Ankle sprains represent a prevalent pathology among the pediatric population that can result in residual effects when treated incorrectly. However, there is a lack of scientific studies defining the most appropriate therapeutic approach. The hypothesis is that patients treated solely with general measures, without external device support, experience a faster recovery compared to those treated with ankle immobilization. A clinical trial will be carried out by randomly assigning patients to either the functional bandaging group or the control group (general measures only). Prospective follow-up will be carried out by a online survey send by SMS, checking the functionality of the injured ankle using 'the Oxford Ankle Foot Questionnaire for Children (OxAFQ-C)', in addition to pain control and patient satisfaction with the treatment.

Study Design: A randomized, parallel, open-label, multi-center clinical trial will be conducted at 3 intermediate-complexity hospitals. The study received approval from the center's ethics committee.

Procedure: Every patient presenting with ankle trauma will undergo assessment by the attending physician in the emergency department. The collaborating researchers of the different hospitals will participate in patient enrollment. In cases of grade I or mild sprains, patients and their guardians will be invited to participate in the study after a thorough explanation of the study's purpose and procedures. The severity of the sprain will be assessed using The West Point Ankle Grading System. Adequate analgesia will be ensured during the emergency department consultation.

Upon agreeing to participate in the study and signing the informed consent, randomization and assignment to either the control group or intervention group (receiving a bandage applied by nursing) will take place before the final discharge from the emergency department. The discharge report will specify the standardized treatment based on the assigned group. The attending physician will complete a physical study-specific record and will store the signed informed consent in a designated folder within the pediatric emergency department. The researcher in charge of each center will enter demographic data and variables obtained in the emergency department into a database hosted in the REDcap software. The data of the recruited patients should be entered in the REDcap database at least twice per week. The principal investigator or collaborators will review this REDcap database daily to check the recruited patients and prepare the SMS with the online survey to be sent. A coded patient number and the date of emergency care will be included in a database hosted in the center's electronic repository to determine the timing of follow-up. The SMS will be sent using the SMS sending system of the coordinating hospital of the study.

At 7, 14, and 30 days, the guardians of the patients will receive a SMS with a link that will direct them to the REDcap online survey. In case of no response to the initial attempt, another attempt will be made the following day, and, if no response is received in 48 hours, a telephone call will be made to the patients' guardians. Non-response at 72 hours will be recorded as a loss.

The data from the REDcap electronic database will be periodically reviewed by the principal investigator to monitore data entry and look for possible adverse effect.

Statistical Analysis: The sample size will be calculated assuming a difference of more than 10 points in the OXAFQ-C percentage scale value, estimating a standard deviation of 15, due to a previous study. Comparing two independent means with a bilateral test and a balanced random allocation (Group 1 size/Group 2 size ratio = 1), with a type I error of 5% (alpha risk) and a power of 80% (1-beta risk), and assuming a dropout of 30%, the calculated sample size will be 112 patients (56 in each group) for superiority analysis or 90 patients (45 in each group) for non-inferiority analysis.

Categorical variables will be described using percentages, and continuous variables will be presented as mean and standard deviation (SD) if normally distributed (Kolmogorov-Smirnov and/or Shapiro-Wilks) or as medians and interquartile ranges otherwise. Bivariable analysis of categorical variables will be performed using the Chi-square test or Fisher's exact test, and that of continuous variables will be done using the Student's T-test or its non-parametric equivalents.

Both intention-to-treat and per-protocol analyses will be conducted, assuming that some patients in the control group will use ankle support against recommendations. Finally, a non-inferiority analysis will be performed between both groups for both the primary variable and the degree of pain according to the visual analog scale (VAS) at different follow-ups.

All statistical tests will be considered with a significance level of 5%. The analysis will be conducted using the R software.

Missing Data:For all patients who do not complete at least two follow-ups, the electronic medical records of all public centers in the province where the study is conducted will be reviewed through the electronic Horus program to verify the absence of relevant adverse effects or diagnostic changes. Anyway, a worst-case scenario strategy will be used in the statistical analysis to assess the losses.

Inclusion Criteria:

• Diagnosis of grade I ankle sprain.
• Patients aged between 5 and 16 years.
• Less than 72 hours of evolution.
• Informed consent signed by guardians

Exclusion Criteria:

• Penetrating trauma.
• Associated fracture.
• Consultation more than 72 hours after the trauma.
• Developmental disorders (cerebral palsy, previous gait disorders, autism, etc.).
• Previous or concurrent disease that involves an increased risk of fractures (osteoporosis, bone diseases, etc).
• Previous ankle pathology.
• Impossibility of telephone contact

Due to the nature of the intervention, it will not be feasible to mask the received treatment at the time of care. Additionally, masking of the treatment group during clinical reviews will not be attainable, as some collected variables will be inherently related to the intervention itself. The data analyst specialist will also be unblinded to the group assignments.