Effects of chronic ankle instability on ipsilateral knee cartilage degeneration in mouse model

Objective To explore the effects of chronic ankle instability (CAI) on ipsilateral knee cartilage degeneration and the coupling relationship between the two joints through mouse model. Methods Thirty C57BL/6J mice were divided into the Sham group, the CAI group, and the destabilization of medial meniscus (DMM) group. They were respectively subjected to sham surgery, anterior talofibular ligament and calcaneofibular ligament transection, and medial meniscus resection. The degeneration of knee cartilage was evaluated through kinematic experiments, imaging examinations and histopathological analysis within 12 weeks post-operation. Results The kinematic experiments exhibited significantly increased passing time and number of slips for CAI group compared to DMM group and Sham group during crossing the balance beam; the step length and step width of CAI group were also larger. Imaging examination revealed obvious osteochondral defects and osteosclerosis of the femoral condyles both in CAI group and DMM group at 12 weeks post-operation. However, the DMM group was more severely affected than CAI group, as its bone mineral density and bone volume fraction were both higher than CAI group. Histopathological analysis exhibited thinner cartilage layer, less chondrocytes and more disordered collagen fibers in DMM group than CAI group at 6 and 12 weeks post-operation. The modified Mankin score and OARSI score of DMM group were also significantly higher than CAI group, while both groups were higher than Sham group. Conclusions CAI can cause cartilage degeneration of ipsilateral knee joint in mouse model, there is a coupling relationship between ankle joint and knee joint.