In order to evaluate the biomechanics effectiveness of Anterior Tibial Tubercle Advancement (ATTA), we measured the contact site, contact area and stress distribution of the patellofemoral joint before and after ATTA procedure in eight fresh human cadaver knee joints with the Fuji Pressure Sensitive Film and the dyeing method. The result shows that the habitual contact site transfer from inferior to superior site after ATTA, which will prevent cartilage lesion site from stress extrusion and concentration, and perhaps reduce or relieve the patellofemoral pains. An assumption of "the patellofemoral pains caused by stress concentration at chondromalacia site" was thus proposed for above finds. after ATTA, the patallofemoral pressure was decreased only in 30°to 60°of knee flexion and became uneven or local high pressure in large degree of knee flexion. The contact area of patellofemoral joint was diminished with the increasing of knee fiexion. The tendofemoral contact appeared advancely at 60°of knee flexion after ATTA, which will affect the biomechanical behavior of patellofemoral joint.