centrodistal joint
• Tarsometatarsal joint
• Talocalcaneal joint

In the horse, the hock consists of the following bones

• Talus
  Talus bone
  -External links:* *...
  
  
• Calcaneus
• Central tarsal
  Tarsus (skeleton)
  In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
  
   bone
• 3rd tarsal bone
• 3rd metatarsal bone
• 4th tarsal bone
• Fused 1st and 2nd tarsal bone

Equine disease states

• Horses may suffer from "capped hock", which is caused by the creation of a false 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...
  
  , a synovial
  Synovial
  Synovial may refer to:* Synovial fluid* Synovial joint* Synovial membrane...
  
   sac beneath the skin. Capped hock is usually caused by trauma
  Blunt trauma
  In medical terminology, blunt trauma, blunt injury, non-penetrating trauma or blunt force trauma refers to a type of physical trauma caused to a body part, either by impact, injury or physical attack; the latter usually being referred to as blunt force trauma...
  
   such as kicking or slipping when attempting to stand. In the absence of a wound, it does not require immediate veterinary attention and is usually only of cosmetic significance. On the other hand, a wound into the calcanean bursa is a serious problem. A capped hock is extremely unlikely to be a cause of lameness
  Lameness (equine)
  Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...
  
  , even if severe.

• Osteochondrosis dissecans, or OCD is a developmental defect in the cartilage or of cartilage and bone seen in particular locations on the surface of the tarsocrural joint. This condition is typically discovered when the horse is young, and is one cause of bog spavin
  Bog spavin
  Bog Spavin is a swelling of the tibiotarsal joint of the horse's hock which, in itself, does not cause lameness. The joint becomes distended by excess synovial fluid and/or thickened synovial tissue bringing about a soft, fluctuant swelling on the front of the joint, as well as in the medial and...
  
  . After surgery to remove bone and cartilage fragments most horses can return to full work.

• Distension of the tibiotarsal joint with excessive joint fluid and/or synovium
  Synovium
  Synovial membrane is the soft tissue found between the articular capsule and the joint cavity of synovial joints....
  
   is called bog spavin
  Bog spavin
  Bog Spavin is a swelling of the tibiotarsal joint of the horse's hock which, in itself, does not cause lameness. The joint becomes distended by excess synovial fluid and/or thickened synovial tissue bringing about a soft, fluctuant swelling on the front of the joint, as well as in the medial and...
  
  .

• Degenerative joint disease of the tarsometatarsal or distal intertarsal joint is referred to as bone spavin
  Bone spavin
  Bone spavin is a bony growth within the lower hock joint of horse or cattle. It is caused by osteoarthritis, and the degree of lameness that results can be serious enough to end a horse's competitive career.-Description of bone spavin:...
  
  .

• Curb
  Curb (horse)
  Curb is defined in older literature as enlargement secondary to inflammation and thickening of the long plantar ligament in horses. However, with the widespread use of diagnostic ultrasonography in equine medicine, curb has been redefined as a collection of soft tissue injuries of the distal...
  
  , or tarsal plantar desmitis, is traditionally considered a sprain of the plantar ligament
  Plantar ligament
  Plantar ligament refer to ligaments in the sole of the foot:* Plantar plates, fibrocartilaginous structures in the metatarsophalangeal and interphalangeal joints of the toes.* One of several tarsal, metatarsal, and tarsometatarsal ligaments:...
  
  , which runs down the back of the hock, serving functionally as a tension band connecting the calcaneus, the fourth tarsal bone and the fourth metatatarsal bone. Recent work has shown that curb can be caused by damage to one of many soft tissue structures in this region.

• Stringhalt
  Stringhalt
  Stringhalt is a sudden flexion of one or both hind legs in the horse, most easily seen while the horse is walking or trotting. It is most evident when the horse is backing up slowly, turning on the affected leg, or suddenly frightened. It involves one or both hind limbs of the horse...
  
  

Conformational defects

Also see equine 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...

Because the hock takes a great deal of strain in all performance disciplines, correct 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...

 is essential if the horse is to have a sound and productive working life. Common conformational defects include sickle hocks

Sickle-hocked

Sickle-hocked is the technical term used to describe a specific type of incorrect leg structure in animals. The back leg joints of an animal, usually a horse or other equine mammal, are set with too much angle, resulting in the hock also being excessively angled. This can result in uneven hoof...

, post-legged

Post-legged

Post legged is when the joints in an animal are not set correctly. When an animal is post-legged, the leg joints are far too straight, with almost no bend in the legs. Four-legged animals must have some bend in the hocks, otherwise the hooves would wear unevenly, and this may result in lameness, or...

 conformation/straight hocks, cow hocks

Cow-hocked

Cow-hocked is the condition in a livestock animal where the back leg joints of the animal are set incorrectly. This term is used to describe when the back 'knee' on an animal is set inward, resulting in a splayed look in the back legs. This can result in the uneven wearing of hooves, which can end...

, and bowed hocks. Depending on the use of the horse, some defects may be more acceptable than others.