A model of the swing phase of transfemoral (TF, above-knee) amputee gait was developed that gives a visual representation of the prosthetic limb’s kinematics in the sagittal plane. The model is one step in a larger goal to design high-performance prosthetic components for amputees under-serviced by current designs. The criteria for the design are defined, with primary design issues identified as floor clearance, stability and user requirements, including comfort and energy expenditure.

Model inputs were based upon motion analysis data collected for a single subject amputee wearing a Century XXII® five-bar prosthetic knee. Specific measurements were thigh trajectory and orientation, and the orientation of a driver linkage in the knee. The model was built using Working Model® Version 4.0. The motion of the pylon and foot were generated by the model, and these data were compared to the motion analysis data as a verification of the model’s accuracy and usefulness.

The maximum sole clearance height and timing agreed with experimental data within 2%, indicating that the model’s motion reflected the subject’s gait pattern. Furthermore, changes to knee fitting and design in the model generated altered foot trajectories consistent with trends described by an experienced prosthetist.

The model addresses the kinematic criterion of floor clearance. Relative changes in floor clearance for different knees with a consistent gait input indicate the relative compensatory effort required of the amputee to ensure the prosthetic foot clears the floor during swing. This, then, forms an objective basis for selection and optimization of prosthetic knee design.