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:
In the horse, the hock consists of the following bones:
- Talus
- Calcaneus
- Central tarsal bone
- Fused 1st and 2nd tarsal bone
- 3rd tarsal bone
- 4th tarsal bone
- 2nd metatarsal bone
- 3rd metatarsal bone
- 4th metatarsal bone
Equine disease states
- Horses may suffer from "capped hock", which is caused by the creation of a false bursa, a synovial sac beneath the skin. Capped hock is usually caused by 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, 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. 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 is called bog spavin.
- Degenerative joint disease of the tarsometatarsal or distal intertarsal joint is referred to as bone spavin.
- Curb, or tarsal plantar desmitis, is traditionally considered a sprain of the plantar ligament, which runs down the back of the hock, serving functionally as a tension band connecting the calcaneus, the fourth tarsal bone and the fourth metatarsal bone. Recent work has shown that curb can be caused by damage to one of many soft tissue structures in this region.
- Stringhalt
Also see equine conformation
Because the hock takes a great deal of strain in all performance disciplines, correct conformation is essential if the horse is to have a sound and productive working life. Common conformational defects include sickle hocks, post-legged conformation/straight hocks, cow hocks, and bowed hocks. Depending on the use of the horse, some defects may be more acceptable than others.
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 and/or nails.
The leg is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or buttock region. The major bones of the leg are the femur, tibia, and adjacent fibula. The thigh is between the hip and knee, while the calf (rear) and shin (front) are between the knee and foot.
In human anatomy, the fibularis longus is a superficial muscle in the lateral compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body (eversion) and to extend the foot downward away from the body at the ankle.
In the human body, the cuboid bone is one of the seven tarsal bones of the foot.
The metatarsal bones or metatarsus are a group of five long bones in the midfoot, located between the tarsal bones and the phalanges (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. A bovine hind leg has two metatarsals.
The ankle, the talocrural region or the jumping bone (informal) is the area where the foot and the leg meet. The ankle includes three joints: the ankle joint proper or talocrural joint, the subtalar joint, and the inferior tibiofibular joint. The movements produced at this joint are dorsiflexion and plantarflexion of the foot. In common usage, the term ankle refers exclusively to the ankle region. In medical terminology, "ankle" can refer broadly to the region or specifically to the talocrural joint.
An epiphysis is one of the rounded ends or tips of a long bone that ossify from a secondary center of ossification. Between the epiphysis and diaphysis lies the metaphysis, including the epiphyseal plate. At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal plate, known as subchondral bone. In evolution, reptiles do not have epiphyses and diaphyses, being restricted to mammals.
In humans and many other primates, the calcaneus or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock.
The navicular bone is a small bone found in the feet of most mammals.
In the human body, the tarsus is a cluster of seven articulating bones in each foot situated between the lower end of the tibia and the fibula of the lower leg and the metatarsus. It is made up of the midfoot and hindfoot.
The tibialis posterior muscle is the most central of all the leg muscles, and is located in the deep posterior compartment of the leg. It is the key stabilizing muscle of the lower leg.
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 lateral plantar pouches. Bog spavin is generally an indication of underlying pathology within the joint.
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.
The talus, talus bone, astragalus, or ankle bone is one of the group of foot bones known as the tarsus. The tarsus forms the lower part of the ankle joint. It transmits the entire weight of the body from the lower legs to the foot.
In the anatomy of humans and many other mammals, the tibiotarsal joint is the joint between the tibia and the tarsus.
The skeletal system of the horse is a skeletal system of a horse that 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.
Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.
Plantar ligament refer to ligaments in the sole of the foot:
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 plantar hock region. Curb is a useful descriptive term when describing swelling in this area.
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.
