Knee pain staying

Question
I am 26 and I have been running for ten years, about 25-30 miles per week.  Recently, I injured my back and haven't run for the last five months.  I did continue walking.  For the last month, I've begin to run, about half my speed and only for twenty minutes, not even two miles.  When I wore heels one day, I realized that when I overextended my knee, it hurt really bad.  I thought nothing more of it.  However, a couple days later when I was running, I felt a sharp pain in my right knee while running, causing me to stop.   Since then, I've had aching after running, about 1 inch below my kneecap, right below the center.  I've laid off running AGAIN but have continued walking.  However, now the pain is constant and gets worse even walking.  So what do I do to help and what exercise CAN I do that will be safe while I rest off this knee?  Ps:  In the past, this right knee has caused me problems, but I've ignored it!!  
Hope to hear from you soon
andrea

Answer
Andrea,

You should see a doctor. It sounds very much as if your patella has slipped out of the groove it normally operates in. This causes it to rub wrongly and leads to pain. It isn't super serious; however, it needs to be corrected. You will also most likely be put on some leg exercises to strengthen one side of your leg. This usually happens because certain muscles are stronger than the others around the knee and tend to pull your patella out of place. Hope this helps. See the doctor!!

Ryan