| ① All patients reported persistent pain and crepitus of anterior knee when going up and down stairs and squatting.|
② The patellar medial shift  was less than 5 mm.
③ The anterior knee pain was induced by 30 degrees of knee flexion.
④ Patellar peripheral finger tenderness was touched on the surface of LR.
⑤ X-ray patella axial images showed obviously tilted outward patella, which was characterized by Wiberg type III or IV patellar .
⑥ The knee flexion 20 degree CT examination showed abnormalities of PTA and LPFA [13, 14].