My cat has had a number of problems with her limbs over the years, including fractured kneecaps. She is now 10, and noticeably cautious in jumping. She can't jump much higher then the seat of a dining chair. Over the summer there were several occasions when she appeared to be limping, which improved with rest. I imagine she is quite likely to develop arthritis, and wondered if there is anything I could add to her diet to help ward this off?