Boy I'd hate to start training for Boston with an injury. The ones that accumulate are bad enough. You are probably correct in pinpointing the knot as something at least involved with the problem, but knots, especially ones large enough to be easily found, do not necessarily resolve after just any massage technique.

My take on foam rolling is that it can be helpful for maintenance and minor problems. Major trigger points need more targeted pressure. Rollers tend to spread the pressure out too far and aren't specific enough to the spot that needs attention. A scattershot approach to pressure-based therapies can actually cause trigger points.

We'll assume the knot is in the Vastus Lateralis quad muscle and/or the superficial IT Band, which is capable of some contortion as well. Since you have found it and worked on it, what manual techniques have you used other than the roller? Finding it with your fingers, and pressing hard enough to define it and produce pain, is what we call palpation, an exploratory technique. To isolate the knot and treat it specifically, you want to use an ischemic compression technique.

Every now and then I will see a foam rolling video that shows a pause on the knots that hurt. That's sort of the idea, but it's like trying to open a power gel with baseball gloves on. Find a place where you can sit comfortably with your leg extended, taking care not to contract the quads so they remain soft. Get you thumbs and fingers down there onto that knot, find and focus on the center with slow gradual pressure. Aim for a 7 on the 1-10 pain scale, and hold it for 10 seconds or so. Slowly release to let blood flow back in to the area, and repeat a few times. Perform this technique a few times a day, and expect the re-learning process to take weeks, especially if you are continuing to train.

Sometimes, I have found it more effective to bend the knee and curl my fingers under the muscle to reach it from the other side. Grab a hunk of that quad and squeeze it while pulling it away from the bone. You can easily feel the groove between the quad and the hamstring tendon underneath. This has been a very productive strategy for me when I've had flare-ups in the same area. You can even do this in your car at stop lights. A few hits of several seconds each per treatment is all it takes. I consider this to be maintenance too, but obviously, you can't do this with a roller.

Good luck with your training. Your mileage is probably low enough at this point to resolve the injury before continued training makes that a very difficult task, but many athletes do their speed and hill work at this time. I'd back off on any hard training until you can gauge some progress in this injury.