I have had two cats on Metacam post-surgery. It worked very well. Over the very long term it can damage the liver. Depending on Zingo's age and the dose he gets, it might be very good for him. Ask your vet about the long-term effects and whether they are a concern in Zingo's case.
I hope you can try it for a while and it will give feisty Zingo a good run up the stairs!
"You can say any foolish thing to a dog, and the dog will give you a look that says, 'Wow, you're right! I never would've thought of that!'" -- Dave Barry