The primary purpose of this study will be to determine if a CFs-Enriched Standard Care approach is an effective treatment for mechanical neck pain in terms of reducing pain and improving function. We hypothesize that a 4-week CFs-Enriched Standard Care approach will be superior to Standard Care alone in terms of patient-reported disability and pain, with measurements conducted using the Northwick Park Neck Pain Questionnaire and the Numeric Pain Rating Scale, respectively.

This will be an assessor-blinded, 2-group (1:1) randomized clinical trial aiming to enroll 94 participants with neck pain persisting for more than 4 weeks. Both groups will undergo 4 weeks of standard care twice weekly, following established clinical practice guidelines. In the intervention group, CFs will be enhanced, encompassing the physical, psychological, and social elements inherent in the clinical encounter, based on existing evidence.

The primary outcomes will encompass changes in Pain and Disability after 4 weeks of treatment, with a follow-up reassessment at week 12 post-treatment. Secondary outcomes will include changes in Active Range of Motion, Global Rating of Change, and Satisfaction with treatment. The change between groups after treatment and at the 12-week follow-up will be reported for all outcomes, considering the difference from scores recorded at baseline.

This study will be conducted at two sites in Buenos Aires, Argentina. Randomization will be stratified by site to ensure balanced allocation across centers.

The primary aim of this study is to determine if a Contextual Factors-Enriched Standard Care (CFs+SC) approach is an effective treatment for MNP in terms of reducing pain and improving function. We hypothesize that a 4-week Contextual Factors-Enriched Standard Care will be superior to Standard Care alone in terms of patient-reported disability and pain, with measurements conducted using the Argentine version of the Northwick Park Neck Pain Questionnaire (NPQ-AR) and the Numerical Pain Rating Scale (NPRS), respectively.

The secondary aims are:

• To determine whether CFs+SC is more effective than SC in terms of active range of motion (ROM) enhancement, global perceived effect (GROC), and satisfaction with treatment after the 4-week intervention.
• To determine if a CFs+SC approach is effective in treating MNP in terms of disability improvement, pain reduction, active ROM enhancement, global perceived effect (GROC), and satisfaction with treatment 12 weeks after a 4-week treatment plan.
• To explore differences in treatment credibility and expectations between the CFs+SC group and the SC group at both the 2-week and 4-week intervals.
• To investigate whether individuals identified with at least one negative psychosocial condition (such as anxiety, fear of movement, stress, catastrophizing, and depression) will experience greater benefits from the CFs+SC intervention compared to those without negative psychosocial conditions.

Consecutive patients meeting all inclusion criteria and none of the exclusion criteria will be randomly assigned in a 1:1 ratio to either the CFs+SC group or the SC alone group. Randomization will employ a blocked design with variable block lengths (2:4) and will be stratified based on recruitment site, baseline pain ('mild-moderate' or 'severe,' determined by whether they report between 3 and 7 points or ≥ 8 points on the baseline NPRS, respectively), and participants' expectations ('high' or 'low') regarding the effectiveness of standard care treatment.

The randomization process will be generated and conducted by personnel who will not be involved in data analysis or patient enrollment. The website www.randomization.com will be used for this process. To maintain allocation concealment during the study, sequential, numbered, and sealed opaque envelopes will be utilized. Patients will be allocated to one of two groups: a CFs+SC group and the SC group. Due to the nature of the study, blinding of both therapists and patients will not be feasible. The person in charge of data statistical analysis and the evaluators who will assess all participants' pre- and post-intervention assessments will be blinded to the allocated intervention.

Both groups will undergo 4 weeks of standard care twice weekly following established clinical practice guidelines, and including exercises, mobilization, manual therapy, education, and a neck wellness home care guide. In the intervention group, CFs will be enhanced, encompassing the physical, psychological, and social elements inherent in the clinical encounter, based on existing evidence.

At the onset of treatment, patients will receive a schedule outlining the dates of the next 8 visits. One day before each session, an individual not involved in the study will send a text message (SMS) reminder. Should a scheduled session be missed, it will be rescheduled. However, patients who miss two consecutive scheduled sessions will be deemed dropouts and analyzed using the intention-to-treat (ITT) approach, with the last observed value taken into consideration. Additionally, participants will be asked to refrain from undergoing any other treatments until the end of the 12-week follow-up period. During this period, participants are only permitted to adhere to the NWHCG. If a participant reports undergoing any other treatments, they will be considered as dropouts and analyzed using the ITT approach.

