Objective:To study mechanism of improvement of stress concentration on patellofemoral joint by stiletto needle releasing lateral patellar retinaculum guided by the theory of Jinshugu(筋束骨)and based on the finite element model of knee joint.and to elucidate the biomechanical mechanism of stiletto needle releasing changing patellar trajectory and reducing patellofemoral joint pressure.Methods:CT data of knee joint from a normal male(aged 29,heighted 171 cm,weighted 58 kg)was selected.Starting with construction of three-dimensional model of knee joint by using finite element software,the finite element model of knee joint with complete tendon and bone structures were established through several steps,such as geometric reconstruction,reverse engineering,meshing,material assignment and loading analysis.The loading condition was set as 500 N load on knee joint,and the average tensile stress of quadriceps femoris tendon was about 200 N.To simulate the release of lateral patellar retinaculum by stiletto needle at 30 and 90 position of knee flexion in finite element model separately,and to compare the improvement of stress concentration of patellofemoral joint by stiletto needle intervention under different knee flexion conditions.Results:The peak stress of patellofemoral joint and tibiofemoral joint decreased after stiletto needle releasing of patellofemoral lateral retinaculum compared with before intervention,which was(1)knee flexion at 30 degrees:patellar cartilage decreased by 0.498 MPa(decreased 9.06%),femoral trochlea decreased by 0.886 MPa(decreased 16.27%);(2)knee flexion at 90 degrees:patellar cartilage decreased by 0.558 MPa(decreased 8.6%),femoral trochlea decreased by 0.607 MPa(decreased 9.94%).Conclusion:Releasing lateral patellofemoral retinaculum with stiletto needle could effectively alleviate the stress concentration of patellofemoral joint and reduce local stress peak value,which it is helpful to improve patellar trajectory and make stress distribution more uniform.