Pes planus, also known as flatfoot, is a common foot deformity that can affect the biomechanics of the lower limbs. However, its relationship with neurological conditions has not been studied extensively. Restless Legs Syndrome is a neurological disorder characterized by uncomfortable sensations in the legs and an urge to move them, especially during periods of rest, which can negatively affect sleep quality.

The aim of this multicenter cross-sectional study, conducted at Etlik Zübeyde Hanım Women's Health Training and Research Hospital, Etlik City Hospital in Ankara, and Yozgat City Hospital, is to determine the frequency of Restless Legs Syndrome in patients diagnosed with pes planus and to examine its effects on pain, emotional status, sleep quality, and quality of life. The study included 122 patients aged between 18 and 65 years with clinically diagnosed pes planus, and 120 healthy individuals matched for age and sex. Participants were assessed using the International Restless Legs Syndrome Study Group Diagnostic Criteria and Severity Rating Scale for Restless Legs Syndrome, the Visual Analog Scale and Foot Function Index for pain and foot function, the Hospital Anxiety and Depression Scale for emotional status, the Pittsburgh Sleep Quality Index for sleep quality, and the Short Form-36 Health Survey for quality of life.

Pes planus, commonly known as flatfoot, is a frequent foot deformity characterized by a lowered medial longitudinal arch, which can affect lower limb biomechanics and overall posture. While its mechanical effects on the musculoskeletal system have been widely studied, the potential neurological and psychosocial implications of pes planus remain insufficiently explored.

Restless Legs Syndrome (RLS) is a neurological disorder marked by an uncontrollable urge to move the legs, often accompanied by unpleasant sensations. Symptoms typically worsen during rest or inactivity and can lead to significant sleep disturbances and reduced quality of life.

This multicenter cross-sectional observational study was designed to investigate the prevalence of RLS among patients clinically diagnosed with pes planus, and to evaluate the impact of RLS on pain severity, emotional well-being, sleep quality, and overall health-related quality of life.

The study was conducted between December 2024 and July 2025 at three tertiary care centers: Etlik Zübeyde Hanım Women's Health Training and Research Hospital, Etlik City Hospital in Ankara, and Yozgat City Hospital. A total of 242 participants were recruited, including 122 patients with clinically confirmed pes planus and 120 age- and sex-matched healthy controls without foot deformities or leg pain.

Inclusion criteria for patients were age between 18 and 65 years and a clinical diagnosis of pes planus by a physical medicine and rehabilitation specialist, based on physical examination. Exclusion criteria included the presence of systemic diseases such as diabetes mellitus, hypothyroidism, chronic renal failure, neuropathies, rheumatological conditions, history of foot surgery or fractures, and other conditions potentially affecting pain perception or neurological status.

Data collection included demographic information (age, sex, body mass index, educational status, smoking and alcohol use) and clinical variables (duration and severity of leg pain). The presence and severity of RLS were assessed using the International Restless Legs Syndrome Study Group Diagnostic Criteria and Severity Rating Scale, which are internationally recognized tools for diagnosis and quantification of symptom severity.

Pain intensity and foot function were measured using the Visual Analog Scale and the Foot Function Index, respectively. Emotional status was evaluated by the Hospital Anxiety and Depression Scale. Sleep quality was assessed with the Pittsburgh Sleep Quality Index, and overall quality of life was measured by the Short Form-36 Health Survey.

All assessments were performed by trained evaluators following a standardized protocol to ensure consistency across study sites. Data were collected through patient interviews, questionnaires, and clinical examinations.

The primary objective was to determine the frequency of Restless Legs Syndrome among pes planus patients compared to healthy controls. Secondary objectives included evaluating the relationship between RLS severity and pain intensity, emotional status, sleep quality, and quality of life.

This study aims to shed light on the complex interaction between biomechanical foot deformities and neurological symptoms, with the goal of informing comprehensive, multidisciplinary treatment approaches for patients with pes planus.

Inclusion Criteria:

• Age between 18 and 65 years
• Clinical diagnosis of pes planus by a physical medicine and rehabilitation specialist (for patient group)
• Ability to understand and provide written informed consent
• For control group: healthy individuals matched by age and sex without pes planus or leg pain

Exclusion Criteria:

• History of diabetes mellitus, hypothyroidism, chronic renal failure, neuropathic disorders, vasculitis, lumbar disc disease
• Previous foot fracture or surgery
• Rheumatologic diseases affecting pain perception (e.g., rheumatoid arthritis, ankylosing spondylitis, fibromyalgia)
• Significant circulatory disorders in lower extremities
• Undergoing chemotherapy or radiotherapy
• Cognitive impairment preventing questionnaire completion

This study includes adult patients aged 18-65 with clinically diagnosed pes planus and age- and sex-matched healthy controls without foot deformity or leg pain. Participants were recruited from three tertiary hospitals in Turkey and evaluated for Restless Legs Syndrome, pain, emotional status, sleep quality, and quality of life.

Individual participant data (IPD) from this study, including de-identified demographic, clinical, and questionnaire data, will be available upon reasonable request after publication of the study results. Requests should be submitted to the corresponding author, who will evaluate the request for ethical and privacy compliance before sharing

The IPD and supporting documents will be available starting from the date of publication of the study results and will remain available for at least five years.

Access to the IPD and supporting information will be granted to qualified researchers upon submission of a reasonable request explaining the research purpose. The corresponding author and ethics committee will review the requests to ensure compliance with ethical standards and protection of participant confidentiality. Data will be shared via secure data transfer methods after signing a data use agreement.