Acetabular dysplasia is more common in young women. The majority of patients have no clinical symptoms during adolescence, but as they age, they gradually develop hip pain after walking, and acetabular dysplasia is detected incidentally by taking radiographs. If the CE angle was less than 20°, the acetabular dysplasia was determined. Depending on the degree of subluxation and the onset of pain, there are three age groups of acetabular dysplasia: severe subluxation with pain starting around 20 years of age, moderate subluxation with pain starting between 30 and 40 years of age, and mild subluxation with pain starting after 50 years of age. Acetabular dysplasia is the most common cause of secondary osteoarthritis of the hip joint. 25% to 50% of osteoarthritis of the hip joint in the age of 50 is caused by acetabular dysplasia. Acetabular dysplasia decreases the area of the acetabulum covering the femoral head and causes an imbalance in the acetabular accommodation, resulting in shear forces at the acetabular rim and increased stress in the stress area, which eventually leads to instability and anterolateral displacement of the femoral head. If shear forces persist, the soft tissue of the acetabular labrum loses compensation, the glenoid labrum and the round ligament degenerate, and the upper glenoid labrum tears. With secondary damage to the acetabular labrum, the stability of the hip joint and the lubrication mechanism of the articular cartilage are disrupted, the intra-articular pressure distribution and the confinement of the joint cavity are altered, and the load-bearing zone is overloaded beyond the capacity of the osteocytes and chondrocytes. In order to maintain the stability of the hip joint and to keep the femoral head in the hip joint, the upper lip of the acetabulum becomes hypertrophied and the glenoid labrum wears away due to the growth of bony redundancy. If the glenoid lip and the hyperplastic synovial tissue become embedded in the joint space, recurrent episodes of pain and locking may occur. Concentration of stress in the weight-bearing area of the hip joint increases the pressure per unit area, and the cartilage in the stress area of the femoral head and acetabulum is subjected to long-term abnormal stress wear. The degeneration of articular cartilage produces a large amount of cartilage debris, microcrystals, cartilage degradation particles and large molecules of inflammatory pain-causing factors, which remain in the joint cavity for a long time and irritate the synovial tissue, causing congestion and edema, hyperplasia and inflammatory exudation, resulting in fluid accumulation in the joint cavity, increased pressure and increased pain in the hip joint. Removal of pain-causing substances such as microcrystals and wear particles in the joint is important to interrupt the vicious cycle of inflammation, reduce pain and slow down the progression of the disease. The treatment of acetabular dysplasia includes conservative treatment, acetabular osteotomy, arthroscopic debridement and artificial joint replacement. In 1976, Fredensborg [4] followed 17 patients (19 hips) with a CE angle < 20° for 4 to 28 years, all of whom eventually developed osteoarthritis. The degree of arthritis was directly proportional to the degree of reduction in CE angle. Hipp et al [5] found that the contact area of the former was 26% less than that of the normal hip, and the pressure per unit area was 23% higher than that of the normal hip, when they performed pressure tests on 70 cases of acetabular dysplasia and 12 cases of normal hip. The pressure per unit area was 23% higher than that of the normal hip. The principles of treatment for adolescent and early acetabular dysplasia are: correcting the acetabular deformity, changing the acetabular accommodation of the femoral head, restoring the acetabular hyaline cartilage coverage, increasing the weight-bearing area of the hip joint, and changing the stress in the weight-bearing area of the acetabulum. In principle, the earlier the treatment, the better the results. The best age for acetabular osteotomy is during the school age, when the biological elasticity and plasticity of the bone tissue are at their best. However, the majority of adult patients with acetabular dysplasia are already suffering from severe osteoarthritis and have missed a good opportunity for acetabular osteotomy. In addition, acetabular osteotomy is technically difficult and demanding, with high risk of trauma and complications, such as sciatic nerve palsy, pseudarthrosis at the osteotomy site, osteotomy line incision into the joint, excessive hip abduction, heterotopic ossification, reduced abductor strength, and posterior column fracture [6]. For adult patients with Grade I-II acetabular dysplasia combined with osteoarthritis, who have failed conservative treatment, who have lost the opportunity for osteotomy or orthopedic surgery, or who do not undergo acetabular osteotomy, artificial joint replacement is not the preferred method due to age and many other factors. Most of these patients are treated symptomatically with anti-inflammatory and pain-relieving drugs, and most of them are not effective. Dorfmann et al [7] reported a 12-year experience of 413 hip arthroscopic procedures, of which diagnostic hip arthroscopy was performed in 68% of cases with unexplained hip pain, followed by hip osteoarthritis clearance and free body removal. Dienst et al [8] performed hip arthroscopy on 17 patients with acetabular dysplasia combined with osteoarthritis who had failed conservative treatment, and cleaned up the degenerated glenoid labrum and cartilage, hyperplastic synovium, intra-articular free bodies and bone superfluous, and achieved satisfactory results. We treated 32 patients with acetabular dysplasia combined with osteoarthritis by arthroscopic debridement, and the Harris score improved from (58.8±6.15) before surgery to (89.6±11.3) at the last follow-up, with an excellent rate of 85.7%. Since the anterior approach is prone to damage the femoral artery and femoral nerve [9], we use a lateral or anterolateral approach. The anterolateral approach should avoid the lateral femoral cutaneous nerve and mark the vascular and nerve paths before surgery to avoid injury. The subcutaneous tissue is separated with a hemostatic forceps after skin incision, and a blunt puncture cone is used to avoid damage to the articular cartilage. The lower extremity antagonistic traction is beneficial for joint gap retraction and surgical manipulation, but attention should be paid to the weight and duration of traction to prevent parietal pressure injury to the soft tissues of the perineal region from the perineal column [10]. Intra-articular injection of saline containing epinephrine can keep the operative field clear. In conclusion, although arthroscopic debridement cannot change the biomechanical factors of the acetabulum, for patients who have failed conservative treatment, are young, do not have a narrow joint space, and are not yet eligible for artificial joint replacement, arthroscopic debridement can not only further evaluate the lesions and cartilage wear in the hip joint, but also remove the degenerated and exfoliated cartilage fragments and broken glenoid lip flaps to relieve the symptoms of intra-articular strangulation.