Works quickly but expensive!
My vet recommended this product for my 16-year-old cat who was struggling to get onto the sofa. He seemed to have more trouble climbing everywhere, but without showing pain or complaining.
One treat every morning, and within a few days, he was going up the stairs quickly and getting onto the sofa easily. It's such a joy to see him in good shape.
The downside: the price (over €1 per treat)!