Low-energy laser therapy application on knee joints as an auxiliary treatment in patients with polyarticular juvenile idiopathic arthritis: a dual-arm randomized clinical trial

Patients with juvenile idiopathic arthritis (JIA) always experience persistent pain and stiffness which induces muscle weakness, fatigue, and functional limitations. This study evaluated whether applying low-energy laser therapy (LLT) on the knee joint could be an effective adjuvant intervention for patients with JIA. Sixty children with polyarticular JIA participated and were randomly allocated to receive either LLT (wavelength λ = 903 nm; power output of 50 mW; and energy of 1.5 J) plus exercises (LLT group) or exercises alone (control group). Pain, peak concentric torque of quadriceps muscles, fatigue, and functional status were measured by the visual analogue scale, isokinetic testing system, Pediatric Quality of Life Inventory Multidimensional Fatigue Scale, and Childhood Health Assessment Questionnaire, respectively pre- and post-intervention, and at 6-month follow-up. Per the mixed-model analysis of variance, the LLT group showed a statistically more favorable improvement in pain (P = .003, η_p² = .014), fatigue perception (P = .004, η_p² = .015), and functional status (P = .022, η_p² = .09) across the three assessment occasions, as compared to the control group. However, no significant difference was demonstrated between both groups concerning peak concentric torque (all P > .05). Incorporation of LLT into the standard physical rehabilitation program for patients with JIA has the potential to induce more conducive improvements in pain, fatigue, and functional performance, but is not effective for improving muscle performance.