Inclusion Criteria:  From September 2004 to January 2019, patients with lateral patella overcrowding syndrome treated by deputy chief physician Yang Yuping of the Department of Sports Medicine, Peking University Third Hospital  Exclusion Criteria:  From September 2004 to January 2019, patients with lateral patella overcrowding syndrome treated by deputy chief physician Yang Yuping of the Department of Sports Medicine, Peking University Third Hospital