The Iliotibial (IT) Band is a long, thick band of connective tissue that extends the length of the thigh, providing a mechanical link between the powerful muscles of the hip and the bones of the lower leg. Understanding where this structure originates and terminates provides insight into its function in walking, running, and maintaining the alignment of the hip and knee joints.
Defining the Iliotibial Tract
The Iliotibial Tract, commonly known as the IT Band, is a dense, longitudinal fibrous reinforcement of the fascia lata, which is the deep connective tissue sheath encasing the muscles of the thigh. It is not a muscle; rather, it is a non-contractile sheet of collagen fibers. This tough structure runs along the entire outer (lateral) side of the thigh, functioning primarily to transmit forces and stabilize the knee.
The tract begins high up at the side of the pelvis and continues uninterrupted past the hip joint, down the thigh, and across the knee joint. It acts as a dynamic brace, helping to control the movements of the thigh and lower leg during activity. Tension within the IT Band is controlled entirely by the muscles that anchor into it at the hip.
Anchors at the Hip and Pelvis
The proximal, or upper, attachments of the IT Band are located near the hip and pelvis, where the fibrous tract receives contributions from two major muscle groups. The Tensor Fasciae Latae (TFL) muscle is the primary contributor, blending its tendinous fibers directly into the anterior (front) portion of the IT Band. The TFL originates from the iliac crest, near the anterior superior iliac spine.
The second anchor comes from the Gluteus Maximus. A large portion of the upper and superficial fibers of the Gluteus Maximus insert into the posterior (back) aspect of the IT Band. These muscle contributions make the IT Band the shared insertion point for both the TFL and a segment of the Gluteus Maximus.
The blending of these muscle fibers into the tract occurs near the greater trochanter, the bony prominence felt at the side of the hip. When the TFL and Gluteus Maximus contract, they create tension throughout the entire length of the IT Band. This tension allows the tract to perform its functions of hip abduction, hip rotation, and lower limb stabilization.
Insertion Point at the Knee
The IT Band continues its path down the lateral thigh until it reaches its distal insertion just below the knee joint. The main insertion point is a bony prominence on the shin bone called Gerdy’s tubercle. This tubercle is located on the anterolateral surface of the lateral condyle of the tibia.
This specific attachment site connects the powerful hip muscles, via the IT Band, to the lower leg. The IT Band also has secondary attachments, including fibrous slips that anchor to the lateral femoral epicondyle, the bump on the outer side of the thigh bone just above the knee. These secondary slips help stabilize the knee against side-to-side forces.
The connection at Gerdy’s tubercle enables the IT Band to stabilize the knee, particularly when the leg is straight or slightly bent. As the knee flexes and extends, the tension in the IT Band shifts, providing dynamic support and controlling the movement of the tibia relative to the femur.