OBJECTIVE: To investigate the arthroscopic treatment of patellofemoral osteoarthritis in the knee. METHODS: Arthroscopic surgery was used to completely release the lateral support band, remove the hypertrophic synovial membrane, flush and clean the joint cavity, and decide on the microscopic tightening of the medial support band or tightening under direct vision with incision, and observe the patellar motion trajectory and the expansion and balance of the patellofemoral joint gap before and after the release while loosening or tightening, until the motion trajectory was close to normal. Results: 35 patellofemoral joints were followed up for 1 to 5 years, with an average of 3.5 years. 18 cases (78.3%) were excellent. Good 4 cases, accounting for 17.3%. Lysholm score was 36-72 (mean 53) before surgery and 82-100 (mean 90.8) after surgery, with a mean improvement of 32.6 points (P < 0.01 =). Conclusion: Stability reconstruction is important in the treatment of patellofemoral osteoarthritis, and only by correcting joint alignment disorders and eliminating abnormal stresses can symptoms be fundamentally relieved. The patellofemoral joint is the site of osteoarthritis in the knee joint, and patellofemoral osteoarthritis is a common cause of knee pain. However, due to the anatomical structure and biomechanics of the patellofemoral joint, there is still some clinical debate on the choice of patellofemoral osteoarthritis surgery and the judgment of its efficacy. The incidence of knee osteoarthritis is high, accounting for 73% of the entire osteoarthritis, and patellofemoral osteoarthritis occupies a high rate in knee osteoarthritis, and the incidence of patellofemoral joint stenosis instability is even higher, which seriously affects people's quality of life, reviewing our department since 2000 to apply arthroscopic surgery to treat patellofemoral osteoarthritis 40 cases of 46 knees, all obtained good results. Clinical data 1. General information In this group, there were 13 male and 27 female cases, aged 54-75 years, with an average of 58.4 years. 6 cases had double knees and 34 cases had single knees, with a total of 46 knees. Symptoms and signs: 40 patients had a disease duration of 3 to 15 years and non-surgical treatment was ineffective. 2. Clinical manifestations 46 knees were painful when moving, affecting normal life and unable to participate in normal labor. Main symptoms: ① patellofemoral joint pain, aggravated by half squatting and going downstairs, inability to walk uneven night paths and restricted activities; ② friction sounds under the patella; ③ pseudo-coital locking of the patellofemoral joint. The main signs: ① joint swelling; ② patellar tenderness; ③ positive patellar grinding test; ④ patellar lateral edge tenderness; ⑤ patellar mobility was reduced, and passive medial movement of the patella was limited at 30° of knee flexion; ⑥ patellofemoral joint gap was wide medially and narrow laterally in knee extension position, and the patella was tilted to the lateral side; ⑦ patella sliding trajectory was abnormal during knee extension and flexion activities. In four cases, the knee joint was swollen, the patellar grinding test was positive, the knee joint activity was restricted, with an average restriction of 54° in flexion and 15° in extension, and the muscles of the thigh and lower leg showed different degrees of atrophy. 3, imaging data X-ray projection of the knee joint in standing front and lateral position and axial patella at 30° of knee flexion showed degenerative changes and osteophytes in the whole knee joint. The patella is displaced laterally, the patellofemoral joint gap is wide inside and narrow outside, and there is osteophyte hyperplasia and subchondral bone sclerosis. Axial patellar radiographs showed asymmetric height of the left and right patellofemoral joint gaps, partial patellar tilt, patellar subluxation, partial loss of joint space, and increased density and sclerosis of the patellofemoral joint surface. In 15 cases, 3D CT scans showed narrowing of the patellofemoral joint gap, hardening of the articular cartilage, and unevenness and roughness of the joint surface. RESULTS: In 23 of 40 cases, 35 operated knees were followed up for 1 to 5 years, with an average of 3.5 years, and we evaluated them according to the following assessment criteria: excellent: the pain of knee movement disappeared, the joint mobility was normal, and the patient was able to walk freely, and a few patients had occasional mild pain during activity, but it disappeared rapidly after rest, and the patient was satisfied. There were 18 cases, accounting for 78.3%. Good: The pain of knee joint activity disappeared, but there could be pain when moving more, and the pain was obvious when going up and down stairs and squatting, and the joint was slightly swollen, which disappeared after resting and taking painkillers, and daily life was not greatly affected, 4 cases (17.3%). Poor: No significant improvement in symptoms and signs after surgery, still affecting life and work, the patient was not satisfied, a total of 1 case, accounting for 4.4%. 36-72 points (mean 53 points) in Lysholm knee score method before surgery, 82-100 points (mean 90.8 points) after surgery, the mean improvement increased by 32.6 points (P < 0.01). Postoperative imaging data showed no re-dislocation of the patellofemoral joint, one case had transient anterior knee pain and discomfort, but it did not affect joint function, no vascular nerve injury, no infection, patellar ligament tear and fracture, etc. Discussion: Patellofemoral osteoarthritis is a common disease that can occur alone or with tibiofemoral arthritis, more in women than men. Patellofemoral osteoarthritis is one of the major lesions of osteoarthritis of the knee, mainly due to pathological changes associated with sclerosis and destruction of the patellofemoral articular surface, unevenness of the articular surface, exposure of the subchondral bone plate, degeneration of the articular cartilage, patellar instability and recurrent chronic lateral subluxation. The etiology of patellofemoral osteoarthritis can be divided into 2 types: