Assisted–Unassisted Walking Differential Across Three Configurations of a Powered Modular Gait Orthosis: Hip, Knee–Ankle–Foot, and Both Combined

Background/Objectives: Wearable powered gait orthoses are prescribed as assistive equipment, on the premise that torque at an impaired joint improves walking while the device is worn; the device also adds mass. Where a hip module and a knee–ankle–foot module can be worn together, the combined configuration places the mass of both on one limb, and whether its walking cost exceeds that of either module alone has not been tested under a common protocol. Methods: We analysed individual participant data from two previously published prospective studies, neither of which compared configurations. Forty-three adults with central neurological gait impairment, enrolled during 2024, were trained over six supervised sessions with a bilateral hip orthosis (HO, n = 13), a unilateral knee–ankle–foot orthosis (KAFO, n = 15), or both worn together (HKAFO, n = 15); the primary 6MWT analysis was performed on the complete-case subsample (n = 41, with HO n = 12, KAFO n = 14, HKAFO n = 15). The assisted–unassisted differential was computed per participant as (device-assisted − unassisted)/unassisted × 100; negative values indicate a shorter distance with the device. Results: No statistically significant baseline differences were detected across the three groups. The six-minute walk differential was larger for the HKAFO than for either single-region configuration at baseline (−24.9% versus −6.0% and −7.6%; Kruskal–Wallis p = 0.008) and after six sessions (−17.1% versus −5.9% and −4.3%; p = 0.012), whereas the two single-region configurations were indistinguishable at both assessments (p = 0.397 and 0.916). Short-distance gait speed did not differ between configurations (p = 0.290 and 0.457). Conclusions: The walking cost of the combined configuration was associated with a larger assisted–unassisted differential than that of either constituent module. We propose that this reflects the mass carried on a single limb rather than a shortfall in assistance, a reading these data support but cannot establish in the absence of kinematic or metabolic measurements. These findings should be regarded as hypothesis-generating and require prospective replication in a larger, adequately powered cohort.