Is passive shoulder external range influenced by body posture or shoulder abduction angle?

Background: Limited passive shoulder external rotation (ER) range of motion (ROM) is one of the critical clinical criteria in the diagnosis of frozen shoulder. External rotation ROM is equally commonly assessed in sitting with the arm by the side or in supine at 90° shoulder abduction, but it is unclear if ER ROM varies with body posture or shoulder abduction angle. Using a repeated measures design the aim was to examine if there are differences in passive shoulder ER ROM when measured in different body postures and different shoulder abduction angles. Methods: Eleven healthy adults aged between 18 and 60 years were recruited. Passive shoulder ER ROM was measured bilaterally in five different positions: sitting with the arm by the side, and supine with the arm by the side and at 30°, 60° and 90° shoulder abduction. Results: There were significant increases in passive shoulder ER ROM with increasing shoulder abduction angle. No significance difference in ER ROM was found between body posture when measured with the arm by the side. Discussion: Clinicians need to be cognisant of the shoulder abduction angle at which passive ER ROM tests are performed to ensure valid interpretation regarding diagnosis and treatment effectiveness.