generally speaking, around what age can a cat start to get arthritis?& teeth/age (?)

my cat I would say just turned 9. he was 2.5 yrs old when I got him (was a stray that went to the shelter). seems he is having some trouble getting up and I notice a very slight slight difference in his walk (still very active & playful though). Also do you think its poosible he is older then that? isn't it the teeth that make the guess on age? he was only that age with horrible breath and soon after had a teeth cleaning and 3 teeth removed..thoughts?