Comparison of The Effects of Single-Site and Concurrent Transcranial Direct Current Stimulation (M1, DLPFC) on Pain Intensity, Balance, Motor Function and Quadriceps Muscle Strength in Female Students with Patellofemoral Pain Syndrome

The aim of this study is to compare the effects of transcranial direct current stimulation over the primary motor cortex (M1) alone with simultaneous stimulation of the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) on pain intensity, balance, motor function, and quadriceps muscle strength in female students with patellofemoral pain syndrome.

This is a randomized, double-blind, parallel-group, controlled clinical trial involving 42 female students with patellofemoral pain syndrome. Participants will be allocated by an independent researcher using simple randomization with a Random Allocation Software into three groups of 14 participants each.

This study will be conducted at the Faculty of Sport Sciences, Razi University, Kermanshah. After written informed consent, participants will be randomly allocated to three groups of 14. Group 1 will receive M1 stimulation, Group 2 simultaneous M1 and DLPFC stimulation, and the Control Group sham stimulation. Stimulation will be delivered at 2 mA for 20 minutes over six sessions. The Control Group will receive sham stimulation under similar conditions.

Participants in this study will be female students aged 18–35 years with patellofemoral pain syndrome and a minimum anterior knee pain intensity of 3. Individuals with a history of knee injury or surgery, other knee pathologies, patellar dislocation, pregnancy, psychiatric disorders, use of nonsteroidal anti-inflammatory drugs (NSAIDs) within the past week, or treatment for knee pain within the past 6 months will be excluded from the study.

Experimental Group 1 (M1 stimulation), Experimental Group 2 (M1 + DLPFC stimulation), and Control Group (sham stimulation)

Pain intensity; Balance; Forward Step-Down Test score; Physical function; Quadriceps muscle strength

Eligible participants were randomly allocated using simple randomization to three groups of 14 participants each: Experimental Group 1 (receiving transcranial direct current stimulation [tDCS] over the primary motor cortex), Experimental Group 2 (receiving simultaneous tDCS over the primary motor cortex and dorsolateral prefrontal cortex), and the sham group (receiving sham stimulation without an actual therapeutic effect). The random allocation sequence was generated using the Random Allocation Software by an independent individual who was not involved in the study. For allocation concealment, a random code was assigned to each allocation, and the codes generated from the randomization sequence were placed separately in opaque, sealed envelopes. After each eligible participant entered the study, the envelopes were made available to the participant, who randomly selected one envelope. After opening the envelope, the code inside was matched with the randomization list, and the participant’s assigned group was determined. Thus, the participant’s selection of an envelope resulted in random allocation to one of the three groups, and group assignment could not be predicted or observed before the envelope was selected. The unit of randomization was the individual participant, and no block, stratified, or cluster randomization was used.

Outcome assessors and participants were blinded to the type of intervention administered. Prior to the commencement of the study, to ensure allocation concealment, the codes generated from the random allocation sequence by an independent individual who was not involved in the study, using the Random Allocation Software, were placed separately in opaque, sealed envelopes. After each eligible participant entered the study, the participant randomly selected one of the envelopes. After opening the envelope, the code inside was matched with the randomization list, and the participant’s assigned group was determined. Thus, group allocation could not be observed or predicted by the participant or the outcome assessor before the envelope was selected and opened. The interventions across the study groups were similar in terms of administration procedure, number and duration of sessions, and conditions of stimulation, with the only difference being the stimulation site in the active intervention groups. In the sham group, sham stimulation was administered using the same procedure. Therefore, participants were unaware of the type of intervention they received and their group allocation. Since participants were also unaware of the type of intervention administered to the other groups, they could not determine which group they had been assigned to.

To protect the confidentiality and privacy of participants’ information and due to restrictions on sharing individual-level data, the raw and individual participant data will not be made publicly available. The overall study results will be reported in an aggregated form, without any possibility of identifying individual participants.