Faculty of Health,University of Witten/Herdecke;
Depart-ment of Orthopedics,Trauma Surgery and Sports Medicine,Johanna Etienne Hospital;
Joint Center Hilden and Ruhr-University Bochum;
Center of Trauma and Orthopedic Surgery,Jena University Hospital;
Trochlea dysplasia; Medial-patellofemoral ligament; Patellofemoral instability; Patella dislocation; Trochleoplasty;