Photobiomodulation as a Preconditioning Modality to Enhance Physical Therapy Outcomes in Musculoskeletal Pain

Abstract

Background: Musculoskeletal (MSK) pain remains a leading cause of global disability. Photobiomodulation (PBM) is a non-thermal, non-ionizing light therapy that modulates mitochondrial cytochrome c oxidase (CCO), promoting ATP synthesis, nitric oxide (NO) release, and downstream anti-inflammatory signaling. This practice-based evaluation examined whether a five-minute multi-wavelength LED PBM protocol applied immediately before physical therapy (PT) sessions could reduce pain and improve functional tolerance in MSK patients.

Methods: Twenty-five consecutive adults undergoing PT for chronic or subacute MSK pain received multi-wavelength LED PBM (635, 670, 810, and 850 nm; irradiance ~90 mW/cm² at 6 inches; approximately 27 J/cm² fluence per session) applied immediately before each PT session. Numeric pain rating scale (NPRS, 0–10) scores were recorded before PBM and after the combined PBM-PT session. A responder was defined as achieving ≥50% pain reduction.

Results: Mean baseline pain score was 5.6 ± 1.8; post-session score was 2.3 ± 1.2 (mean reduction 3.3 points; 59% reduction; p < 0.001). Eighty percent of patients met the ≥50% responder threshold; 13% reported complete resolution. No adverse events were recorded.

Conclusions: A five-minute PBM preconditioning protocol applied before PT produced clinically meaningful, acute reductions in pain and improved functional readiness in MSK patients. These practice-based findings support further controlled investigation of pre-session PBM as a rehabilitation adjunct.

Introduction

Musculoskeletal conditions account for approximately 1.71 billion cases of chronic disability worldwide and are among the most frequent presenting complaints in outpatient rehabilitation settings. Conventional management—including analgesics, corticosteroid injections, and surgical referral—carries limitations in long-term efficacy, tolerability, and patient adherence. Physical therapy (PT) addresses the functional and biomechanical dimensions of MSK pain but is frequently limited by patient pain levels that reduce participation intensity and therapeutic progress.

Photobiomodulation (PBM), also referred to as low-level laser therapy (LLLT) or photobiomodulation therapy (PBMT), is a non-thermal, non-ionizing optical intervention that uses red and near-infrared (NIR) wavelengths to modulate cellular metabolism. The primary chromophore is cytochrome c oxidase (CCO), the terminal enzyme of the mitochondrial electron transport chain. Photon absorption by CCO dissociates inhibitory nitric oxide (NO), restoring electron transport, increasing ATP synthesis, and triggering downstream anti-inflammatory and analgesic signaling cascades.

Despite a growing body of evidence supporting PBM for acute and chronic MSK pain, its use as a preconditioning modality—applied immediately before PT to optimize session readiness—remains undercharacterized in the literature. This practice-based evaluation was designed to assess whether a brief, standardized PBM protocol applied before PT sessions could produce clinically meaningful reductions in acute pain and improve functional performance during the session.

Methods

Study Design and Setting: This was a prospective, single-arm, practice-based evaluation conducted in an outpatient physical therapy clinic. The evaluation was conducted under standard clinical care conditions without randomization or blinding. All patients provided verbal informed consent for the use of PBM as a clinical adjunct.

Participants: Twenty-five consecutive adult patients (≥18 years) presenting with chronic or subacute MSK pain of the spine, shoulder, knee, hip, or extremities were enrolled. Patients were included if they had a baseline NPRS score of ≥3 and were initiating or continuing a course of outpatient PT. Patients with active skin lesions over the treatment area, photosensitizing medications, or known photosensitivity disorders were excluded.

Intervention: The PBM device used was a multi-wavelength LED panel delivering wavelengths of 635 nm, 670 nm, 810 nm, and 850 nm with a combined irradiance of approximately 90 mW/cm² at 6 inches. Each session consisted of a five-minute application to the primary pain region, delivering approximately 27 J/cm² per session. PBM was applied immediately before the standard PT session by the treating physical therapist.

Outcome Measures: The primary outcome was change in pain intensity as measured by the Numeric Pain Rating Scale (NPRS, 0–10). NPRS was recorded immediately before PBM application and immediately after completion of the combined PBM-PT session. The secondary outcome was therapist-observed change in functional performance and range of motion (ROM) during the PT session, documented as a categorical assessment (improved / unchanged / worsened). A clinically meaningful responder was defined as achieving ≥50% reduction in NPRS score from pre-session baseline.

Statistical Analysis: Baseline and post-session NPRS values were compared using a two-tailed paired t-test. Results are reported as mean ± standard deviation. Statistical significance was set at p < 0.05. Responder rates were calculated as the proportion of patients meeting the ≥50% NPRS reduction threshold.

Results

Pain Score Outcomes: Mean baseline NPRS was 5.6 ± 1.8; mean post-session NPRS was 2.3 ± 1.2 (absolute reduction: 3.3 points; 59% reduction from baseline; p < 0.001). The distribution of improvement by category was: <25% improvement, 4% of patients; 25–49% improvement, 35%; 50–74% improvement, 48%; 75–99% improvement, 0%; complete resolution (100%), 13%. Responder rate (≥50% reduction) was 80% as reported by treating clinicians. No patients reported worsening of pain following the session.

Functional Outcomes: Therapist-observed functional performance improved in 22 of 25 patients (88%), was unchanged in 3 patients (12%), and worsened in 0 patients. ROM improvements were noted most consistently in shoulder and knee presentations. Patients subjectively reported improved mobility, reduced stiffness, and greater exercise tolerance during the PT session.

Discussion

Principal Findings: This practice-based evaluation demonstrates that a five-minute, multi-wavelength LED PBM protocol applied immediately before PT produces clinically meaningful acute reductions in pain across a diverse MSK patient population. The 59% mean reduction in NPRS from baseline and the high responder rate are consistent with controlled trials of PBM for MSK pain, and extend the evidence base to the specific preconditioning application—a distinct and undercharacterized protocol context.

Mechanistic Rationale for Preconditioning: The observed analgesic response is consistent with the established photobiological mechanisms of PBM. Photon absorption by CCO dissociates inhibitory NO from the enzyme, restoring mitochondrial electron transport and increasing ATP synthesis. Released NO induces local vasodilation, improving microcircular perfusion and oxygen delivery to metabolically compromised tissue—effects that directly counter the local acidosis and ischemia that amplify pain-signal transduction. Anti-inflammatory gene expression changes, including downregulation of NF-κB and pro-inflammatory cytokines, have been documented within 30–60 minutes of PBM exposure, providing a mechanistic basis for the rapid analgesic onset observed in this preconditioning context.

Clinical Implications: If confirmed in controlled trials, the preconditioning model offers a practical, low-burden addition to PT workflow. A five-minute device application requires minimal staff time, involves no adverse effects at the doses studied, and could reduce the pain-related barriers to productive PT participation that frequently limit session intensity and therapeutic progress.

Conclusions

A five-minute multi-wavelength LED PBM protocol applied immediately before physical therapy sessions produced a 59% mean reduction in acute pain scores and an 88% rate of therapist-observed functional improvement in 25 consecutive MSK patients, with no adverse events. These practice-based findings provide a preliminary clinical signal supporting pre-session PBM as a potentially meaningful rehabilitation adjunct. The preconditioning mechanism—transient CCO activation, NO release, vasodilation, and peripheral sensitization reduction—offers a biologically coherent rationale for this acute response. Controlled, prospective investigation is warranted to establish efficacy, optimal dosimetry, and durability of effect.