BACKGROUND: Although overuse-induced patella-patellar tendon junction injury is a common disease, its pathogenesis and healing mechanism remain unclear.OBJECTIVE: To establish an overuse-induced injury animal model by a repetitive traction at the patellar tendon insertion,and to explore its pathogenesis and healing mechanism based on histomorphology and growth factor expression levels.METHODS: Twenty-eight New Zealand rabbits were randomly divided into four groups: the rabbit left and right posterior limbs without any intervention as controls (n=4); cyclic loading training targeting the left posterior limb was done in model,healing and training groups (n=8 per group) for 4 weeks. Afterwards, the rabbits in the model group were killed immediately, rabbits in the healing group relaxed for another 4 weeks and then were killed, while rabbits in the training group were subjected to 4-week low-intensity training. The histological changes and growth factor expression levels during patella-patellar tendon junction injury and healing after load training were observed.RESULTS AND CONCLUSION: Compared with the control group, in the model group, the cells and collagenous fibers arranged in disorder, and the tidemark disappeared. The healing and training groups healed incompletely, but showed better histological changes than the model group. The thickness of fibrocartilage and basic fibroblast growth factor level in the control group were significantly lower than those in the other three groups (P < 0.05). The cell density and vascular endothelial growth factor level in the model group were significantly higher than those in the control and healing groups (P < 0.05). These results show that the animal model of overuse-induced patella-patellar tendon junction injury cannot return to normal after 4 weeks of rest, but the low-intensity training is conductive to healing quality.