Laser therapeutic applications, such as the use of high energy lasers (HILT), are widely used in physical therapy, but basic studies on the mechanisms of action of HILT on tendinous/ligamentous tissue are largely lacking. The aim of this study was to investigate microcirculatory changes of the patellar tendon by HILT. 21 healthy volunteers were treated with HILT. Before and after the intervention, as well as 10 minutes later, the microcirculation was measured by noninvasive laser spectroscopy (O2C device). Tissue temperature was recorded at the measurement time points using thermography. Blood flow increased significantly by 86.38 AU (p < 0.001) after the intervention and by 25.76 AU (p < 0.001) at follow-up. Oxygen saturation increased by 20.14% (p < 0.001) and 13.48%, respectively (p < 0.001), whereas relative hemoglobin decreased by 6.67 AU and 7.90 AU, respectively. Tendon temperature increased by 9.45° and 1.94° Celsius, respectively. Acceleration of blood flow by improving the flow properties of erythrocytes and platelets may have caused the results.

UR and CL are members of the Zimmer GmbH scientific team whose OptonPro laser was used for the study intervention.

The study protocol was prospectively registered with the German Clinical Trials Register (DRKS00028155).

The authors received no specific funding for this work.

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The study has been reviewed and approved by the ethical committee of the DIPLOMA Hochschule, Germany (Nr. 1021/2021), has been carried out in accordance with the declaration of Helsinki and has obtained written informed consent from the participants .

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