Seventy-two patients with displaced intracapsular proximal humeral fractures were randomized to receive internal fixation and open reduction in combination with intraoperative glenohumeral joint lavage (n=36) or without lavage (n=36). Primary outcomes of interests included shoulder range of motion (ROM; internal fixation, external rotation, forward flexion, and abduction) and Constant Score at 6 weeks and 3, 6, and 12 months follow-up. Results of this study revealed no statistically significant differences between the 2 groups for the Constant score, forward flexion, and abduction at all timepoints (p>0.05 for all). Yet, external rotation and internal rotation were statistically significantly higher in the no lavage group compared to the lavage group at 3 months follow-up (p=0.023, p=0.042; respectively). The incidence of complications did not statistically significantly different between the 2 groups (p=0.321).