Ko YW, Park JH, Youn SM, et al. - This study was undertaken to investigate how comorbidities influence the recovery speed and clinical outcomes after manipulation under anesthesia (MUA). Researchers recruited 281 consecutive primary stiff shoulders in the frozen phase treated with MUA were included in this study between April 2013 and September 2018. They evaluated the comorbidities of individuals and classified them into the control (n=203), diabetes mellitus (DM) (n=32), hyperlipidemia (n=26), and thyroid disorder (n=20) groups. For primary stiff shoulder, the range of motion recovery speed and responsiveness to MUA were poorer for the DM and thyroid disorder groups than for the control group. Outcomes were poorer when the comorbidity was DM, particularly, in comparison with any other disease. Whether individuals have comorbidities, then they should be informed before MUA that the comorbidity could affect the outcomes of treatment.