Symptoms
This mouthful causes a pain on the outside of the knee when the lower end of a sheet of gristle running from the thigh rubs over the bony prominence on the side of the knee. It only hurts when the knee is moving through a particular angle, and it is more common when running downhill.

Signs
Pressing on the tender area and moving the knee should be enough to convince you, but your doctor will want to see your running action and to check whether you are bow-legged or supinate. If you have pain on one side only it may be because you always run on a camber or have legs of different lengths!

Medical investigations
Unless the doctor thinks that there is internal damage, he will probably just check your gait and shoes. A scan can confirm the diagnosis.

What else could it be?
A pain in the outer side of the knee can also be due to a strain of the lateral collateral ligament, which hinges the knee joint, or a trapped synovium (knee lining).

Self-treatment
Ice it, ice it, then ice it some more. Also, check that you are not wearing old shoes, and try running on the other side of the road if the pain is one-sided. Lower your mileage.

Medical treatment
If your footwear or gait is causing ITBS, you may need orthoses or build-ups to the outer side of your shoe. Exercises which stretch the band can help, while ultrasound or a cortisone injection should cure the problem. Although massage is often recommended, it sometimes makes the inflammation worse.

Can you run through it?/Recovery time
Improving your biomechanics can make a dramatic difference, and you could be running properly again after a week. Ignoring the pain will probably make it worse, unless you switch to better shoes or training terrain!