Clinical and roentgenological studies on malalignment disorders of the patello-femoral joint. Part III: Lesions of the patellar cartilage and subchondral bone associated with patello-femoral malalignment.

This study was aimed at clarifying what mechanism of patello-femoral malalignment causes cartilage lesions and how the lesions are related to the symptoms. The study was composed of a laboratory experiment and clinical observations on 127 joints of 123 patients. In the clinical observations, cartilage lesions on the patella as well as on the groove and condyles of the femur were studied by performing either arthroscopy or open surgery. Changes of the subchondral bone of the patella were also examined through sky-line view roentgenograms to determine their relationship with cartilage lesions. From these observations, it was concluded that cartilage lesions are caused by shearing stresses produced by the abnormal motion of the patella due to malalignment, often accompanied by open or closed (to the joint cavity) subchondral lesions. The experiment showed that various types of cartilage-bone damage could be brought about depending on various combined factors of velocity and energy of the stressing force. Based on our theory, a reasonable treatment is presented.