RA & OA in both knees


I’m struggling to walk and do day to day housework, I work in a school sorting out exams (setting up, sorting out the entire running of them) I’m afraid I’m not going to be able to do my job, my employers know I have RA but I feel they don’t take it serious, if I can’t do my job how do I address it? I need a knee op but they said I’m young for it, nearly 55 but my quality of life us suffering, thanks