Objective: Performing repetitive overhead movements puts stress on the shoulder joint, leading to uneven shoulders and pain in the shoulder joint. The purpose of this study was to evaluate and compare the strength and Range of Motion (ROM) of internal and external rotator muscles in volleyball players with and without uneven shoulders.
Methods: This is a descriptive and causal-comparative study conducted on 30 volleyball players randomly assigned into two groups of patients with uneven shoulders and healthy peers. A dynamometer (Manual muscle testing) was used to measure the strength of the rotator muscles at zero degrees,  a goniometer to measure the ROM of muscles, and a scoliometer device to measure the symmetry of shoulders.
Results: There was a significant difference in the strength of internal (P=0.03) and external (P=0.02) rotator muscles between groups with and without uneven shoulders. The ROM of internal (P=0.02) and external (P=0.03) rotator muscles were also significantly different between the two groups.
Conclusion: High muscle strength in volleyball players with uneven shoulders is a risk factor. Limitations in the ROM of rotator muscles in the shoulder joint of these athletes showed the need for more attention to preventive approaches by creating corrective strategies.