So...
I'm hoping it's just a pulled/strained muscle or ligament. I woke up at 4 am this morning because I heard the cat throwing up and I always try to get something to catch it or at least direct her to do it onto a surface like the kitchen floor (vinyl vs. carpet). So, I swung my legs out of bed and that's all she wrote. To the left of my left knee (not by the knee cap- toward the rear) something popped. It wasn't audible but I felt it. At first I thought it was no different than when my knees pop in general- sometimes my knee will pop if I twist or turn to one side. But that's not the case.