Limitations of standard gait models for the precise and accurate evaluation of prosthetic knee joints regarding their functional quality, reliability, reproducibility and safety.

Abstract

Accurate motion analysis of prosthetic knee joints is essential for optimizing component design, improving gait restoration, and evaluating clinical performance. Sagittal knee angles and moments are key biomechanical parameters for assessing joint function. This study determined these parameters using various gait models and validated the results against sensor data from the prosthetic knee, supporting more reliable gait analysis and potential improvements in patient outcomes. Nineteen above-knee amputees walked at three self-selected speeds while gait was analyzed using optoelectronic cameras and force plates. Sagittal prosthetic knee moment and angle were calculated with four different models: Plug-in Gait, adapted Clinical Cleveland, 2D-model and a new 3D-model developed for analysis of transfemoral amputees. Simultaneously, prosthetic knee sensor angle and moment data were recorded. The mean sagittal knee angle and moment waveforms from all models closely match the sensor data, reflected by low root mean square errors, with the new developed model showing the smallest values. The most precise (most often lowest reproducibility coefficient) sagittal knee angle and moment is shown with the new model. For the sagittal knee angle the highest accuracy (most often lowest mean deviation) is also determined with this model. For the knee moment, the new model, the 2D-model and Plug-in Gait equally frequently show the smallest mean deviation. Relevant parameters of prosthetic knee joints can be determined using gait analysis, but not all models have the level of accuracy and precision required for evaluating prosthetic knee joints. The new model shows the most reliable data.