Due to a recent injury and surgery* (see story below) I've been told that I should not be a runner or a singles tennis player in the future. I am wanting to get an exercise bike to help with my physical therapy but also to use after that. Can anyone explain the advantages and disadvantages of a recumbent versus an upright exercise bike? Which is the recommended type for knee physical therapy? Are there any specific models you can recommend? Or would an elliptical machine be a better choice? Thanks for any and all help you can give. TripleB * I'll try to make a long story not so long: Injured myself playing tennis, family doc thought it was a sprained ligament, week later went to orthopaedic doc, took MRI, turned out to be cartilage damage. Had Microfracture Surgery Monday, alot more damage in there than doc thought, pulled out 6 large pieces of cartilage, repaired a good bit more damaged cartilage in several places, made 7 holes in my bone (I watched the video and counted...ugh) to create a 'good' blood clot to hopefully form new cartilage. Can't put any weight on the leg for at least 6 weeks, on a CPM machine now, and physical therapy will begin in January. Doc said that I couldn't be a runner or a singles tennis player any longer. If I tried then I would be back in his office in 6 months having knee replacement surgery. If the procedure worked, physical therapy went well, and a future MRI showed positive results, I should be able to play doubles again 8 to 15 months down the road.