In 1994, I had a horseback riding accident in which I fractured (in addition to ribs) the glenoid of the right shoulder (the glenoid is where the ball of the humerus fits).
Doctor determined there was no need for medical intervention other than a sling. About a month ago, I did a marathon mopping of my tile floors in anticipation of overnight guests. The next day, my right shoulder was achy. I figured the mopping motion caused it. But I continue to have moderate pain in that shoulder and the upper arm, mostly the pain is in the upper arm. I would think that muscle ache from over-exertion would have resolved by now; could the old fracture be a factor?
Mended bones are never again 100%. Just as scar tissue is never 100%. I have had five broken bones and on occasion, they all bother me.
IIRC it’s called “traumatic arthritis.”
As the others have mentioned, it could be the break that is causing the pain. On the other hand, if you injured or strained your rotator cuff during your marathon mopping, that doesn’t tend to go away very easily on its own. I injured my shoulder playing basketball in grad school and several weeks of taking it easy didn’t help at all. One week of exercises prescribed by a PT though had it feeling as good as new.
My aunt fractured her hip at the age of 10, recovered, and went on to lead a normal, active life.
Until she reached her 70s, that is. The hip problems started with relatively minor stiffness and pain, but got worse over the years. She is now 92 and can still walk, but she needs a walker and can’t go very far.
(BTW, she refused to have any corrective surgery until the pain became severe in her late 80s, and by then other health issues precluded her going under anesthesia. Otherwise, the hip would have been replaced.)
So IANAD, but I would be inclined to think that an old fracture can definitely cause problems at any time in later life.
It was a good thing that I fell and fractured some ribs in 1961. It didn’t take long for them to heal and they did cause me any trouble again until about three years ago when the-pain-from-hell hit those fractures.
My doctor wanted to get an x-ray of my lungs to be sure that it wasn’t something more serious. His nurse reminded him that Medicare required that he x-ray both sides of my lungs.
I had arthritis in the joints near those fractures on the left. But I had pneumonia in the right lung. They caught it early because of the flare up from the old injury.
Lucky me.
The short answer to your specific title question is “yes.” Post-traumatic arthritis can occur years later and certainly might be triggered by vigorous use of the joints. We see this in wight-bearing joints frequently, but also in the back and arms. However in the circumstance you describe several other equally possible diagnoses come to mind. It’s not unusual for an acute shoulder injury to hang on that long; a rotator cuff strain or tear, for instance–it’s not necessarily a flare of the old injury. In addition, non-trauma-related conditions such as adhesive capsulitis can present with persistent pain, limited range of motion and a putative (but probably incorrect) attribution to injury.
The Pedant spent the last year whining about my adhesive capsulitis and sleeping on my good side. There’s a tendency (even for us doctors) to think someone else is so kind as to have our diagnosis if they have similar pain. 
But FWIW shoulder problems present with such protean manifestations that I think a good ortho is necessary to get to the root of the problem unless your primary physician is really sharp with shoulders.
Thanks everyone. I am scheduled to see my PCP soon for a routine check, so I will get her on it.