Histopathological Effects of Loading on Cartilage Repair in a Rat Full-thickness Articular Cartilage Defect Model

[Purpose] We investigated effects of loading on cartilage repair in rat full-thickness articular cartilage defects and histopathologically analyzed the healing process of the defect. [Subjects] A total of 40 male 9-week-old Wistar rats were used. [Methods] Full-thickness articular cartilage defects were created over the capsule at the loading portion in the medial condyle of the femur. Twenty rats were randomly allocated into each of a loading group and non-loading group. Twenty rats from these two groups were later randomly allocated to each of 2 groups for evaluation at 1 and 2 weeks after surgery. At the end of each period, knee joints were examined histopathologically and statistically. [Results] The surface of the repair tissue in the loading group was irregular and discontinuous, while that in the non-loading group was smooth and continuous. The results of the statistical analysis showed that the difference in the surface between the loading group and non-loading group was significant. The defects in the both groups spontaneously resurfaced with a mixture of hyaline cartilage and granulation tissue, and some remnants of articular cartilage with aseptic necrosis were contained in the repair tissue. [Conclusion] We concluded that loading in the early phase of an articular cartilage defect may be accompanied by a certain danger for the repair tissue.