Your original injury sounds like something I had when I had been cycling about a year. I was climbing a short hill when my DS was coming down. He was on his cross bike, with no water, so I passed him my bottle, for a sip. But, I dropped it when he gave it back to me and I crashed. No visible injuries, but a week later I had a huge hematoma on my knee. I could barely walk, so I went to the doctor, then to an orthopedic surgeon, who was sure I needed surgery! One MRI later, it showed a huge amount of blood in the hematoma. I went back to the ortho, he drained it, and I was better within seconds. I am betting this *is* related to the original injury and perhaps you need that checked out.