Q: I have pain in my knee. My doctor thinks it might be ITB syndrome. What is it? Is it treatable?

A: "ITB syndrome" is short for iliotibial band syndrome. It refers to a common cause of knee pain.

The iliotibial band is a tough fibrous (scar-like) tissue that extends from the region of the hip to the knee along the outside of the leg. Along with other muscles of the leg, the IT band helps stabilize the knee, especially when the knee is stressed during physical activity.

ITB syndrome develops when there is damage, irritation or inflammation of the IT band. The most common site is at the outside of the knee where the tissue of the IT band rubs over a bony bump.

Pain over the outside of the knee is the most common symptom, although some people complain of pain higher up, along the outside of the thigh or hip. Repetitive knee flexing tends to make it worse. Rest usually relieves the symptoms.

While ITB syndrome may occur for no apparent reason, it's common among people who are:

--young or middle-age athletes, particularly if not very flexible

--engaging in activities that require repetitive flexing and extending of the knee (especially running)

--increasing their exercise intensity (such as upping the miles they run)

--bow-legged, have flat feet, or have legs of unequal length

Treatment options include:

--adjusting one's exercise routine

-- physical therapy that includes stretching and strengthening exercises

--applying ice to the area where you feel the strongest pain

--improving footwear (including using shoe inserts for flat feet)

--anti-inflammatory medications (such as ibuprofen or naproxen)

In cases where these measures don't work, doctors may recommend a cortisone injection or even surgery to remove a bony bump that's irritating the IT band.

(Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center, Boston, Mass., and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. )

(For additional consumer health information, please visit www.health.harvard.edu.)