Iliotibial Band (ITB) Syndrome Definition
Iliotibial band syndrome, or ITBS, is due to inflammation of the iliotibial band, a thick band of fibrous tissue that runs down the outside of the leg. The iliotibial band begins at the hip and extends to the outer side of the shin bone (tibia) just below the knee joint. The band functions in coordination with several of the thigh muscles to provide stability to the outside of the knee joint.
Iliotibial band syndrome describes the pain caused by inflammation of the band as it crosses the lateral condyle of the femur. When the leg is in a straight (known as extended) position, the band fibers are anterior to, or in front of, the condyle (a bony projection on the femur, or thigh bone). As the knee flexes, the fibers move across the condyle and are positioned behind or posterior to it. A bursa or sac in this area allows the iliotibial band to glide over the end of the femur.
When the band becomes irritated, friction may occur with walking or running, causing knee pain due to inflammation on the lateral part of the knee joint.
If symptoms are ignored, further inflammation and scarring may occur in the bursa, causing progressive pain with decreased activity.
Endurance athletes are especially prone to developing iliotibial band syndrome. Athletes who suddenly increase their level of activity, such as runners who increase their mileage, often develop iliotibial band syndrome.
Symptoms of Iliotibial Band (ITB) Syndrome
Knee pain is the primary symptom due to inflammation as the iliotibial band slides across the femoral condyle on the outside, or lateral, aspect of the knee. Pain is most severe with the heel strike of walking or running and may radiate from the knee up the leg to the hip. Pain may also be felt with knee flexing, especially going up or down steps.
As the bursitis grows worse, pain may radiate up the side of the thigh and down the side of the leg. Patients sometimes report a snapping or popping sensation on the outside of the knee.