Deafness can occur for many reasons. use your knowledge of the structure of the ear and the process of detecting sound, to propose a mechanism for how arthritis could cause deafness.

Arthritis results when synovial joints are damaged and can no longer move freely. the joints between the ossicles, found in the middle ear, are synovial joints. if they became stiff from arthritis and their movements were limited, sound waves striking the tympanic membrane would not be efficiently transferred to the oval window of the cochlea. without that transmission, the fluid in the cochlea cannot move the hair cells on the organ of corti. if those hair cells do not move, no impulses relaying information about sound can be generated.

~potters6/te801/biology/biounits/respiration.htm

An egg, or a sack of flour