I twisted my left knee last week while doing construction work. It is still tender on the inside bone and has some arthritis, but not much more than a bother. The more serious thing that showed up shortly after the twist was swelling from just below the knee down to and including the ankle. I had an x-ray (thus the arthritis diagnosis) and an ultrasound, which ruled out a blood clot. There is pain when I walk - on the back of my calf for about six inches below the knee crease. It feels like a very tight tendon, and causes me to limp. There is no other pain. I have been working in a moldy basement, but haven t had any mold related symptoms. I also looked closely for a spider bite but found no marks. I m due for a blood test tomorrow. My doctor wants a MRI, which I can t afford in addition to the ultrasound. Any ideas as to what is causing the swelling of my left leg below the knee? P.S. My right leg is normal, and I feel healthy otherwise. Thank you, Art