Thanks for your reply. I was in good shape pre-surgery and I am a long distance biker so the rides seemed comfortable.My knees still feel a little strange in water so biking is the low impact exercise of choice. I might have torqued my knee doing exercise or even a rapid movement on the bike. Ironically, biking feels better than walking to me. The X-rays didn't show any damage to the appliance- yeah- but not knowing what it is bothers me. Let's just hope it goes away. I just landed at my vacation destination with my bicycle, so we'll see how I do this week! Thank you!