Background:Foot orthoses have the potential to be an efficacious treatment for patellofemoral osteoarthritis (PFOA) but have not been evaluated in clinical trials in this population. This study aimed to determine the: (i) feasibility of conducting a randomised controlled trial (RCT) investigating the efficacy of foot orthoses in individuals with PFOA; and (ii) effects of foot orthoses versus flat shoe inserts on pain, function, and knee-related quality of life (QOL). Methods:This 6-week, single-blinded pilot RCT randomly allocated participants with PFOA to receive foot orthoses or flat inserts. The primary outcome of feasibility was determined via the following parameters: one participant recruited per week, 20% (35 h/week) adherence to the intervention, 50% log book completion rate, and < 20% drop-out, with results reported using descriptive statistics. Secondary outcomes included average and maximum pain severity (100 mm visual analogue scale), Anterior Knee Pain Scale, and Knee injury and Osteoarthritis Outcome Score, analysed using analysis of covariance. Results:Twenty-six participants (16 women; mean (SD) age of 60 (8) years) with PFOA were recruited. All feasibility parameters were exceeded, with three participants recruited per week, > 20% (37.2 [9.8] hours/week) adherence to the intervention, 69.2% (18/26) log-book completion, and 3.8% (1/26) drop-outs. The most common adverse events were arch irritation and shoe fit issues, which were more common in the foot orthoses group (67.9% versus 32.1%). There was a trend for the foot orthoses group to report larger improvements in average and maximum pain than the flat insert group, with the mean difference for maximum knee pain severity (21.9 mm, 95% CI - 2.1 to 46.0) exceeding the minimal clinically important difference (15 mm). The estimated sample size for a full-scale RCT is 160 participants. Suggestions to improve study design include a greater number of face-to-face follow-up appointments, a larger variety of foot orthoses to reduce rates of adverse events, and increasing follow-up time to determine long-term efficacy. Conclusion:This study supports the feasibility of a full-scale RCT to determine the efficacy of foot orthoses versus flat inserts in individuals with PFOA. Trial registration:The trial protocol was retrospectively registered with the Australian and New Zealand Clinical Trials Registry (ANZCTR number: 12616001287426).