Having broken both ankles (one in 1974 and the other in 2003), I've learned a thing or three about how my body reacts to exercise vis-à-vis arthritis (not saying my experience will be the same for anybody else).
When I finally got my body running again back in 2009 I found that the day after a run my ankles were so sore I could barely walk, and two days after they were sometimes okay and other times they were even sorer than the day before. Given that I was attempting a strict every-other-day workout program, I would force myself to run even when I could barely walk, and funny thing, after the first (rather painful) half of a mile, the pain usually started easing up, and by a mile it was virtually gone. Last April when I once again restarted running (professional and family issues kept me away from running between early 2010 and last April), I was initially doing only one or two days per week, and my ankle pain was pretty much constant except during my runs and for an hour or two after, and that held true even if I went four or five days between runs. Figuring I had nothing to lose, I started upping my workout frequency to every third day, then every other day, then pretty much every day by late June. Yes, my ankles ALWAYS hurt at the start of every run (now they only hurt on occasion), and yes I looked (and often still look) seriously uncoordinated/silly for the first half mile to mile, but after that they loosen up and away I go. It's kind of cool that now that I'm running somewhere between 60 and 80 miles per week my ankles are actually slightly less painful than they were in my more sedentary days before 2009.
Kind of as a side note on the arthritis thing; after my 2003 broken (right) leg (and partially torn off foot), I developed arthritis in my right hand as well. The arthritis in my hand continued to get worse and worse, and by last year I was getting worried that it was going to impact me professionally as I make my living via computer. As I ramped my weekly and monthly mileage up to unprecedented (for me) levels, my hand arthritis seemed to reverse itself; I first started noticing better and less painful hand movement last September (my third consecutive 200+ mile running month). Initially I thought it was my imagination and/or wishful thinking, but now, nearly a year and over 2,100 miles in the log since April, my hand is so pain free I cannot feel any arthritis pain no matter how I move it.
Has my running "cured" the arthritis in my hand? I doubt it. If I quit running (for whatever reason) again, will the arthritis in my hand return? I'm thinking the likelihood is pretty high.