Plural form; people who suffer from arthritis, or relating to multiple cases of arthritis.
From 'arthritic' (relating to arthritis) + '-s' (plural). While less commonly used than 'arthritis' as a noun, it can refer to patients or multiple instances of the condition.
It's interesting that we rarely say 'arthritics' as a noun for people with arthritis, preferring 'arthritis patients'—language often avoids turning medical conditions into labels for people themselves, though some people embrace it as part of their identity.
Complete word intelligence in one call. Free tier — 50 lookups/day.