If you can't sing, hum!

Bad news, y'all. I've got an injury...and the only cure..is more cowbell.
Ha, ha, ha! I wish! It appears (according to mister WebMD) that the symptoms are from a previous injury I sustained while playing Volleyball a few years back.
Patella Formalla or, "My-knee-cap-wants-to-get-off-its-rocker". It usually involves the loosening of muscles and ligaments.
I can still jog, run, dance, and do squats I just have a little bit of an uncomfortable feeling while doing it.
But, since I have to strenthen it up by means of special exercises distributed by my physician, it makes it hard to get in my cardio. Which was what my jogging and running was for.
I know what you're thinking, you're probably thinking that I'm gonna be on bed rest for like, 6 weeks again. Nope! I'll be doing yoga, pilates, and an ab workout series while I wait for my knee to recooperate.
*applause* Thank you, thank you! but, that's not all! *ooo!* How will I make up for lost cardio? swimming. Yes, Michael Phelps'n it up in my backyard. *hooray!* It seems like an obvious answer but, I racked my brain trying to figure out something for cardio while being nice to my knees. And that's why I think I deserve the next Nobel Peace Prize.
So, if I can't sing I'll hum. If I can't eat, I'll drink. And if I can't run, you bet your tube socks I'm gonna swim.
Thank you, and goodnight.

Sarah