Human anatomy

The navicular bone is one of 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...

, found in the 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...

. Its name derives from the bone's resemblance to a small boat, caused by the strongly concave proximal articular surface

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

. The term navicular bone or hand navicular bone was formerly used for the scaphoid bone

Scaphoid bone

The scaphoid bone is one of the carpal bones of the wrist. It is situated between the hand and forearm on the thumb-side of the wrist . The scaphoid bone is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward...

, one of the carpal bone

Carpus

In tetrapods, the carpus is the sole cluster of bones in the wrist between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers , whereas those of the metacarpus do. The corresponding part of the foot is the tarsus...

s of the wrist

Wrist

In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...

.

It is located on the medial side of the 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...

, and articulates proximally with the talus

Talus bone

-External links:* *...

, distally with the three cuneiform bones, and occasionally laterally with the cuboid.

As the bones in the foot develop, a particular process is important for the navicular structure. In the early stage, the navicular bone is actually cartilaginous and has to progress and calcify in order to maintain a strong form. There is a condition, however, in which the three cuneiforms that compose the bone do not completely calcify as a unit. In other words, they do not fuse properly, which leads to the most medial third creating a protrusion along the medial arch. This extension of the foot has a tendency to put stress on two tendons and the ligament that run along its side. The tendon of the peroneus brevis muscle which is the most distal of the two tendons, the tendon of the peroneus longus muscle which extends to the posterior of the ankle, and the posterior talofibular ligament which extends upward partway along the calf muscle, can all be potentially affected by this protrusion. Sometimes referred to as an extra navicular bone, this bump can cause wear and tear on the tendons causing sharp pain with increased activity. This condition can be corrected with surgery to file down or remove the protrusion and repair the tendons that were affected.

Horse anatomy

The navicular bone of the horse, also known as the distal sesamoid bone

Sesamoid bone

In anatomy, a sesamoid bone is a bone embedded within a tendon.Sesamoids are found in locations where a tendon passes over a joint, such as the hand, knee, and foot. Functionally, they act to protect the tendon and to increase its mechanical effect. The presence of the sesamoid bone holds the...

, lies on the palmar

Palmar

Palmar may refer to:* a directional anatomical term of location* El Palmar de Troya, a small village near Utrera, in Andalusia, Spain* Palmar Sur , a town the Osa region, Puntarenas province, Costa Rica...

 aspect of the coffin joint

Equine forelimb anatomy

The equine forelimb of the horse is attached to the trunk of the animal by purely muscular connections...

 between the second phalanx

Phalanx bones

In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...

 and third phalanx, known as the coffin or pedal bone. It is an important structure in relation to lameness and is involved with a significant disease process called Navicular Disease

Navicular Disease

Navicular Disease is a soundness problem in horses, more accurately called "navicular syndrome" as opposed to "disease." It most commonly describes an inflammation or degeneration of the navicular bone and its surrounding tissues, usually on the front feet...

. Recently much of the original literature concerning navicular disease has been called into question, particularly the significance of some radiographic changes.

See also

• Bone terminology
• Terms for anatomical location
• Equine forelimb anatomy
  Equine forelimb anatomy
  The equine forelimb of the horse is attached to the trunk of the animal by purely muscular connections...