Went to ER for knee injury found out it was ligaments but for the last two day my leg and ankle has been beyond swollen what's causing that?

Gravity. Knee injuries can cause swelling in the lower leg, ankle, and foot. The swelling travels down with gravity. However, you should be checked asap to make sure that you dont have a more serious problem such as a blood clot.
Get it checked. Sounds like you need to have your leg and ankle checked out. If you have a pcp go see them or return to the er.