To ascertain the efficiency of different techniques of arthroscopic therapy for gonarthritis and establish the relevance of the extent of chondromalacia, clinical and experimental studies were performed. In principle, the process of chondromalacia determines the course of the disease. Treatment of additional meniscus lesions temporarily leads to better clinical results, but after only a few months the symptoms caused by the arthritic process reappear. Compared with the temporary relief of complaints after debridement and lavage, smoothing with a xenon chloride excimer laser in grade II chondromalacia leads to statistically significantly better clinical results. Scanning electron microscopic studies confirm the extremely good smoothing. These studies permit clear statements as to the various methods of treatment and their application in the different grades of chondromalacia, thus leading to differentiated arthroscopic treatment of degenerative gonarthritis.