Purpose The knee adduction moment (KAM) is a surrogate of medial compartment load during gait and is a target of conservative therapy for medial knee osteoarthritis (OA). Gait modifications have been shown to achieve KAM reduction, however, there has been limited experience with gait retraining methods outside the laboratory. In a previous study, we demonstrated that healthy subjects reduced KAM while walking with pressure-based feedback (PBF) that was designed to medialize center-of-pressure under the foot and impart a subtle gait modification. This prompted the current study, a longitudinal 6-week clinical trial of PBF for KAM reduction in subjects with mild to moderate medial knee OA. In this field study, subjects wear a fully integrated pressuredetecting shoe insole that communicates with a smartphone, which generates PBF in the form of auditory cues. Here, we report on the initial set-up, training, and response of subjects with medial knee OA to PBF in the lab. We tested the hypothesis that pressure-based feedback will reduce peak KAM (pKAM) in a significant majority of the subjects. We also compared the first peak of KAM (KAM1) and the second peak of KAM (KAM2) before and after PBF, and investigated potential adverse effect of PBF on knee flexion moment (KFM).