Abd‐Elmonem 2021.

Study characteristics
Methods	Randomised controlled two‐arm parallel trial
Participants	Initially recruited N = 134, excluded = 62 Study included: 72 children with flat feet, 36 in each group Age: 7 to 12 years old male and female Gender: 31 M, 35 F (M/F ‐ 15/18 in intervention group; 16/17 in sham group) Setting: out‐patient Physical Therapy Clinic of Faculty of Physical Therapy, Cairo University, Cairo, Egypt Inclusion criteria: (i) diagnosed (by an orthopedist) with asymptomatic flexible flatfoot, (ii) navicular drop more than 9 mm, (iii) grade III flatfoot Staheli Arch Index (midfoot width exceeding forefoot width) Exclusion criteria: (i) congenital deformities of the lower extremities (e.g. genu valgum, femoral anteversion), (ii) scar or osseous anomalies Baseline characteristics: age, mean (SD): 9.5 (1.02) in intervention group; 9.45 (0.76) in sham group
Interventions	Group 1: neuromuscular electrical stimulation and corrective exercise ‐ 4 months (3 sessions/week) Group 2: sham neuromuscular electrical stimulation and corrective exercise ‐ 4 months (3 sessions/week)
Outcomes	Assessments of Staheli’s arch index (through foot print), navicular drop (through navicular drop test), and radiographic indexes (through anterior‐posterior and medio‐lateral X‐ray) of both feet were performed before and after the intervention programmes
Source of funding	This research received no specific grant from any funding agency in the public, commercial, or not‐for‐profit sectors
Notes	Trial registration: NCT04410926
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The online Graph Pad software was used to allocate study participants".
Allocation concealment (selection bias)	Low risk	"The randomisation was carried out by an independent person, who was unaware of the study protocol and not otherwise in control of the study".
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	"All children/legal guardians, radiologist and researchers responsible for evaluations were blinded to participants’ allocation". However it is unclear whether the blinding was successful, as the trialists did not discuss the possibility that participants might have guessed their intervention based on whether they felt any discomfort related to the intervention or not.
Blinding of outcome assessment (detection bias) ‐ self‐reported outcomes (e.g., pain, function)	Low risk	There were no self‐reported outcomes
Blinding of outcome assessment (detection bias) ‐ objective outcomes	Low risk	Outcome assessors were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	3/36 (discontinued intervention = 3) in the intervention, and 3/36 in control group (discontinued intervention = 2; femoral fracture = 1) withdrew from the study and not included in the analysis
Selective reporting (reporting bias)	Low risk	trial registered, results for all pre‐specified outcomes reported
Other bias	Low risk	none apparent