I am 49 year old male, 6 feet and 200 pounds. While playing football, I ran out for a pass, planted my right foot, went to cut and I heard and felt a loud pop and I went to the ground. My leg is swollen from my knee down to my ankle. I have bruising behind my knee and on the inside below my ankle. This happened seven days ago. I can walk, but my leg is stiff and sore. What is wrong?