[Etiopathogenetic significance of bone changes in spontaneous gonarthritis in the mouse]

In the C57 Black, STR/IN and MAGf strains of mice, which are prone to develop spontaneous osteo-arthritis of the knee, histomorphological examinations were made of the osseous parts of the joint. It was found that the number of animals with osteo-arthritis and with degenerative changes in the epiphyseal growth zone increases with age. There is nevertheless evidently no interrelation between the two phenomena. The same applies to the occurrence of osteoporosis and degenerative joint disease, since male C57 Black mice, for example, develop osteo-arthritis of the knee relatively often, but develop osteoporosis much more rarely, while the opposite is observed in the females. Moreover, among the juvenile joint degenerations in the STR/IN and MAGf strains, a high percentage of osteo-arthritis of the knee is found, but only a few instances of osteoporosis. The majority of the (relatively rare) idiopathic condylar necroses coincide with osteo-arthritis of the knee, but not vice versa. The development of osteosclerosis and degenerative cartilaginous defects is mostly (possibly always) a sequela and not the cause of osteo-arthritis of the knee. Malpositions are often associated with the development of osteo-arthritis of the knee. The C57 Black strain exhibits a certain tendency to develop genu valgum, and the STR/IN strain almost regularly shows genu varum; no distinct tendency is detectable in MAGf mice. Like the osteophytes, the enlarged menisci with obligatory ossification centres invariably seen in conjunction with osteoarthritis apparently help to compensate for the condylar incongruence caused by the degenerative process, prevent partial dislocations, and hence improve the stability of the joint.