In the differential diagnosis of femoropatellar joint disease, three conditions must be considered: (1) peripatellar irritation; (2) chondromalacia of the patella; (3) femoropatellar arthrosis. In approximately 90% of the cases, peripatellar irritation and chondromalacia of the patella can be kept under control by active extension and strengthening exercises for the femoral flexor and extensor musculature. In therapy-resistant cases, arthroscopic surgery can provide the opportunity to influence the pathological gliding process positively. The operative procedure is planned on the basis of clinical and radiological examinations and computed tomography investigations. Dysplasia of the patella, including a lax patella, not only requires lateral release, but also medial tightening whereas patellar insufficiency can be treated successfully by lateral release alone. In our new staging procedure, chondromalacia and femoropatellar arthrosis are differentiated. Stage III chondromalacia is simply smoothed out via arthroscopy. In the treatment of femoropatellar arthrosis, on the other hand, restitution of the cartilage defect is of most importance. The age of the patient and staging of the cartilage defect determine which therapeutic procedure is to be used. The "release" operations in the treatment of femoropatellar arthrosis serve to relieve the damaged cartilage area and depend on the axial positioning of the knee joint.