Abstract: BACKGROUND: There are many ways to reconstruct the patellofemoral ligament. Among them, the lateral insertion of the femur has a greater influence. At present, there are many ways to select femoral insertion points, but there are no conclusions. 
OBJECTIVE: Through the analysis of three-dimensional finite element software, the change of femoral reconstruction insertion position of medial patellofemoral ligament under different flexion states can analyze the stress of the patellofemoral joint to select a suitable femoral reconstruction insertion.
METHODS: CT data of normal knee joints of adults were obtained to import Mimics, Geomagic and Soildworks software to extract molds and add ligaments. The femoral insertion points of the ligament were the midpoint between the medial epicondyle and the adductor tubercle, the medial epicondyle, the adductor tubercle, the projection point from the top of the femoral intercondylar fossa to the medial condyle and 10 mm below the adductor tubercle. The mold added with ligament was imported into the mechanical software Ansys to analyze the stress of patellofemoral joint after reconstruction of different femoral insertion points using finite element analysis. 
RESULTS AND CONCLUSION: (1) When the knee flexion was 0° and 30°, the stress of patellofemoral joint at any femoral insertion point of reconstructed medial patellofemoral ligament was greater than that at other angles (60°, 90°, and 120°). No matter which position was used as the femoral insertion point, when the knee joint was flexed more than 30°, there was basically no difference in the contact stress between the patellofemoral joints. (2) At 0° and 30° of knee flexion, the patellofemoral contact pressure was the largest at the point of the adductor tubercle, and the contact force at the midpoint between the medial epicondyle and the adductor tubercle was the smallest. When the knee was flexed 30°, the midpoint between the medial epicondyle and the adductor tubercle, the projection point from the top of the femoral intercondylar fossa to the medial condyle, and 10 mm below the adductor tubercle as the insertion point showed no significant difference in the contact stress. (3) Results indicate that when reconstructing medial patellofemoral ligament, the best choice of femoral lateral insertion point is the midpoint between the medial epicondyle and the adductor tubercle. This point can effectively restore the stability of knee joint and delay the degeneration of joint and cartilage. 

Key words: patellofemoral dislocation, medial patellofemoral ligament, mesh generation, three-dimensional reconstruction, biomechanics, stress, finite element analysis, isometric reconstruction