Im only 20 n my knee is constantly killing me..?

Evey time I bend down I get this horrible pain in my left knee..I can't even really run anymore.this pain is getting intense..on that same leg I have a bone bulging outta my ankle..from a axident wen I was a kid..the emergency room back then did nothing but tell me it waz a real bad sprain n sent me home with cructchs..now a coup years later I got a bone stickin out n it kills me..could this also have sumthin to do with my knee? Everytime I bend my knee I hear my bones clickin..kt hurts so bad.I dnt have a doctor to go to..n I'm scared..I need my legs.n don't kno wat id do without it..I walk everywhere cuz I have to..my roomate is scarin me tellin me my kneecap could be cracked..what could this be? As long as I dnt lean on it while walkin I tend to be ok..but it still clicks 247..n as soon as I lean on it the pain gets really bad...as a kid I jumped fences,ran from cops,waz in track,n I use to sneak out the house from jumpin off my roof.its like a seven foot drop n id land straight on my feet feelin pain run up through my legs.I kno this is probally kharma hitting me back...but seriously wat could this be? N has nebody ever had this problem be4?