Discussion
OA, weakness of the knee flexor, impingement, pain, OA knee, metabolic activityKnee pain
OA KNEE
Laser therapy has been broadly used as a physical modality in clinical rehabilitationReductions in knee strength and cross-sectional areas have been well documented in OA patients. The weakness of the knee flexor and extensor contributes to poor dynamic stability and knee controlThe results showed that the use of the 808 nm wavelength led to superior beneficial effects in terms of increasing knee extensor strength as compared to the 660 nm wavelength and the sham control. Also, the 660 nm wavelength did not show therapeutic effects on muscle strength. The differences in physiological and therapeutic effects can be explained in terms of the relationship between photon impingement and biological tissues. When photons hit biological tissue, their onward transportation depends on the reflectance, scattering, and absorption effects of the materials. Hence, various wavelengths lead to different absorption abilities. The spectrum of the 808 nm wavelength was in the infrared fields and the 660 nm wavelength is in the red fields. It is well established that cytochrome C oxidase, the terminal enzyme of the respiratory chain in mitochondria, and proteins in the cytoplasmic membrane both absorb light in the red and infrared sections of the electromagnetic spectrum respectively. They produce similar biological effects but lead to distinct metabolic activityKnee pain causes difficulty in daily functional activities for knee OA patients. The adaptive mechanism during walking with an OA knee is characterized by decreased stride length, increased walking base of support, and increased time required for the double support phase in order to avoid pain provocationSit-to-stand, stair climbing, and TUG tests require greater knee extensor strength, knee joint range of motion, and joint moment than walking. The LLLT intervention groups showed an increased score for the 30-s sit-to-stand and decreased the time required for stair climbing and the TUG. The testing time among the three groups presented the same normative scores for the 30-s chair stand testInterestingly, the sham control group revealed the placebo responses in the functional test through a reduction in walking time, the TUG test, and stair climbing. We assumed that there was significance in the genuine biopsychosocial phenomena when the patients received the placebo effects from the laser treatment. Clinical placebo effects can be explained in terms of release of neurotransmitters and activation in many areas of the brain, which are complex neurobiological mechanisms in the connection between the brain and the bodySome limitations should be addressed in this study. Firstly, as the previous study mentioned the required number of each intervention group to detect the significant therapeutic effects (N = 30)