I'm not a vetenarian, but it seems unlikely that arthritis is a cause of death, unless she could not stand on her legs anymore, and her organs got crushed. But that's also unlikely, because I don't believe an animal who can't get up anymore would keep quiet until she passes away. She would make a lot of noise, and the rest of the herd would panic at least. And according to the spokesman there was nothing special to see on the camaera's. I do think that panic would be considered 'special'.