Can someone come up with any reason for my severe knee pain?

It could be a number of things, including a torn ligament or a cartilage issue. Sometimes localized steroid injections will help, they did with my mom, who has been a chronic knee pain sufferer for years. Steroids completely took her pain away for months, but they can damage cartilage. It may require surgery, as it did with my mom and ex boyfriend. I would see a doctor for an x ray or MRI and proceed from there.