I have a friend who is older and she hates the word elderly. I read that one isn't elderly until the age 75 but my friend and her girlfriends are far from elderly acting. They could run circles around the best of them. I'll never think of her as elderly. Just correct to say senior, or ignore it.
I started having arthritis in my hands at 40 and it bothered me a lot. I didn't know what it was and I though it was because I worked on the computer a lot. One doesn't have to be 'old' to have arthritis.