WishYou
If I were you, I'd start gently-gently and supplement outdoor running with plenty of cross-training.
If you can access it/ afford it, there is a new exercise trend at the moment called aquajogging - my local pool does it for about £4 a pop for an hour. It's quite fun! You get attached to a floaty water belt thing and 'run' in the pool - quite challenging, social, instructor-led, and maybe a good intro to running.
Also, if you are a gym member, use the cross-trainer - mimics a running motion and non-weight-bearing.
Maybe try a couple of activities like this a week with an outdoor run added, then gradually build up the proportion of running as your joints learn to bear weight.
IME it is not just that more weight = hurty joints. Your joints get 'built up' through exercise like anything else, I think. So I am not a skinny minnie, but I have been running since teen years, and never have joint pain (currently 30s). I imagine if you just started out of the blue and were overweight you might, hence I'd recommend the x-training to start you off.
Good luck, I hope you do start :)