Tkr 3 months ago and formed severe scar tissue. range of motion 87 @ 8 weeks. manipulation did not work. now 100 @ 13 weeks with spa therapy. should i have scar tissue removed now?

No: If you have progressed from 87 to 100 degrees of rom, you are doing well! this is something that you are going to have to continue to work at and gain flexibility with over a period of months. Be patient, yet vigilant with your exercises. Any consideration of scar tissue removal may occur at 1 year, but probably not even at that time. Continue to do what you're doing, because it's working.

Keep with it: 100 degrees is ok. It is more important to have full extension. Whatever you had pre-surgery for flexion is often what you have post surgery +10-15 degrees. So if you had 100 degrees of flexion prior to surgery don't expect more than 110 or so. Don't get more surgery if you don't have to.