My knee didn't hurt as bad as yours but it did used to hurt on every run, particularly when hills were involved. I cured it completely by changing my running form and switching to minimalist shoes. If nothing else has worked its worth a try as a long term solution.

OUCH! I can relate! First of all congrats on your training thus far and on making the decision to pursue your 2nd marathon. I have to ask, is the injury from running? Or something else? You said you are taking Naproxen - was that prescribed from your doc, or are you taking some generic OTC stuff? If you did see a doc, was he/she an orthopedic doc or just a general practitioner? What did he/she say?

If you didn't see a doc, go and see one, preferably an ortho, that runs as well. See what he/she says. 4 weeks out might be enough time to rest it, depending on what you have. Get an MRI and/or xray done to make sure nothing is broken or torn. If nothing is broken/torn, and it's something like ITBS, runner's knee, etc. it may be a case of overtraining or too much too soon, especially since you say you aren't a high mileage runner. You may be able to R.I.C.E. it (rest, ice, compress it, elevate it) in the meantime, lay low on the running, and keep your fitness up by doing stuff like biking or the elliptical til then.

But I KNOW how you feel! I have run many marathons and had to DNF for the first time in late 2010 due to a nasty injury. I, like you, put in a ton of time and training, only to get a nasty case of ITBS 2 weeks before the race. I saw a doc, who was also a runner, and he told me I may be able to run it but suffer the consequences later. (In hindsight, it was bad advice). But I tried to rest it, etc. and come race day, it hurt so bad by mile 3. I had NEVER given up on a marathon but I had to that day. I swallowed my pride, limped over to my friends at mile 13, and dropped out. :-( I couldn't run for 3 months after that, went to physical therapy, and tried to focus on other forms of exercise.

For me, it wasn't worth it injuring it more. There always will be and was other races. In fact, I returned to that same race the following year, healthy and strong, and PR'd! I am a stronger runner now, and have changed the way I train, upped my mileage slowly, and took care. It made me a better runner.

So see your doc and see how you feel. You may have to rethink any time goals you have if you do decide to do it. I'm telling you, I love to run, and it sucked that I couldn't run for 3 whole months after that.

Good luck to you, I feel your pain!

But I really just want to be someone who is still running at age 70...and not necessarily has a couple dozen marathon medals.

I think you should definitely sit out the race as to not further injure yourself. But if you want to keep running, you should start off taking it easy while your knee heals and do other types of cardio. Then I highly recommend reassessing your running form and trying to make changes to improve it. For some reason, doctors and other experts tend to focus on fitting the runner to a pair of shoes that fits their poor running form, instead of having them improve their running form so they can wear a variety of different shoes. For instance, modern trainers typically have very thick soles that promote heal-striking, but this is bad for you because it can cause foot injuries, shin splits, knee injuries, lower back pain, and more. And most of us do run incorrectly if we put on modern running shoes without developing proper running form. You are better off buying shoes that are more like racing flats or even minimalist. But if you decide to go this route, start from scratch with low training volume to give yourself time to adjust to new running form and/or new footwear.

Or you can continue status quo where you have knee problems and your doctor will probably tell you that you aren't cut out for running and should find another hobby. I know one person who was told this, and never once was her running form even talked about.

http://www.dailymail.co.uk/home/moslive/article-1170253/The-painful-truth-trainers-Are-expensive-running-shoes-waste-money.html

Have you tried any accupuncture for the pain? It can help. II have also discovered that icing an injury the night before my morning run and taking an ibuprofen before bed seems to make more of a difference than icing it immediately after a run. Maybe just because I have more time to spend on it, I don't know. But it makes a big difference for me.