Effect of Low-Level Laser Therapy (LLLT) on viscoelasticity of the contracted knee joint: Comparison with whirlpool treatment in rats

Background and Objective: The purpose of this study was to compare the effect of Low-Level Laser Therapy (LLLT) with sham and whirlpool treatment on the contracted knee joint in rat. Study Design/Materials and Methods: Forty-eight Wistar rats were operated on to immobilize knee joint, and 1 week after operation they were randomly assigned to four treatment groups: laser 40 mW (3.9 W/cm(2)), laser 60 mW (5.8 W/cm(2)), whirlpool (42 degrees C), and sham laser. Tunable Ga-AZ-As semiconductor (810 nm) laser was used for another 2 weeks of treatment. Removing and preparing bilateral hind legs, degree of knee contracture was assessed by measuring the knee flexion angle, weight of the gastrocnemius muscle, and periarticular connective tissue viscoelasticity measuring phase-lag and stiffness. Results and Conclusion: Laser irradiation showed no significant changes except the phase-lag of laser 60 mW. Under the conditions of this study, LLLT stimulation did not provide a significant effect for minimizing the degree of experimental joint contracture over whirlpool treatment. (C) 1998 Wiley-Liss, Inc.