What Causes Complex Regional Pain Syndrome In Knee?

I Have complex regional pain syndrome in my right knee, I fell over because of my knee and tore my calf muscle in my left leg, its been five weeks and still painfull as ever and very sensitive to touch. I had my first physio this week and hes said that he thinks ive now got CRPS in my calf now as I shouldnt be suffering with this much pain, not convinced and not sure what to do, could you give me some advice?