Otosclerosis is a condition that affects the bones in the middle ear, particularly the stapes bone. This bone becomes fixed in place due to abnormal bone growth, which can lead to hearing loss. The condition often develops gradually and is more common in young adults, especially women. The exact cause of otosclerosis is not fully understood, but it may have a genetic component. Symptoms typically include difficulty hearing low sounds and a sensation of fullness in the ear. Treatment options include hearing aids or surgery to restore movement of the stapes bone.