Iliotibial Band Syndrome
The ilio tibial band runs from the hip to the lateral side of the proximal end of the tibia. It's function is to resist internal rotation of the tibia as well as to maintain the lateral integrity of the leg. Ilio tibial band "friction syndrome" is a condition wherein the ilio tibial band is stretched and torqued and the distal end rubs across the lateral condyle of the femur.

Patients complain of pain on the lateral side of the knee often extending up the lateral side of the thigh as high as the hip.

Over stress of the ilio tibial band. During a normal gait cycle, the femur and the tibia rotate in unison (i.e. internally during pronation and externally during supination). However, when a person over-pronates, the tibia is locked into the Talus by the saddle joint and therefore continues to rotate internally past the end of the contact phase while the femur receives its orders from the brain and begins to rotate externally at the beginning of midstance. The resulting counter rotation of the femur and the tibia causes a shearing force to occur in the ilio tibial band which becomes torqued and stretched. The result is that the distal end of the band rubs across the lateral condyle of the femur.  Other conditions that can contribute to this syndrome are genu valgum and leg length discrepancies.

Since the primary cause of the condition is overpronation of the subtalar joint, a custom orthotic works well in treating the condition.