Functional Trajectories of Low-Mobility Transfemoral Amputees with a K2-Specialized Microprocessor Knee: An Exploratory Prospective Observational Study

Background/Objectives: Despite growing evidence of benefit, microprocessor-controlled knees (MPKs) are not routinely integrated into standard rehabilitation pathways for low-mobility (K-Level 1–2) transfemoral amputees. This exploratory analysis aimed to characterize functional trajectories of low-mobility amputees associated with early versus delayed or no MPK provision in routine inpatient rehabilitation. Methods: This prospective observational multicenter study evaluated 24-week functional trajectories in low-mobility transfemoral amputees receiving standard inpatient rehabilitation at seven non-specialized centers in Germany. Participants were grouped post hoc into two groups: (1) early MPK provision (initial Kenevo use) and (2) delayed or no MPK provision (initial non-microprocessor knees with or without later transition). Patient-reported mobility (PLUS-M K2), health-related quality of life (EQ-5D-5L), and social reintegration (RNLI) were assessed across multiple time points during inpatient rehabilitation and follow-up. Analyses were descriptive and exploratory due to small sample size. Results: Nineteen participants were included. Across outcomes, the early MPK group showed more consistent improvements over time, whereas the delayed/no MPK group demonstrated more variable trajectories with less sustained gains. Conclusions: In this exploratory real-world cohort, early provision of a K2-specific MPK (Kenevo) was associated with more favorable functional trajectories compared with delayed or no MPK provision. Given the small sample size, post hoc group allocation, and potential confounding by indication, these findings should be considered hypothesis-generating. Larger prospective studies are required to evaluate the timing and role of MPK provision in low-mobility populations.