[Patellofemoral instability].

Patellofemoral instability is an extremely limiting pathology in young and active patients. Anatomical reasons for patellar instability, such as high-riding patella, elevated distance from the tibial tuberosity to trochlear groove (TTTG), trochlear dysplasia, insufficient medial patellofemoral ligament (MPFL) and malpositioning of the axes and torsion can lead to chronic patellofemoral instability and must be thoroughly analyzed. The first dislocation can be treated conservatively, with the exception of an osteochondral defect. In the case of recurrent dislocation of the patella surgery is indicated, with good results regarding stability and less clear results regarding the influence on pain. The surgical approach is determined by the anatomical pathology. High-riding patella and elevated TTTG can be corrected by osteotomy of the tibial tuberosity and severe trochlear dysplasia by trochleoplasty. Insufficient MPFL can be reconstructed very successfully. The influence and correction of the axes and torsion are not yet fully understood and must be studied further.