What is "synostosis"

Synostosis \Syn`os*to"sis\, n. [NL.] Same as Synosteosis.

n. (context medicine English) The abnormal development of a joint.

Synostosis (plural: synostoses) is fusion of two bones. It can be normal in puberty, fusion of the epiphysis, or abnormal. When synostosis is abnormal it is a type of dysostosis.

Examples of synostoses include:

• craniosynostosis – an abnormal fusion of two or more cranial bones;
• radioulnar synostosis – the abnormal fusion of the radius and ulna bones of the forearm;
• tarsal coalition – a failure to separately form all seven bones of the tarsus (the hind part of the foot) resulting in an amalgamation of two bones; and
• syndactyly – the abnormal fusion of neighboring digits.

Synostosis within joints can cause ankylosis.