Effects of hyperbaric oxygen therapy on recovery acceleration in Japanese professional or semi-professional rugby players with grade 2 medial collateral ligament injury of the knee: A comparative non-randomized study

Introduction: The effects of hyperbaric oxygen (HBO2) therapy on sprains, ligament injuries, and muscle strains have been reported in several animal studies. In a dog model of compartment syndrome and in a rat contused skeletal muscle injury model, the significant effects of HBO2 therapy on the reduction of edema and muscle necrosis have been reported. In basic research HBO2 therapy stimulated fibroblast activity to improve the healing process. Because of this it expected that HBO2 therapy might improve focal edema and pain in the acute phase and accelerate the healing of injured tissues in athletes with a medial collateral ligament (MCL) injury of the knee. This study aimed to examine the short-term effects of HBO2 application subjectively, and the long-term effects of HBO2 therapy in Japanese professional or semi-professional rugby players with grade 2 MCL injury of the knee. Methods: Thirty-two professional or semi-professional rugby players with grade 2 MCL injury of the knee were investigated. First, in the HBO2 group (n=16), HBO2 therapy was performed during the acute phase. Visual analog scales (VASs) immediately before and after HBO2 therapy on the same day were compared. Next, we retrospectively evaluated the time to return to play in the HBO2 (n=16) and non-HBO2 (n=16) groups. Results: VAS scores for pain while walking immediately before and after HBO2 therapy on the same day were 37.4 Å} 20.1 (mean Å} standard deviation) and 32.4 Å} 21.8, respectively (p<0.001). The VAS scores for pain while jogging were 50.7 Å} 25.6 and 43.9 Å} 25.0, respectively (p<0.001). The time to return to play was 31.4 Å} 12.2 days in the HBO2 group and 42.1 Å} 15.8 days in the non-HBO2 group, indicating a significant difference between the groups (p<0.05). Conclusion: HBO2 therapy may reduce pain and accelerate the return to play in athletes with grade 2 MCL injury of the knee in this non-randomized study.