Osteomata  are bony tumors which generally arise by growth of the periosteum, and form solid bony masses external to the cortex of the bone, when they are called exostoses.

The density of the bone composing the tumor varies a great deal, some being very hard and ivorylike, while others are like the cellular marrow of the long bones.

Osteomata may be surrounded by a layer of fibrous periosteum or, in certain cases, beneath the periosteum appears a layer of cartilage producing the so-called exostosis cartilaginea. The latter formation is the one which is most common in the vicinity of the epiphyseal line of the long bones, notably of the leg.

Osteomata form circumscribed hard nodular masses of bony consistency, and are usually painless. They may cause interference with function from their size, especially when they appear in close connection with a joint.

Treatment  is complete and thorough removal.