I will tell you the only way I know to repair these jeans. You will have to take out a portion of the outseam so you can get the jeans on your machine. using your mending stitch, stitch over the worn spot. What I prefer to do is put my darning foot on and using a matching thread, straight stitch with the twill pattern of the jeans going over the worn spot trying to make it look as much like the original thread as possible. Both ways will be noticable, but the last is less than the first. Good luck!