Some cats do get moer bony as they age. I have a 13-year-old that is just like a kitten. It might be time for her to have a geriatric blood panel done. They're about $200 where I live, but is a really worthwhile test to do. If anything is starting up you might be able to treat it inexpensively, as opposed to later when it's worse and more expensive.
Maybe a call to the tech at the vet's office would be an idea also.
"Remember that children, marriages, and flower gardens reflect the kind of care they get." -- H. Jackson Brown, Jr.