Sixty-six patients with subacromial impingement syndrome were randomized to receive either high-intensity laser therapy (HILT) plus physical therapy (n=33) or sham laser plus physical therapy (n=33). The primary outcome was supraspinatus tendon elasticity measured with shear wave elastography. Secondary outcomes included pain (VAS) and function (SPADI). Outcomes were assessed at baseline and after two weeks of treatment. Overall, the results of the study revealed no changes in tendon elasticity in either group, while both groups had statistically and clinically significant improvements in pain and function. Although HILT plus physical therapy was statistically superior to physical therapy alone for pain and SPADI, the between-group differences did not reach clinical significance. These findings suggest that adding HILT improves symptoms modestly but does not alter tendon mechanical properties in the short term.