Iliotibial (IT) band syndrome is appropriately also known as runner's knee. Although runners aren't exclusively affected, they are by far the most susceptible group.
If you have IT band syndrome, you will probably feel a stabbing pain or burning sensation on the outside of your knee during physical activity. This won't usually occur at the beginning of physical activity, but rather in the middle.
You have two IT bands, one stretching across the outer side of each leg. Each begins about half way up the outside of the thigh, almost as high as the hip, runs down over the outside of the knee and attaches at the top of the tibia (shinbone). As you bend and straighten your leg, the IT band slides over a bony bump on the outer portion of the knee called the lateral femoral epicondyle.
As you frequently bend and straighten your knee during physical activity, your IT band slides up and down more often over the lateral femoral epicondyle, similar to how a mountain climber's rope slides over rocks as he or she moves left or right. This causes lots of friction on the IT band, similar to the friction on the climber's rope. Over time, the friction can cause inflammation of the IT band and the pain associated with IT band syndrome.
That's why runners, particularly those who cover more than 12 miles (19 kilometers) a week for several months in a row, commonly experience the condition. Besides distance, running downhill is another contributing factor as it increases pressure on the knees. People who have poor foot mechanics while running are also at a greater risk of IT band syndrome, as conditions like over-pronation (excessive inward rolling of the foot) place more stress on the knees.
Not all runners will develop the condition, however, and some people who never run might. Activities that involve rigorous knee movements, like cycling and ballet, as well as a dramatic increase in physical activity can also cause the condition. Studies show that a number of other variables, including improper footwear, structural or functional problems in the legs and feet and duration of activity are also a factor.
If you have IT band syndrome, your healthcare practitioner can help reduce your pain and inflammation. He or she can also use a number of tools and techniques to help you return to activity and can recommend steps to help you prevent the condition from returning. One of those recommendations might be to reduce participation in knee-intensive activities, and until the condition heals you should probably avoid such activities entirely.