That sucks, Ben.

I remember reading in your blog about your knee problems, but for some reason I thought they had just worked themselves out. I know what you are feeling, and it's not a good feeling at all. I'd recommend taking up weightlifting, as it's a good way to get sweaty to music and push yourself. Sure, it's not nearly as empowering and individualistic as footbag, but it's as close as I have found that doesn't put a lot of stress on the knees (biking too, I guess).
My knees felt fine today, as least for walking and jumping, but I'm still unsure about blind landings. I'm not sure how easily understood this idea is-- but I've noticed that it's not jumping up and down that makes footbag so hard on the legs, it's that we almost always land without focusing on landing. By not anticipating the landing, we can't make it as streamline, and as a result more stress is generated and more shock absorption necessary. So while I can jump up and down and feel fine, I can't say that my knee would be able to handle blind landings well. I'm gonna wait till at least saturday, and even then I might just do pixie sets with no downtime component to be safe.
Brian and I went to the YMCA today and lifted weights for about an hour. He went upstairs and used the weightlifting equipment (machines, contraptions, etc.) while I just did freeweight stuff. It was fun, but I'm sure no pro. I fixed a dumbell to begin with and, upon picking it up, the weights on one side fell off (cause I didn't remember to fasten a clamp on the end).

Humility is a good thing, I guess.
After the weightlifting we played in the pool for about two hours, seeing how many headers we could be back and forth between us, then eventually evolving into a game where we would throw passes between us and try to head the ball into the lifeguards. The two lifeguards were really enjoying it and we even got these two young (5 to 8 year old??)kids to play too, which their parents were happy about. Overall, it was fun feeling like a kid and just making people happy.
I wanted to swim today since it's a good light-impact way to work the legs, and doing headers actually meant that we did a lot of blind landings. At one point my knee felt a bit tweaked, but that was for a short time and it's felt fine ever since.
Sorry this entry is long and doesn't even have an interesting oddity about it. I was gonna insert a 'g' as the second letter to every word, but since it's such a long entry, that's just too much work.