In honor of being seven weeks post-op I went on a 25 mile bike ride last Sunday
Uh Oh! You have done too much, too soon. I did not get on a bike--- a real bike---until the weather broke in April---I had my BTKR in November of the preceding year.
It is difficult to compare the sets done in a weight-training exercise to that of cycling---but think of how many revolutions that your knees made over that 25-mile ride. You have. most likely, used your quads, hamstrings and the surrounding soft tissue way too much---and that soft tissue, at this stage, is easily inflamed.
I would ice, elevate, and rest excessively.
Think about it---25 miles is probably close to two hours of riding time, and think of the fact that you were not able to maintain the constant pressure on the pedals as you can on an exercise bike---you probably pushed really hard in spots.
After things settle down, I would stick to the exercise bike unit at least October---give yourself at least 12 weeks to relax---perhaps sixteen weeks would be better. Then, go gently for six-eight miles at an easy pace without hills or inclines---see how that feels, and then increase things ever so slightly each time.
It is better to take things a little too slowly than to go too fast.
Do not worry, though---I just finished getting 120 miles in this week. Down the road, a 25-mile ride will be a piece of cake.
I may have to re-think my plans to ride into Chicago from the Northshore suburbs on Friday to watch them practice for the weekend air show.
I would can that idea at this time---remember, riding a real bike and accelerating and handling even the slightest inclines is way more different than riding an exercise bicycle.