OBJECTIVE To evaluate the effects that modern shoes have on gait and lower extremity joint loads in osteoarthritis (OA). METHODS Gait analyses were performed on 75 subjects with knee OA while they were wearing their everyday walking shoes and while they were walking barefoot. The trials involved optoelectronic detection of external markers during ambulation over a multicomponent force plate, and were matched for speed. Comparisons were made of gait parameters and joint loading during trials in which the subjects walked while wearing shoes and while barefoot. RESULTS Peak joint loads at the hips and knees significantly decreased during barefoot walking, with an 11.9% reduction noted in the knee adduction moment. Stride, cadence, and range of motion at the lower extremity joints also changed significantly, but these changes could not explain the reduction in the peak joint loads. CONCLUSIONS Shoes may detrimentally increase loads on the lower extremity joints. Once factors responsible for the differences in loads between with-shoe and barefoot walking are better delineated, modern shoes and walking practices may need to be reevaluated with regard to their effects on the prevalence and progression of OA in our society.