The kneecap or patella rests in a indentation within the thigh bone (femur).  In a healthy individual the patella glides up and down in a straight line within the groove as the knee bends and straightens.  If an inbalance exists in the side to side forces pulling on the patella the patella gets pulled outwards as it glides upwards in the groove.  This leads to excessive friction on the cartilage on the inner surface of the knee and...

The iliotibial band (or ITB for short) is a wide band like tendon.  It originates at the hip, passes down the outside of the thigh and attaches at the upper outside of the shin bone (the tibia) just beyond the knee.  The Iliotibial band runs over the lateral femoral epicondyle which is a bony mound on the outer aspect of the knee, and it is susceptible to friction at this point.  At 20-30 degrees of knee flexion (bending) friction is at it...