primary and secondary. The primary type is the unexplained degeneration of patellar cartilage, while the secondary type factors are patellofemoral injury, dysplasia, chondromalacia, and patellofemoral malalignment. Abnormal lower extremity force lines and patellar trajectories are also common causes of patellofemoral arthritis. Regardless of the etiology, the pathology causing patellofemoral joint injury is the same. Long-term patellar instability and repeated chronic lateral subluxation lead to imbalance of stress on the cartilage surface of the patella, which not only increases the lateral side load and decreases the medial side pressure, but also increases the shear and instability of the patellar center, resulting in softening and destruction of the articular cartilage surface, external displacement of the patella leading to contracture of the lateral soft tissue and imbalance of the medial and lateral forces, resulting in the occurrence of distraction osteochondrosis of the lateral edge of the patella and pressure osteochondrosis of the lateral femoral condyle edge. The patellofemoral joint alignment disorder is a result of the Patellofemoral joint disorder is an important imaging basis for patellofemoral joint instability degeneration, which is classified by foreign scholars as simple patellar tilt, simple patellar subluxation, and patellar tilt combined with subluxation. Patellofemoral arthralgia has long been thought to be related to the destruction of the cartilage surface of the patella by softening. In the treatment of patellofemoral osteoarthritis with arthroscopic debridement, irrigation and simple lateral release of the support band, the pain symptoms can be relieved to some extent after surgery, but most patients have a recurrence of symptoms within a short period of time. We take into account the changes in biomechanics of patellofemoral osteoarthritis and its pathological changes, and use thorough release of the lateral support band, excision of the hypertrophic synovium, flushing and cleaning of the joint cavity. The patellar motion trajectory and patellofemoral joint gap expansion and balance before and after the release were observed under the microscope while releasing or tightening, until the motion trajectory was close to normal. This procedure corrects the abnormality of the knee extension device, relieves the pressure on the patellofemoral joint, preserves the patella, and balances the medial and lateral forces of the patella. The advantages of this procedure are: 1. A new combination of upper and lower patellar distraction axes restores normal biomechanical contact of the patellofemoral joint surface. 2, Increase the variable tensile stress of the patella inward to counteract or offset the lateral tension of the patellar ligament, the outward movement of the patella causing a lateral semi-high stress and a medial semi-low stress on the patellar cartilage surface, restore the normal sliding of the patella in the coronal and sagittal plane of the femoral talus and intercondylar groove of the femur, and restore the normal distribution of biomechanical stress on the patellofemoral joint surface. 3. The patellofemoral joint has different degrees of quadriceps atrophy and decreased knee extensor muscle strength. The simple stability reconstruction does not destroy the normal extensor muscle structure and facilitates early postoperative rehabilitation exercises, thus strengthening the stability of the patella and knee joint. Early postoperative activity reduces joint fiber adhesions and stiffness, light surgical trauma, rapid recovery, and significant symptom improvement. Passive exercise of the knee joint should be performed after 4-7 d postoperatively to establish a new patellar motion trajectory which is very important, but premature joint activity can affect the stability of the joint. We have not seen medial or intra-articular dislocation of the patella during our follow-up. In the pathogenesis of early patellofemoral arthritis, a mild outward displacement of the patella causes a stress imbalance on the cartilage surface of the patella and increases the lateral half-load and decreases the medial half-load, resulting in patellar cartilage softening and early patellofemoral arthritis. Mild outward displacement of the patella causes early patellofemoral arthritis, which will eventually develop into advanced patellofemoral arthritis if it is not treated in a timely manner. In severe patellofemoral arthritis, knee extension and flexion functions are lost, and patellar resection was usually performed in the past, but it often leaves a weakened knee extension muscle, especially the last 10° to 15° of knee extension cannot be completed well. Therefore, the main goal of early arthroscopic surgical treatment is to reduce the lateral half-load of patellar cartilage and increase the medial half-load so that the patellofemoral articular surface becomes fully loaded. There are many treatment methods, most of which are to change the patellar tension axis and increase the patellar inward tensile stress, but they cannot guarantee the normal sliding of the patellar cartilage surface in the coronal and sagittal plane of the femoral talus and intercondylar groove of the femur, nor can they guarantee the normal distribution of biomechanical stress in the patellofemoral joint. We believe that support band release is a soft tissue procedure, which is less invasive when performed arthroscopically and is suitable for stage I and I-II cartilage lesions. However, given the relatively short follow-up time of the cases in this study, the long-term efficacy needs to be further observed. Patellar osteotomy with coronal and sagittal osteotomy is suitable for those with patellofemoral dysplasia, which is not carried out much due to the small number of cases in China. This study concluded that stability reconstruction is important in the treatment of patellofemoral osteoarthritis, and that joint pain is mainly caused by stress, not by the cartilage itself, and that only by correcting joint alignment disorders and eliminating abnormal stress can symptoms be relieved.