I Have A Knee Or Ligament Injury. I Believe It

I have a knee or ligament injury. I believe it happened while exercising earlier this week. Started applying heat to the area. It seems to feel alittle better as I had the heating pad on for most of the day. When I removed the pad, I had red blotches on the area. The red blotches seem to be fading. I was concerned about blood clots being an underlying cause but wasn't sure. I have a history of p.e, but I was tested and was found that the root cause was not hereditary but rather triggered by my surgery.