As a distance runner, and coach in a marathon training program, one of the most common injuries I've seen is ITBand Syndrome. Even veteran marathoners can fall to this.
What is ITBS?
In a nutshell, the illiotibial band is the long tendon-like connective tissue that runs from just below the hip to the knee. Runners sometimes refer to their injury as "runner's knee" because that's where they may be feeling the most concentrated pain. Others may complain about hip pain. Either way, it can be very painful, bring an abrupt end to a runner's event, or force a change in how you tackle your training.
A friend of mine, a highly experienced and well-known local African elite runner, was brought down in the midst of his Olympic trial last year by an ITBand injury. Another friend, a non-elite veteran with more than 50 marathons under his belt, was forced to walk through the majority of our training season last year because he injured his ITBand by accidentally turning his knee the wrong way. I've been battling ITBS ever since I got injured when wearing the wrong model shoes. Bottom line: it can happen to anyone.
More often than not, I've seen it in situations of over-training, over-striding or running on cambered (sloped) surfaces. There are any number of factors that can contribute to the injury and symptoms can vary from one person to the next. In my case, I felt acute pain in the side of my hip below the joint and behind my knee, and I was wobbling significantly at the end of a relatively short run (6 miles). Although, in comparison to my friends mentioned earlier, I'm nowhere near as advanced a marathoner, I am experienced enough to know when to back off in intensity, stride or distance and to not try to run through the pain.
Your doctor and probably a sports therapist, should be consulted at the outset of symptoms. It also seems that, once injured, you can be prone to future injury, I think because you're probably continuing to train or participate in events.
As a coach, my first suggestions to trainees is to back off running, get treatment immediately, and learn to walk. I can't tell you how frustrating it is for a runner to have to walk - it can actually hurt because the muscles must work differently and longer! Then you have to learn how to stretch the muscles for greater flexibility, as flexibility is key to running injury-free. One of my coaches, a former Olympian, suggested I take several doses of vitamin C to help speed the healing process.
I have a hip rotation and leg length difference cause by mild scoliosis that contribute to my being prone to ITBS. However, my wonderful team of health professionals keep me running down the road. There is a lot to know about ITBand Syndrome, but mostly that it doesn't have to completely keep you from ever running again, if treated promptly and properly.
Running Injuries, Jeff Galloway
Iliotibial Band Syndrome: A Common Source of Knee Pain, American Academy of Family Physicians (AAFP)