My Doctor Says I Have Osteoporosis Of My Left Hip.

my doctor says I have osteoporosis of my left hip. At present I am not experiencing pain there. For almost two years I have had left knee pain. This past week I can hardly swat without pain, and then when I stand from a swatting position, the pain is unbearable, When I get up from a sitting position, it is painful. My xray shows normal (how can that be) will an MRI show anything else. I had a bone density test, it shows moderate osteoporosis