Meniscus Injury Induces Patellofemoral Osteoarthritis Development Mediated by Synovitis and Gait Kinematics: A Preclinical Study

To investigate whether meniscal injury leads to the development of patellofemoral (PF) osteoarthritis (PFOA) and to explore how synovitis and gait kinematics mediate this relationship. Fifty-four male Wistar rats (12 weeks old) were randomly assigned to the control, sham, or destabilized medial meniscus (DMM) groups. The rats were subjected to gait analysis to assess the kinematic changes at 2, 4, and 8 weeks postoperatively. Subsequently, the rats were euthanized, and their right knees were harvested for histological analysis. The Osteoarthritis Research Society International (OARSI) and modified Mankin (MM) scores in the DMM group were significantly higher than those in the control and sham groups at week 2 and significantly higher than those in the control group at week 4. The OARSI and MM scores in the sham group were significantly higher than those in the control group at weeks 2 and 4. The association between the DMM and OARSI scores was significantly mediated by the synovitis score and knee flexion angle at foot contact (proportion mediated: 58% and 10%, respectively). The association between the sham and OARSI scores was significantly mediated by the synovitis score and knee flexion angle (proportion mediated: 24% and 24%, respectively). DMM surgery induced articular cartilage damage in the PF joint. Synovitis and the knee flexion angle significantly mediated the association between DMM or sham surgery and PFOA development.