The purpose of the study was to determine whether prefabricated foot orthoses immediately reduce pain during functional tasks in people with patellofemoral osteoarthritis, compared to flat insoles and shoes alone.Eighteen people with predominant lateral patellofemoral osteoarthritis (nine women; mean [SD] age 59 years; body mass index 27.9 [3.2]kg/m2) performed functional tasks wearing running sandals, and then wearing foot orthoses and flat insoles (random order). Participants rated knee pain during each task (11-point numerical rating scales), ease of performance and knee stability (five-point Likert scales), and comfort (100mm visual analogue scales).Compared to shoes alone, foot orthoses (p=0.002; median difference 1.5 [IQR 3]) and flat insoles (p<0.001; 2 ) significantly reduced pain during step-downs; foot orthoses reduced pain during walking (p=0.008; 1 [1.25]); and flat insoles reduced pain during stair ambulation (p=0.001; 1 [1.75]). No significant differences between foot orthoses and flat insoles were observed for pain severity, ease of performance or knee stability. Foot orthoses were less comfortable than flat insoles and shoes alone (p<0.05).In people with patellofemoral osteoarthritis, immediate pain-relieving effects of prefabricated, contoured foot orthoses are equivalent to flat insoles. Further studies should investigate whether similar outcomes occur with longer-term wear or different orthosis designs.