A most unusual ankle/leg injury?

I was crouching in a catcher's stance for 10-15 mins. while I made a home repair on my roof. My feet and lower legs fell asleep during the time I was up there. After I was back on the ground and feeling returned to my limbs, I felt MAJOR pain and noticed a quarter-sized knot that felt very hard to the touch. It is on the spot where my lower leg meets my foot. After about ten mins., the area turned a light purple color, like a bruise. I did not strike the area against anything, so I feared a blood clot (I have a history of DVTs). So, I went to the ER and the doctor very rudely (after not even examining my foot/ankle) stated it couldn't be a blood clot because "blood clots don't happen there." That was twenty four hours ago, I cannot bear weight on it, nor can I extend it. If it isn't a circulatory issue, what else could it be?