What Causes Severe Pain In Knee Along With Fatigue And Sweating?

Playing with my big dog outside and he ran straight into my leg almost bending it backwards, he made me fall to my knees I had gotten up and had an great pain and it just made me feel weird, so I went inside and sat on the couch, and instead of tunnel vision it was just getting darker and darker until I fainted then I woke up, and was very sweaty and very tired. How did this happen?