I'm going to have the >90 degree restriction for 6 weeks (posterior approach), but I'm thinking I can ride a stationary bike without breaking that as long as the seat is adjusted the correct height and I get on the easiest side. I'm planning ahead because my surgery will be in the dead of winter in upstate NY and I need to do something inside to get some good aerobic exercise in addition to the leg and hip exercises the PT will have me doing. Are any of you riding a stationary bike? If so, how soon after surgery did you start and how did it go? Is your surgeon and PT OK with your doing this exercise? I will definitely clear it through my surgeon and PT before I start, but I want to purchase it before I have the surgery and want to get some info from those who are using this as a form of exercise afterwards. I'm thinking of a recumbent bike because I have back problems too.