An exostosis, also known as bone spur, is the formation of new

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

on the surface of a bone. Exostoses can cause chronic pain ranging from mild to debilitatingly severe, depending on the shape, size, and location of the lesion. It is most commonly found in places like the ribs, where small bone growths form, but sometimes larger growths can grow on places like the ankles, knees, shoulders, elbows and hips. Very rarely are they on the skull. Exostoses are sometimes shaped like spurs, such as calcaneal spurs. Osteomyelitis, a bone infection, may leave the adjacent bone with exostosis formation. Charcot foot, the neuropathic breakdown of the feet seen primarily in diabetics, can also leave bone spurs that may then become symptomatic. They normally form on the bones of joints, and can grow upwards. For example, if an extra bone formed on the ankle, it might grow up to the shin. When used in the phrases "cartilaginous exostosis" or "osteocartilaginous exostosis", the term is considered synonymous with

osteochondroma Osteochondromas are the most common benign tumors of the bones. The tumors take the form of cartilage-capped bony projections or outgrowth on the surface of bones exostoses. It is characterized as a type of overgrowth that can occur in any bone w ...

. Some sources consider the two terms to mean the same thing even without qualifiers, but this interpretation is not universal.

Osteophytes

Osteophytes are bone spurs that develop on the margins of joints secondary to external stimuli such as

osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the w ...

. However, these are not always distinguished from exostoses in any definite way.

Fossil record

Evidence for exostosis found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. Exostosis has been reported in dinosaur fossils from several species, including ''

Acrocanthosaurus atokensis ''Acrocanthosaurus'' ( ; ) is a genus of carcharodontosaurid dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous, from 113 to 110 million years ago. Like most dinosaur genera, ...

'', ''

Albertosaurus sarcophagus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period, about 71 million years ago. The type species, ''A. sarcophagus'', was app ...

'', '' Allosaurus fragilis'', ''

Gorgosaurus libratus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Can ...

'', and ''

Poekilopleuron bucklandii ''Poekilopleuron'' (meaning "varied ribs") is a genus of tetanuran dinosaur, which lived during the middle Bathonian of the Jurassic, about 168 to 166 million years ago. The genus has been used under many different spelling variants, although on ...

''.

Hereditary multiple exostoses

Hereditary multiple exostoses (HME), also called hereditary multiple osteochondromas (HMO), is a condition that is estimated to affect 1 in 50,000 individuals. Multiple benign or noncancerous bone tumors develop in the affected individuals. The number and location vary among affected patients. Most people seem unaffected at birth; however, by the age of 12 years, they develop multiple exostoses. Affected individuals commonly complain of palpable and recognizable lumps (exostoses) at about the knees and in the forearms. The condition characteristically occurs bilaterally. It may lead to mild degrees of growth retardation and limb asymmetry. Genu valgum (commonly known as "knock-knees"), ankle valgus, and bowing and shortening of one or both of the forearm bones are common manifestations.

Types

* Buccal exostosis * Footballer's ankle (exotosis of the ankle bone) * Hereditary multiple exostoses (HME) *

Subungual exostosis Subungual exostoses are a type of non-cancerous bone tumor of the chondrogenic type, and consists of bone and cartilage. It usually projects from the upper surface of the big toe underlying the nailbed, giving rise to a painful swelling that des ...

Surfer's ear Surfer's ear is the common name for an exostosis or abnormal bone growth within the ear canal. Surfer's ear is not the same as swimmer's ear, although infection can result as a side effect. Irritation from cold wind and water exposure causes the ...

(exostosis of the ear canal) * Torus mandibularis * Torus palatinus * Calcaneal spur (heel spur)

References

External links