The Effects of Photobiomodulation on Shoulder Pain, Muscle Thickness, and Function in Subjects With Adhesive Capsulitis

Background: Adhesive capsulitis or frozen shoulder is among the most prevalent causes of pain and disability in individuals. Objectives: We aimed to evaluate the effect of Photobiomodulation (PBM) on pain, range of motion, and thickness and function of supraspinatus muscle in patients with adhesive capsulitis. Materials & Methods: Overall, 52 subjects (n=26/group) with adhesive capsulitis referring to Poorsina Hospital, physiotherapy ward, Rasht City, Iran, in 2019 participated in this study. They were randomly assigned to 2 groups of control or routine physical therapy and PBM group. The variables were pain (Visual Analogue Scale, VAS), range of motion (goniometer), the supraspinatus muscle thickness in rest and contraction, and muscle function (ultrasonography). The outcomes were examined before, after 5 and 10 sessions, and at a 1-month follow-up. Results: There were no significant differences between the two groups regarding the demographic characteristics and studied variables. The interaction of group and time (2×4) was significant for pain (P=0.02). Finally, the Bonferroni post hoc test data indicated the pain reduction in the PBM group was higher than the control group at the follow-up (P=0.03). The mixed two-factor analysis of variance indicated that the interaction of the group and time of shoulder abduction (P=0.6), shoulder external rotation (P=0.46), supraspinatus muscle thickness, rest (P=0.31), supraspinatus muscle thickness, contraction (P=0.11), and rest-contraction (P=0.66) were not significant. Conclusion: The PBM revealed greater analgesic effects than routine physical therapy in the short term and one-month follow-up. However, the effects on a range of motion and muscle thickness and function were insignificant.