Having dealt with this for while, I will lay out some experiences and you can interpolate them for your situation as needed. i have some additional hand injury in addition to arthritis so what I need may be different for you. For me, I do not have a problem with knobs and dials, in fact, a large easy to manipulate knob or dial can be easier and less painful than a small button or constant pressing, which is actually more painful on the my bad days where fine motor control is a dream. On a bad day, I have to limit what I do with the iPad. For me camera weight is an issue with any prolonged use because of the strain on hands. My hands are fairly large. By controls I mean aperture, shutter speed, and loading film mainly.
Canon A-1 -> grip +, weight +, controls are meh, because of how they are executed except film loading which is good
Canon FTB QL -> grip is iffy, but good deal otherwise if serviced and lubed
Nikon F3 -> grip -, with MD-4 way too heavy, controls + except rewinding film
Leica R4-> grip ok, with winder feels like it puts odd stresses on hand and wrist
Leicaflex SL -> the odd shape makes it easy to hold which mitigates the weight issue somewhat (that was a surprise), controls are really easy to manipulate - the shutter wheel is surprisingly easy, the 2-cam lenses are really heavy though
Olympus OM 1&2 -> these are my favorites as aperture and shutter are in a line and large control so less stress on the hands overall, with a case the grip is good (my preferred) or with an empty winder (no batteries) which allows a large grip with virtually no weight gain - however, the film rewind button which is not great best of days is a really nasty on the bad ones.
You may also find that the throw on lenses matters. The Leica R have a long throw which means more turning of the lens when focusing which can be painful in itself at times. Hope some of that is useful.