Abstract: Objective: This study was to compare the effects of rest and low intensity exercise on tendon patella-patella junction (PPTJ) injury and patella with a cyclic loading animal injury model. Experiment design: 12 adult female New Zealand white rabbits were randomly assigned to a four-week cyclical load group (LD-RST,n=6) and a 8-week cyclical load group (LD-LI, n=6). During the experiment in the first 4 weeks, the two groups of rabbits received cyclical load of 7.17N/S·24 hours. After four weeks, the experiment on the LD-RST group was stopped and the load on the LD-LI group was changed into 4.2N/S·24 hours. After 8 weeks, tissues were collected from all the rabbits. The collected tissues were first scanned by Micro-CT and treated by H&E staining and then used for histological analysis by the image acquisition system. Results: There was no significant difference between the LD-LI group and the LD-RST group in the thickness of the fibrocartilage by H&E staining, and the collagen array in the LD-LI group is tighter and more regular than the LD-RST group. There is no significant difference in patellar microstructure between the experimental group and the control group. Conclusion: 4 weeks of rest can not promote the recovery of bone tendon junction injury. 4 weeks of low intensity of cyclic loading did not aggravate the damage and patella hyperplasia, and can promote the tendon reconstruction and repair.

Key words: Tendon Patella-patella Junction (PPTJ) Injury, Cyclical Load, Tendon Repair