What Storm and Bla said.
2 years ago I was dirt biking with friends, and I was riding a 250 and was at the top of 4th gear. So I was goiing about 45 miles per hour. Came around a corner and saw 2 dumbasses from another group just parked in the middle of the path.
I saw them and saw that I had maybe 60 feet to stop. So I killed the engine, hit the back brake, tried to stop. Noticed I was still going to fast so I had to slam on the front brake. So I was probably going 30 to 35 MPH at this point. Whoel bike fishtailed, launching me over the front handle bars. I flew a good 6 or 8 feet through the air and the first thing I landed on was my knee. Bounced several feet then proceeded to slide face down in the dirt 15 feet along the ground and came to a rest between both of em who just sat there on their bikes staring at me.
Not one of them bothered to help me out at all. So I was on the ground the whole time unable to move from the pain shooting through my whole body. I had to wait another 15 seconds or so for the guy in our group who was behind me to catch up and help me up.
My knee was killing me and was in severe pain. But i still rode 3 1/2 more hours thinking the pain would go away. Later that night, my friend accidentally slammed his knee into mine, causing my knee to fill up with liquid and swell up to litterally 4 times its size.
For 3 weeks I couldn't walk without limping. And now 2 years later I can't run more then a short distance without a sharp stinging pain filling my knee. I also can't stand on it for long periods of time, or walk long distances.
So get that shit checked out man, you don't want it to screw you over for the next few years.