What Causes Swelling In Ankles?

My legs ankels are extremely swollen (cant get into my shoes) stinging and burning sensation also. Finding it difficult to climb up stairs and kerbs. What could be causing same. Have it for approx 5 weeks now. Had same in one foot and leg up to the knee for about 4 months at the beginning of last year. Got blood tests and all came back clear re. kidneys and liver