Your doctor determined from your last set of X-Rays that you have arthritis in your spine. Now you're concerned with how it got there. Was it the physical stress of your job? The 15 years of league bowling? Or maybe the accident you had when you were a teenager? It's hard to tell.
When it comes to arthritis the underlying cause isn't necessarily what you DID, but more what you HAVEN'T BEEN DOING. Do you maximize the range of motion in your body every day? Do you regularly have your spine checked for Subluxations? Joints wear down faster when they're stuck and misaligned - that's why it's important to keep them lined up and moving with regularly spaced Chiropractic care.
Blaming the activities in your life for your arthritis is like blaming the sidewalk for scuffing your shoes. Things naturally wear down when you use them over time, including your spine. Instead of worrying about the wear and tear you have, start doing something NOW to slow the process. Getting adjusted more often is a good place to start.