Due to slower-than-anticipated recruitment at the original site, a second recruiting site was incorporated on July 1, 2026, to reach the target sample size. Both sites apply identical eligibility criteria, intervention protocols, and outcome assessments. Physiotherapists at both sites completed the same training program described below, and adherence to the Manual of Treatment (MOT) is monitored equally across sites through the procedures described below

Physiotherapists will undergo a comprehensive training program comprising 8 hours of formal instruction, tailored to provide the necessary skills and proficiency for both therapeutic contexts under investigation. To ensure treatment fidelity, a Manual of Treatment (MOT) was developed. Therapist adherence to the MOT will be evaluated through self-assessment ratings provided by the therapists themselves. After each session, therapists will rate their adherence to the manual using a form specifically designed for this study. Additionally, monthly audits will assess compliance with the MOT, and frequent meetings with providers will be held to mitigate any deviations in provider adherence to the MOT, ensuring its consistency over time.

The sample size for this study was determined using a linear mixed effects model to account for within-subject correlation arising from repeated measures over time. The model includes fixed effects, such as treatment group (CF+SC and SC groups) and time points (baseline, 4 weeks, and 12 weeks after treatment), and recruitment site, along with the interaction between treatment group and time to assess potential changes in treatment effects over time. Random effects for individual subjects were also included to address repeated measures within the same subjects. Based on an assumed medium effect size (f2 = 0.15), 80% power, and a significance level of 0.05 (two-tailed), the estimated sample size required for this study was calculated to be 85 subjects. To accommodate a projected dropout rate of 10%, the sample size was adjusted, resulting in a final target sample size of 94 subjects (47 participants per group).

Outcomes will be analyzed on an ITT basis, with reporting of sample characteristics and descriptive statistics. Linear mixed models will be used for primary analysis to verify the differences between the average effects of interventions (CFs+SC and SC) in reassessments carried out 4 weeks after random allocation and 12 weeks after treatment, adjusting for recruitment site as a fixed effect given the stratified randomization. The differences between groups will be calculated by interaction terms of groups versus time. All statistical procedures will be performed using SPSS, developed by SPSS Inc., Chicago, IL, USA.

Trial procedures and evaluations will be conducted by trained personnel using paper-based Case Report Forms (CRFs), with implemented quality control measures. Subsequently, the data will be entered into an electronic database using MAWE® Data Collection Tools (www.mawetools.com). An independent data monitoring committee will oversee the entire data collection process to ensure its quality and integrity. Monitoring of the study will be overseen by MFA and FV at the original site, and by SS and POP at the second site, encompassing verification of adherence to predefined inclusion and exclusion criteria, monitoring overall study progress, and ensuring accurate data recording in CRFs. Auditing responsibilities will be carried out weekly by the principal investigator to ensure completeness and accuracy across critical study components, including participant consent forms, paper forms, and recruitment rates.

The trial will be conducted in compliance with the principles of the Declaration of Helsinki, Good Clinical Practice, and all applicable regulatory requirements. Ethical approval has been obtained from the Institutional Review Board (IRB) (#11695, approved on 15/03/2024). The principal investigator and researchers affirm no financial or other competing interests. Access to final trial data will be provided to designated individuals and authorized personnel, with any contractual restrictions transparently disclosed. Upon trial completion, results will be published in peer-reviewed journals, following authorship guidelines established by the ICMJE and CRediT framework.

Inclusion Criteria:

• Aged >18.
• Neck pain for more than 4 weeks without signs or symptoms suggestive of major structural pathology.
• Read, write, and understand the Spanish language.
• Signed consent form.

Exclusion Criteria:

• Numeric Pain Reporting Scale (NPRS) < 3 points (to ensure the exclusion of patients with minor disorders).
• Northwick Park Neck Pain Questionnaire (NPQ) < 10 points (to ensure the exclusion of patients with minor disorders).
• History of cervical spine trauma, fracture, or surgical procedures.
• Signs and symptoms of cervical myelopathy and/or cervical radiculopathy (to rule out cervical radicular pain, the Spurling Test, the Upper Limb Tension Test for the median nerve, and the Traction/Distraction test will be used).
• Red flags or serious pathologies, such as malignancy, inflammatory or rheumatic diseases, infections, and vascular conditions like cervical artery insufficiency.

Due to the nature of the study, blinding of both therapists and patients will not be feasible. However, to uphold the scientific validity of the study, specific descriptors and methodological details, such as terms like "placebo" or "CFs," have been intentionally excluded from the consent disclosure. To prevent any potential bias in participants' perceptions, information regarding the potential involvement of CFs in outcomes will not be provided. Instead, participants will be informed that the study aims to assess changes resulting from standard treatment for MNP. The person in charge of data statistical analysis and the evaluators who will assess all participants' pre- and post-intervention assessments will be blinded to the allocated intervention.