What Causes Sharp Stabbing Pain While Bending The Knee?

I fell at work today dr just said nothing is broken patellar tendon looks swollen I cam down on my knee full force with my 350# frame on my left knee I can barely walk swelling has set in I have it iced im in pain but symptoms for the the patellar I have found says u cant straighten ur knee without pain I cant bend my knee without pain it being straight out it just throbs bending is sharp stabbing pain