Anatomy: The hip joint is a ball and socket joint consisting of the femoral head and acetabulum with a large degree of mobility. The outer edge of the acetabulum is the glenoid labrum, which surrounds the acetabular rim and interrupts below the acetabulum, between which it is filled by the transverse acetabular ligament to form a week. The acetabular glenoid labrum is a fibrocartilaginous tissue that is deeply attached to the acetabular rim bone and is widest at its attachment, becoming progressively narrower outward and triangular in cross-section. The outer surface of the glenoid labrum is adjacent to the joint capsule, and the inner surface is involved in forming the joint with the femoral head, and its presence causes the acetabulum to form a larger than hemispherical cup to accommodate the femoral head. The function of the acetabular glenoid labrum is similar to that of the scapular glenoid labrum of the shoulder joint in that both play a role in deepening the cup. However, the function of the acetabular labrum lip is more importantly similar to a seal that maintains negative pressure within the hip joint to increase the stability of the joint. In the absence or rupture of the glenoid labrum, intra-articular fluid is lost, hydrostatic pressure decreases, and lubrication and protection of cartilage are reduced. Mechanisms of acetabular impingement: Precisely, FAI is not a disease per se, but an abnormal mechanical effect, but it can lead to damage of the hip joint. Various bony abnormalities of the acetabulum and/or femur lead to repeated impingement of the hip joint during activity, resulting in damage to the soft tissues (glenoid labrum and/or cartilage) of the acetabular rim. Depending on the mechanism of impingement, there are two types, cam-type impingement and pincer-type impingement, and although these two types can occur separately, in most cases the two types of impingement are present together. Cam-type impingement: the femoral head or/and the craniocervical junction area changes in morphology, with bony augmentation, making the femoral head “non-spherical”. When the hip is flexed and internally rotated, especially in the flexed position, abnormal contact is created between the femoral head or/and the craniocervical junction area and the normal morphology of the acetabulum. This abnormal contact stress pushes the acetabular glenoid labrum in the direction of the joint capsule, and the migrating area of the glenoid labrum and articular cartilage junction is subjected to uneven abnormal loading, resulting in cartilage injury or glenoid labral tear in the anterosuperior weight-bearing area of the acetabulum, with the anterosuperior region being the most common site of cartilage and glenoid labral injury. Clamp-type impingement: In this case, the femoral head can be morphologically normal and the cause of impingement is abnormal acetabular coverage. A common cause is excessive coverage of the femoral head by the acetabulum, i.e., the acetabulum is too deep. Another common cause is a posterior tilt of the acetabulum, where the acetabulum faces posteriorly in the sagittal position. This causes impingement of the hip joint during motion. Repeated impingement induces degeneration of the glenoid labrum, and bony growth at the base of the glenoid labrum leads to ossification of the acetabular rim, which further deepens the acetabulum and increases the coverage, forming a vicious cycle.