New Shoes – bad knee

Patient: HelloThank you for taking my question.I’ve been runinng for about a year, did two halfs and then the Detroit Marathon.I bought a new pair of shoes on Dec 30 and have run about 70 miles in them so far. But now I have pain in my left knee, gets worse when I walk down stairs and after I’ve been sitting for a while. Sounds like Runners Knee. I tried runing this morning but only made it down the block before the pain so so bad I had to walk home.I’ve run a few more miles than I normally do, 30 mpw instead of 25. But I’m convinced it’s the new shoes that hurt my knee.What can I do to get back to running? Exercises? Motrin? How long should I wait?Thank you