exercises for bad knees

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So, last week I was diagnosed with Patellofemoral Pain Syndrome. Basically it means that my knee caps don't line up right with my knees and when I bend my knees they can rub bone on bone and cause pretty bad pain. I was wondering if anyone knew of any exercises I could do. The dr gav me some knee/leg strengthening exercises, but that can take weeks or longer for it to correct my problem. Right now I'm basically walking, but I need to ramp it up. I enjoy jogging, but hey I'm a big girl and jogging hurts my back after a little bit, so I do it in 30 second/1 minute increments. The dr said the only way to really fix it is to lose weight, but how can I do that when everytime I do more than walking, I throw my knees out!?! Ugh! Ideas, please?