I merely suggested trying something which has helped other people. Of course there's a lack of clinical data, the drug companies are the ones who fund research and they stand nothing to gain from research into Aloe Vera if it's going to lead to a reduction in the use of their products.
Just did a quick google search, I'd suggest digging deeper yourself but here are a couple showing the anti-inflammatory properties of Aloe which is widely documented if you search further. The basis of treating arthritis with aloe vera is for its anti-inflammatory effects allowing a reduction or...
Have you tried putting Aloe Vera Gel in his drinking water? I've heard of various cases in which it has eased the symptoms of arthritis and the science behind it seems sound. There are some testimonials here: http://www.purelynature.co.uk/animals/animal-testimonials and some companies offer a 60...