I would get your OH to see his doctor Catembi. I have been doing a bit of research on arthritis myself and have talked to my neighbor who was diagnosed with severe arthritis at 27 (he is now 65).
For many people, like my mum, for example, a simple tablet like Anadin Joint Pain works really well but most over the counter NSAIDS can’t penetrate deep enough to affect the inflammation and Goldenstar is right in the fact that it is often trial and error and you can hit the right combination that works or not. My neighbor tried many different sorts until a combination of two specific drugs removed most of his pain and inflammation and he could walk again. Individually, however, they did nothing at all.
GS is also right in that you shouldn’t leave arthritic inflammation and pain as more damage will occur. It’s not something that gets better so you have to limit it getting worse.
Ref cannabis oil… good to try this, it can work well but my BIL got quite depressed on it although it did help him a lot physically. Worth noting that there are probably many different types of oil out there to try.

He must always ask for something to protect his stomach too or buy a gastro protect product over the counter even if he is just taking ibuprofen, there are a few good ones. I take Pantoprazole 20mg.