The aim of this retrospective study is to assess the extension apparatus function of the knee based on clinical, radiological, isokinetic and gait analysis data in patients after surgical treatment. There will be used physical examination, Lysholm-Tegner and Kujala scale for clinical assessment. Merchant and lateral X-ray pictures will be analyzed for patellar position verification along with isokinetic and gait evaluation to produce conclusions referring to the efficacy of the treatment. All subjects included in the study were treated with mpfl reconstruction. Follow-up longer than 2 years in all cases, about 45 patients included.