I do not have arthritis but only a few years younger. I know their are many on this site that do the workouts with chronic illness and post surgery. I personally decided to listen to my body and don't' push it beyond a pain threshold (not talking about doms but pain) If a workout is causing you pain then its time IMO to find a different form of exercise. My example was chronic tendois with bursa sac rupture (potential future cartilage depletion ) of the ankle from 25 +years of running. I didn't want to push to the point of needing surgery and you can bet those that do push are going to be in even more pain as they age. I also am a good canadate for future arthritis in those ankles
I think you can "customize" cathe workouts to fit what works for your body. I do low impact aerobic - no air jack or anything that is going to put my joints through more pain, sweeling or possible tendon rupture. I also just feel pain if I use a barbell on my upper back/neck area. I use proper form but it still hurts. I figure its just not something my neck back like. I use dumbbells and get a great workout.
I think you just need a new mindset. Yes you can keep working out and you will stay fit but its just going to look different. I absolutely could still do everyone of Cathe workouts even the IMAX stuff but I'm not going to continue to damage my body just because I still can. I will occasionally just do a full on Cathe level workout no modification and then have the swollen ankle joints to show - stop with the ego I'm 44 and plan on being independent mobile till 90+ which means taking care of the body God gave me.
Good luck, don't give up find the exercises that don't put your body in pain. It may be cathe at a slower pace. I love the weight workouts but sometimes my body says slower is better. I will pause the video and do the same rep count but at my speed. Give yourself some grace, go slower, do more breaks and find what works for your body.
post on the discussion forum and some of the regular with health issue can give you more "how to idea"