What Causes Blood Clot In Leg And Elbow?

Am Claudette Robichaud FRom Canana NB, I had a bood cloth on my left leg before,then left my leg and went to the inside of my right elbow..can you tell me please, how do I get those blood cloth from. my e-mail YYYY@YYYY .. and how do I tell if another blood cloth should appeared again..thank you soo much.