[Proliferative and metaplastic reactions as tentative reparatory processes in spontaneous arthritis in the mouse]

Performing histo-morphologic studies of knee joints in several hundred mice of the strains C57 black, STR/1N and MAGf, showing a disposition for spontaneous osteo-arthrosis, we found tentative reparative processes in many cases. There was a proliferation of cartilage and of the synovial membrane, mostly in the peripheral parts of the joints. The proliferating tissues were apparently moving towards an existing osteo-arthrotic focus. However, since cartilage and synovial tissues often became necrotic at the central, weight-bearing part of the joint they generally did not reach the defect. However, in a number of mice there were mostly small superficial defects in the joint cartilage filled with connective tissue of several grades of maturity. These regenerating spots were generally found in connection with the proliferating synovial membrane. In other animals there were fibrous vascularized pannus-like tissues, moving from the synovial membrane over the still normal cartilage towards a mostly centrally localized osteo-arthrotic ulcer. The pannus, like the inflammatory proliferating synovial membrane, often contained cartilaginous detritus. Attempts to regenerate arthrotic defects directly by local neoformation of cartilage, e.g. at the facies patellae of the femur, remained mostly without much success, showing only poor isles of chondrocytes, partially in cluster form. Interestingly, the menisci, like the synovial membrane, generally take part in the osteo-arthrotic process, also showing severe destructive alterations and rather often signs of regeneration, sometimes with cluster formation.