oseteo-arthritis?

[rahul_vs85]

My Mother recently came to know that she is suffering from osteo-arthritis.Today she heard a crack sound around the left knee while she is getting down from a bike.Later she used some pain killer to get rid of the severe pain. Does the crack sound mean any breakage in the bones ?? Is there any possibility for the breakage in osteo-arthritis patients? plzz reply soon...