I'm really not that old. About 6 years I really fucked up my knee. Split my patella in half and the break extended down to the tibia. Ever since then I haven't really been able to run, but for some reason I was able to jump rope without getting shooting pains. These days it hasn't been working as well. Even with knee supports and ice i'm hurting the next day. Anyone have any better ideas? Anything besides bike riding, which I find to be boring because of the amount of time to get a good cardio workout.