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On Transfemoral Prosthetic Knee Design for Natural Human Knee Motion

[ Vol. 13 , Issue. 1 ]


Wen-Tzong Lee*, Kevin Russell and Raj S. Sodhi   Pages 49 - 59 ( 11 )


Background: A transfemoral prosthetic knee is an artificial knee used by above-the-knee amputees. There are two major categories of transfemoral prosthetic knee designs: pin joint-based and polycentric designs. While pin joint-based knee designs only allow pure rotation of the knee, polycentric knee designs allow a combination of rotational and translational knee motion which is exhibited in natural knee motion.

Objective: This work presents both the recently-patented design process and the resulting design of a polycentric transfemoral prosthetic knee that approximates natural spatial human knee motion during flexion and extension.

Methods: The design process includes tibial motion acquisition, Revolute-Revolute-Spherical-Spherical linkage (or RRSS) motion generation, RRSS linkage axode generation and circle fitting. The polycentric transfemoral prosthetic knee design produced from this process includes a gear joint with a specific spatial orientation to approximate natural spatial human knee motion.

Results: Using the design process, a polycentric transfemoral prosthetic knee was designed to replicate a group of five tibial positions over 37.5° of knee flexion (the amount of knee flexion in a standard human gait cycle) with a minimal structural error.

Conclusion: The circular gear-based knee design accurately replicated natural spatial knee motion over the tibial position data given for a standard human gait cycle. The knee design method must be implemented over a broader sampling of tibial position data to determine if a circular gear-based knee design is consistently accurate.


Axode generation, circle fitting, four-bar spatial linkage, motion generation, polycentric knee, RRSS linkage, transfemoral prosthetic knee.


Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, Neipu, Pingtung 91201, Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102, Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102

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