Lumbar radiculopathy is a common cause of low back and leg pain, most frequently resulting from lumbar disc herniation and nerve root irritation. Conservative management, including physical therapy modalities and exercise therapy, is generally recommended as first-line treatment for patients without progressive neurological deficits. Tecar therapy (Transfer of Energy Capacitive and Resistive) is a non-invasive electrotherapeutic modality that delivers high-frequency electromagnetic energy to deep tissues and has been proposed to reduce pain, enhance microcirculation, and promote tissue recovery. However, evidence regarding its effectiveness in lumbar radiculopathy remains limited.

The aim of this randomized controlled trial is to evaluate the efficacy of Tecar therapy in patients with lumbar radiculopathy and to compare its clinical effects with conventional physical therapy and sham Tecar treatment.

A total of 90 participants with unilateral L5 and/or S1 radiculopathy will be randomized into three groups: (1) conventional physical therapy, (2) Tecar therapy combined with standard physical therapy, and (3) sham Tecar therapy combined with standard physical therapy. All participants will receive standardized postural education and a home exercise program.

The primary outcome will be pain intensity measured by the Visual Analog Scale (VAS). Secondary outcomes will include functional disability (Oswestry Disability Index), neuropathic pain characteristics (PainDETECT questionnaire), lumbar mobility (Modified-Modified Schober Test), nerve root irritability (Straight Leg Raise test), rescue analgesic consumption, and exercise adherence. Outcomes will be assessed at baseline, post-treatment (week 2), and follow-up visits at weeks 6 and 12.

This assessor-blinded, randomized controlled trial will be conducted in the Department of Physical Medicine and Rehabilitation at İzmir City Hospital, a tertiary-level outpatient center. The study will be designed and reported according to CONSORT recommendations.

Participants aged 18-65 years with clinically diagnosed unilateral L5 and/or S1 radiculopathy and symptom duration between 6 weeks and 6 months will be eligible. Diagnosis will primarily be based on clinical findings consistent with radiculopathy, including dermatomal leg pain and supportive neurological examination findings, while lumbar MRI and/or EMG will be used as confirmatory evidence. After written informed consent is obtained, eligible participants will be randomly assigned in a 1:1:1 ratio to one of three groups using computer-generated randomization with concealed allocation.

Group 1 will receive conventional physical therapy consisting of hot pack, continuous ultrasound therapy, and transcutaneous electrical nerve stimulation (TENS). Group 2 will receive Tecar therapy in addition to standardized base therapy. Tecar treatment will include capacitive and resistive energy transfer applied to the lumbar paraspinal region and gluteal muscles. Group 3 will receive sham Tecar therapy using the same procedure as the active Tecar protocol but with zero energy output. All groups will additionally receive standardized postural education and a home exercise program.

Outcome assessments will be performed by an independent physiatrist blinded to group allocation at four time points: baseline, post-treatment (week 2), and follow-up visits at weeks 6 and 12. The primary outcome will be change in pain intensity measured by the Visual Analog Scale (VAS). Secondary outcomes will include functional disability (Oswestry Disability Index), neuropathic pain features (PainDETECT questionnaire), lumbar mobility (Modified-Modified Schober Test), nerve root irritability assessed with the Straight Leg Raise test, rescue analgesic consumption, and exercise adherence.

The study aims to determine whether Tecar therapy provides additional clinical benefit over conventional physical therapy and to evaluate the effectiveness of Tecar therapy beyond placebo effects using a sham-controlled design.

Inclusion Criteria:

• Adults aged 18-65 years
• Clinical diagnosis of unilateral L5 and/or S1 lumbar radiculopathy
• Symptom duration between 6 weeks and 6 months
• Average radicular pain intensity ≥3 on the Visual Analog Scale (VAS) during the previous month
• Availability of lumbar MRI and/or EMG performed within the previous 6 months
• Willingness to participate and ability to provide written informed consent

Exclusion Criteria:

• Bilateral lumbar radiculopathy
• Lumbar spinal canal stenosis confirmed by imaging or suspected clinically (e.g., neurogenic claudication)
• Lower limb muscle strength <4/5 according to the Medical Research Council (MRC) scale
• Use of analgesic medications other than paracetamol during the study period
• Physical therapy treatment for low back or radicular pain within the past 3 months
• Contraindications to physical therapy modalities or Tecar therapy
• Previous lumbar spine surgery or interventional spinal procedures within the last 6 months
• Pregnancy, malignancy, or systemic neurological or rheumatologic disease
• Advanced spinal or lower extremity deformities (e.g., scoliosis >20°, grade 3-4 spondylolisthesis, vertebral fracture, advanced coxarthrosis)
• Inability to complete the intervention protocol or follow-up assessments

Individual participant data will not be publicly shared due to institutional data protection policies and privacy regulations. Only aggregated data will be reported in scientific publications.

Participants allocated to the Tecar therapy and sham Tecar therapy groups were blinded to treatment allocation, as both interventions used identical procedures and a hypothermic electrode head, with the sham device delivering zero energy output. Outcome assessments were performed by an independent physiatrist blinded to group allocation. Blinding of participants and therapists was not possible in the conventional physical therapy group due to the nature of the interventions. Therefore, the trial is designed as an assessor-blinded randomized controlled trial.