So.. I'm a pretty skinny guy. I'm about 181cm and weigh 47kg (and that's after putting on weight). A few years ago, I was going through a rough patch in life. I'd just gotten out of a long relationship (girlfriend of two years cheated on me), my mum was having breast cancer operations and I'd failed my diploma (SysAdmin). I kind of became some sort of NEET. I'd avoid leaving the house unless it was to go to my best friend's place. At once stage I didn't go outside for ten days. I'd go to sleep at 6AM, wake up mid-afternoon. All I did was chat on IRC and play TF2.
So, suffice to say, my body wasn't in the best of shape. Remember that episode of Seinfeld where shortly after Susan died, George lost the use of his legs because he sat around for so long? Yeah, that kiiiinda happened to me.
I was at my friend's place. He'd just gotten a 24" LCD monitor and Uncharted 1 had recently come out, so we were playing that and being blown away by how great it looked. I was sitting on a chair and went to stand up. Suddenly I had this amazing pain in my left knee and I could feel the blood drain out of my face (lol shock). I gently moved back down and realized I couldn't move my leg without causing horrendous pain. I felt like I was going to throw up. I tried to move myself over to the couch to lay down, which was about thirty centimeters away, but I couldn't do it.
My friend, bless him, went and got a packet of frozen peas to put on my knee while I called my mum and explained that I needed help. She had to finish up work, so it took her about an hour to get there. When she did, she and my friend's mum tried to pull the chair back into the hallway so they could have a proper look at my leg. Nope, I screamed and cried with pain. So, they called an ambulance.
When they came, they gave me one of those painkiller-meth-pen things that you inhale. Damn those things are good. They put me on a stretcher and into the back of the ambulance, where they diagnosed that I'd dislocated my kneecap. I don't remember much of what happened on the way to the hospital, but I do remember one of them remarking on how they didn't get paid much for what they did. I slurringly asked if they still felt it was worth doing, and they said "Absolutely". I knew I was in good hands.
So we get to the hospital and when I'm in triage, they pop my knee back in (with a gross cracking noise). The pain almost immediately subsides and after checking me over, they send me home.
That wasn't the last of it, though. A week later, I was laying in bed and rolled over. Guess what happened. Yup. Out comes the ambulance again, meth-pen in check. They pop my knee back in on the ride over, but they want to give it an X-ray. Turns out the muscle-tracks behind my kneecap had grown really weak due to under-use. I had to have physio-therapy, which involved a hot young Scottish chick rubbing my leg with sorbelene cream twice a week (I liked that part).
It's fine now, though I can't run or jump like I used to.