HAPPi Kneecaps! A double-blind, randomised, parallel group superiority trial investigating the effects of sHoe inserts for adolescents with patellofemoral PaIn: phase II feasibility study

Background: Patellofemoral pain (PFP) affects one-third of adolescents and can persist into adulthood, negatively impacting health and quality of life. Foot orthoses are a recommended treatment for adults with PFP, but have not been evaluated in adolescents. The primary objective was to determine the feasibility of conducting a full-scale randomised controlled trial (RCT) evaluating effects of contoured, prefabricated foot orthoses on knee pain severity and patient-perceived global change, compared to flat insoles. The secondary objective was to describe outcomes on a range of patient-reported outcome measures. Methods: We recruited adolescents aged 12–18 years with PFP of ≥2 months duration into a double-blind, randomised, parallel-group feasibility trial. Participants were randomised to receive prefabricated contoured foot orthoses or flat shoe insoles, and followed for 3 months. Participants and outcome assessors were blinded to group allocation. Primary outcomes were feasibility of a full-scale RCT (number of eligible/enrolled volunteers; recruitment rate; adherence with the intervention and logbook completion; adverse effects; success of blinding; drop-out rate), and credibility and expectancy of interventions. Secondary outcomes were patient-reported measures of pain, symptoms, function, quality of life, global rating of change, patient acceptable symptom state, and use of co-interventions. Results: 36 out of 279 (12.9%) volunteers (27 female, mean (SD) age 15 (2) years, body mass 60 (13) kg) were eligible and enrolled, at a recruitment rate of 1.2 participants/week. 17 participants were randomised to receive foot orthoses, and 19 to flat insoles. 15 participants returned logbooks; 7/15 (47%) adhered to the intervention. No serious adverse events were reported. 28% (10/36, 4 pandemic-related) of participants dropped out before 3 months. Blinding was successful. Both groups found the inserts to be credible. Conclusions: Based on a priori criteria for feasibility, findings suggest that a full-scale RCT comparing contoured foot orthoses to flat insoles in adolescents with PFP would not be feasible using the current protocol. Prior to conducting a full-scale RCT, feasibility issues should be addressed, with protocol modifications to facilitate participant retention, logbook completion and shoe insert wear. Trial registration: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12619000957190. Date registered: 8/07/2019.