The summation of forces on extensor mechanism should be zero according to equilibrium rules of forces before and after total knee arthroplasty based on constant extensor moment 计算得到髌骨形位参数变化前后与伸膝机构相关的动力学参数，包括股四头肌力、髌韧带力及髌股关节接触压力的变化。
In order to study the influence of some changes in patellar position and configuration on knee extensor mechanism in sagittal plane after total knee arthroplasty , a two - dimensional model of knee joint in sagittal plane based on crossed - four - bar linkage tibiofemoral joint model is developed , which includes patellofemoral joint model in addition 摘要为研究全膝关节置换术后髌骨部分形位参数的变化对伸膝机构性能的影响，建立了以交叉四连杆股胫关节模型为基础的、包含髌股关节模型的矢状面膝关节模型。
