RICE is the key to life right now. Without any other information I don't have much advice for you. Did you land directly on your knee/knee cap area?
Is there a lot of bruising? If there is you really should have an X-ray.
How long did it take for the swelling to show up? If it became swollen in less than a couple of hours....X-ray.
Are you having trouble weight bearing? If so...X-ray.
I'm sensing a recurrent theme here.
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS