I Went Out For A Run On Friday, 29th Of

I went out for a run on Friday, 29th of January and as I was crossing the road my right leg sort of gave way and I hit the floor with a lot of force solely on my right knee, hitting it almost exactly on the kneecap. I've kept it rested however I have tried walking around/going up and downstairs etc, but I just can't do it. My knee has become so swollen you can no longer see my knee cap- it is extremely sore to touch above the knee cap, it's red hot, swollen and extremely painful. When I initially fell over, for about 2-3 hours afterwards I couldn't really feel my lower leg on my right side, that hasn't happened since however I can't put any weight on my leg now without extreme pain and I can't actually straighten it. Any help/advice for this?