The New Genium X4 Microprocessor-controlled Knee Joint: How Do Users Benefit from Entirely New Functions in Everyday Life?

Background: A successor to the Genium X3 microprocessor-controlled knee joint has been developed, aiming to offer innovative improvements enhancing patient mobility and safety. Entirely new functions were implemented that users may benefit from in daily-life situations, including walking initiation, walking backwards, and walking up ramps. Objective: This study aimed to compare the Genium X4 to the previous model regarding safety and performance. Methods: In a combined clinical and biomechanical pilot trial, eight current Genium and Genium X3 users (six unilateral, two bilateral; K3–K4) were enrolled. Subjects were fit with the Genium X4 to evaluate the knee joint in everyday life. Patient-reported outcomes were collected with the Comparative Activities of Daily Living Questionnaire and a study-specific questionnaire. Biomechanical analysis was conducted in comparison with the Genium X3, including level ground walking, walking initiation, walking backwards and walking up ramp (10°). Results: Patient-reported outcomes showed higher ratings for X4 in both safety and performance compared with Genium/X3. Of 45 activities evaluated in the Activities of Daily Living Questionnaire, 12 were rated as easier and 13 as safer, exceeding clinical relevance threshold. All subjects preferred the Genium X4 over their Genium/X3 and frequently reported advantages from the new functions. In the study-specific questionnaire, the tasks walking initiation (7/8), walking backwards (6/8), and walking up ramps (5/8) were rated as better. In the biomechanical analysis, several improvements were observed. Initiating walking with the prosthetic side could be performed with a significantly higher knee flexion angle as well as reduced compensatory movements of the pelvis and upper body. When walking backwards, anterior–posterior ground reaction force momentum was significantly higher during prosthetic side push off, indicating an improved acceleration phase. Walking up ramps was performed with a significantly higher knee flexion angle at initial contact on the prosthetic side and reduced compensatory movement on the contralateral ankle. Conclusions: The Genium X4 demonstrated significant improvements, providing users with greater safety, enhanced functionality, and an improved user experience in daily life.