Otosclerosis is a hereditary bone disorder of the inner ear, unique to the temporal bone (the bone that houses the ear) and known to affect only human beings. It is among the most common causes of acquired hearing loss. The most common clinical manifestation is a conductive hearing loss as a result of fixation of the stapes bone (the third and smallest hearing bone). The other symptoms may be tinnitus and dizziness. In some cases, it can cause permanent hearing loss. It usually affects both ears and is also more common in females.

Treatment options include the use of a hearing aid or microsurgery called a stapedotomy, in which the fixed stapes bone is replaced with a piston.