Iliotibial Band Syndrome (ITBS) is a common overuse injury among runners, characterized by pain on the lateral aspect of the knee due to irritation of the iliotibial band as it moves over the lateral femoral condyle during repetitive knee motion. Its etiology is multifactorial, involving both extrinsic factors (training load, surface, footwear) and intrinsic factors (muscle weakness, poor flexibility, altered biomechanics, and impaired neuromuscular control). The incidence of ITBS ranges from 5%–14%, with a higher prevalence in men. Two main anatomical theories explain its cause: the compression/enthesopathy and friction/impingement theories.The ITB functions dynamically, acting as a knee extensor below 30° of flexion and a flexor beyond that point, with peak impingement occurring around 30° of knee flexion. Biomechanical abnormalities such as excessive hip adduction, pelvic drop, weak hip abductors and external rotators, and poor core stability increase tension on the ITB and contribute to pain and dysfunction. Recreational runners—who constitute a major group affected—often demonstrate altered lower-limb kinematics, including reduced rearfoot eversion, tibial rotation, and hip adduction angles.Weakness of the lateral gluteal and core muscles may lead to excessive pelvic and trunk motion, further increasing ITB strain. Stretching alone does not effectively modify ITB properties; instead, attention to proximal biomechanics and neuromuscular control is crucial for prevention and rehabilitation.