Actually 41 Arthritis is more common than you think. I had my first knee surgery due to OA at 24 and while I was at the hospital, I met 13 years old who had her knee surgery due to OA as well...
They say many diseases now getting younger and younger, Arthritis one of them.
At age 12 I was diagnosed with JRA and guess what? At the Doctors office I met young kids, in wheel chairs not able to walk with a lot of damages to their bodies from JRA...
So as you see, 41 is the age!
Our spinal changes start at age 25, so by age 41 you could have some changes in that area as well. Being fit doesn't really matter much, I was very fit and active all my life and after surgically fixing one joint, another one was on a way. lol
Keep your spirits up!