I find the vomiting a bit concerning - I had an old boy (11+) who began limping intermittently too, and I also thought arthritis (maybe it was too) - he lived on wet food morning and evening with Hills Senior in a bowl for whenever he wanted, and his huge water bowl full of fresh water. He started upchucking and appearing tired and weak, and when I took him to be examined he turned out to have massive kidney problems - the one had completely atrophied and the other was barely functioning, and after a few days in hospital we had to make the sad choice.
In hindsight I realised that the limping could in fact have been caused by pain or discomfort from his kidneys. I think you should perhaps have your kittties examined to rule out kidney problems - this can be done with a blood test and/or ultrasound - probably the blood test, it shows up creatinine levels.
I have to also mention that this boy a) was knocked by a car once, which did affect his hip although no fractures, he never was a good jumper, which made me first think arthritis and b) he did survive a kidney infection so bad that the vet gave him up and told me to take him home and expect the worst - he barely ate for a week and then miraculously started eating again and went from strength to strength, and survived about another 4 years. He also had to have a blind eye removed a few months before the final sickness, and we did take blood tests for kidney before and after, and I was warned that anaesthetic does not do kidneys any good. Shame, he really went through the mill, that one!