Search for the "destabilizer". What is that? Cat’s are experts with coping and hiding things. When I have a cat who has been dealing with an ongoing issue for years, and then suddenly gets worse, what I want to know is what new thing has popped up to destabilize his ability to cope with the that issue. That’s the first place my mind goes, especially with a condition like arthritis which tends not to be an “end stage” issue at 11 years of age.
We know he has been arthritic chronically, but now he has taken a turn for the worse - a lot worse if euthanasia is being considered as an option. If I was trying to avoid euthanasia, then I'm trying to Sherlock Holmes (let's go out of the box, and examine more than what is presented to us) the underlying issue that piled on top of his plate to make his arthritis even worse. I make that assumption from the beginning, and only suspecting the arthritis as the sole reason for his dire straits unless proven otherwise. So it’s not that the arthritis isn't playing it’s part in making him not feel good, it’s just that to explain what is happening with arthritis alone would not be my first way of thinking about his condition. I know...I'm repeating myself...but I feel strongly about that and I want you to have the best chance with Poetoe.
Find this issue, and you have hope! Make the new issue better, and the idea is that the arthritis stabilizes. Why is this true? Back in my research days we talked about energy budgets and stress in vertebrate animals (fish to be specific ...I worked with a lot of rainbow trout). What this means is that the more your energy and resources go into one thing, the less you have to deal with something else.
If you are in a situation where you can do some bloodwork / xrays or a urinalysis on him, then go for it. All of it at the same time if you can because he is running out of time. I cannot tell you how many times a new thing pops up, and robs them of their prior stability. I know...I'm repeating myself again. Treat the new thing, and they have a chance at doing well. He could have a femoral head that doesn't want to be in there anymore. He could have uremia and is nauseous, so extra wobbly. Hi pancreas might be upset, and the discomfort in his abdomen makes it harder to deal with moving around on arthritic joints. Even a urinary tract infection can make a cat with multiple issues look temporarily horrible. I just treated a great little kitty with this exact same issue the past 48 hours...and she went home last night stronger, eating, and looking much better after being too weak to walk properly.
Let’s say you do that, and it ends up that it really is advanced arthritis that is causing him to suffer. I do in fact see this in practice, but it’s not very common for arthritis in cats to do this alone. You should see something positive with the Onsior by day 3 (an anti-inflammatory and pain reliever). If you didn't, I'm less likely to use a similar medication like metacam, and more likely to Sherlock Holmesyour kitty as to why it didn't work.
If those sort of diagnostics are not available, then consider neural pain. It can make them look worse over time, and they are not responding that well to NSAIDS like Metacam or Onsior alone. You want to discuss with your vet other possibilities like gabapentin or buprenorphine, like I did for Zack. A long acting injection that will give him some relief and buy you some time. And the time we buy is to see if we can stabilize him, get him eating, drinking and stronger. There are other options, especially with helping him long term, but I typically start with those.