Animal models of acute joint injury are useful for study of changes in joint tissues that may eventually lead to degradative disease. Our laboratory has developed a joint trauma model using a single blunt impact to the patellofemoral joint of rabbits and documented softening of retro-patellar cartilage and thickening of its underlying bone out to 12 months post-trauma. In the present study, we examined changes in these joint tissues out to 36 months post-impact. Forty-nine Flemish giant rabbits were impacted on the right patellofemoral joint and sacrificed at one of six times: 0, 4.5, 7.5, 12, 24, and 36 months post-impact. A 30% reduction in the compressive modulus of traumatized retro-patellar cartilage occurred at 4.5 months versus the contralateral, non-impacted limb and remained at this reduced level out to 36 months. The fluid permeability of traumatized cartilage also increased over time from baseline and versus the non-impacted limb. Tissue thickness increased slightly at 4.5 months and then decreased over time to a 45% difference from baseline at 36 months post-trauma. While impacted cartilage revealed a significantly greater length of surface fissuring than contralateral, non-impacted cartilage, no time-dependent changes were evident in this study. Moreover, the number and depth of these impact surface lesions did not change as a function of time. Finally, the histological analyses indicated that the thickness of underlying subchondral bone increased over time from baseline and versus that in the non-impacted limb. This long-term study suggested an association between a decrease in the characteristic time constant of traumatized cartilage and thickening of the underlying subchondral bone. Any potential cause and effect relationship, however, must be investigated in future studies. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
Ewers, B. J., Weaver, B. T., Sevensma, E. T., & Haut, R. C. (2002). Chronic changes in rabbit retro-patellar cartilage and subchondral bone after blunt impact loading of the patellofemoral joint. Journal of Orthopaedic Research, 20(3), 545–550. https://doi.org/10.1016/S0736-0266(01)00135-8