This is a disgrace? Have they referred you to occupational health? If not, why not? I’m pretty sure arthritis is covered under the equality act 2010.
“The 2010 Equality Act (Disability Discrimination Act in Northern Ireland) makes it unlawful for employers to treat anyone with arthritis or a related condition less favourably than anyone who doesn't have that condition, in these key areas:“
If it was me I would be putting in a grievance stating that I believe I’m being discrimated because of my disability and that I feel that the business are trying to make me quit because of it. I’d mention in the grievance if this goes to tribunal it could be seen as constructive dismissal if I’m forced to leave.
I’d also put a bullying and haresment form in, demand that it’s heard as bullying and harassment and NOT a grievance as they’re always so so keen to downgrade it to a grievance.
Get your area health and safety rep on this ASAP, phone your branch if you can’t get hold of them. If you can’t get through phone higher up until you get answers.
I’d also recommend emailing MOYa at firstname.lastname@example.org
asking for why managers deem it ok to treat staff in such a way