Comparison of the Effect of High-Intensity Laser Therapy and Quadriceps Muscle Strengthening Exercises Using Biofeedback on Pain, Stiffness and Function of Patients with Knee Osteoarthritis: A Randomized Clinical Trial.

Objectives: This study aims to compare the effects of high-intensity laser therapy (HILT) and quadriceps muscle strengthening exercises using biofeedback on pain and function in patients with knee osteoarthritis (KOA). Methods: This randomized, two-group clinical trial included patients with KOA (grades II - III of the Lawrence Kellgren classification) who met the inclusion criteria. Written informed consent was obtained from participants before they were randomly allocated into one of two groups: HILT + therapeutic exercise (group A) or quadriceps muscle strengthening exercises using biofeedback + therapeutic exercise (group B). Both groups followed the same therapeutic exercise regimen during the study.Knee pain severity was evaluated using the Visual Analogue Scale (VAS), and functional disability was assessed with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire before the intervention.For group A, HILT was performed using a BTL-6000 HIL device (wavelength 1064 nm, maximum power 12 W) following the manufacturer-recommended protocol. A pain relief program (10 W, 120 J/cm²) was administered for 120 seconds per session over ten sessions. Treatment protocol, laser positioning, and session duration were standardized. Two follow-up assessments (immediately and one-month post-intervention) were conducted to evaluate outcomes based on the VAS and WOMAC scores. Results: The study included 40 participants with KOA, divided evenly between the two groups (20 in each). The average age of the participants was 59.34 ± 6.92 years. High-intensity laser therapy group (group A): Visual analogue scale pain scores decreased significantly immediately after and one month post-intervention compared to baseline (P < 0.01). However, the VAS score one month after the intervention showed no significant difference compared to the immediate post-intervention score (P = 0.59). Biofeedback group (group B): VAS pain scores also decreased significantly both immediately after and one month post-intervention compared to baseline (P < 0.05). The difference in VAS pain reduction between the two groups was significant, with the HILT group showing greater improvement immediately after the intervention and one month later (P = 0.007). Conclusions: The study findings suggest that both quadriceps muscle strengthening exercises using biofeedback and HILT effectively reduce pain in KOA patients. However, HILT demonstrated superior efficacy compared to biofeedback exercises. These results support the use of HILT as a noninvasive therapeutic modality for KOA, particularly for patients with a higher risk of surgery due to preexisting comorbidities.