- A cartilage-capped bony projection arising from any bone that develops from cartilage. SEE ALSO: osteochondroma. SYN: hyperostosis (2), poroma (2). [exo- + G. osteon, bone, + -osis, condition]- e. bursata an e. arising from the joint surface of a bone and covered with cartilage and a synovial sac.- hereditary multiple exostoses [MIM*133700] a disturbance of enchondral bone growth in which multiple, generally benign osteochondromas of long bones appear during childhood, commonly with shortening of the radius and fibula; the skull is not involved; the ill effects are usually mechanical but malignant change is rare; autosomal dominant inheritance with genetic heterogeneity of which some cases are due to mutation in the e.-1 gene (EXT1) on 8q. SYN: hereditary deforming chondrodystrophy (1), multiple e., osteochondromatosis.- subungual e. painful osseous outgrowths that elevate the nail of the great toe or fingers in young people.
* * *ex·os·to·sis .ek-(.)säs-'tō-səs n, pl -to·ses -.sēz a spur or bony outgrowth from a bone or the root of a toothex·os·tot·ic -'tät-ik adj
* * *n.a benign outgrowth of bone with a cap of cartilage, arising from the surface of a bone. See osteoma.
* * *ex·os·to·sis (ek″sos-toґsis) [ex- + ostosis] 1. a benign bony growth projecting outward from the surface of a bone. 2. osteochondroma.
Exostosis at the metatarsocuneiform joint.
Medical dictionary. 2011.