Otosclerosis immobilizes the ossicles at the:

Otosclerosis is a condition characterized by abnormal bone growth in the middle ear, which primarily affects the stapes bone. The stapes, one of the three ossicles in the ear, is responsible for transmitting sound vibrations from the middle ear to the inner ear. In otosclerosis, the stapes footplate becomes immobilized due to the abnormal bone growth, leading to conductive hearing loss as sound cannot effectively pass through the ossicular chain.

When the footplate is fixed in place, it cannot move as it should during sound vibrations, thus inhibiting the transmission of sound waves into the cochlea. This immobilization is a key feature of otosclerosis and is central to the condition's pathophysiology. Understanding the mechanics of this immobilization is crucial for grasping the impact of otosclerosis on hearing function.

Other choices, such as the incudostapedial joint or the tympanic membrane, do not directly relate to the primary site of immobilization in otosclerosis, which specifically involves the stapes footplate. Cholesteatoma is a different condition that can affect the ear, but it is not the focus of the immobilization associated with otosclerosis.