INTRODUCTION: The aim of this study was to establish whether diabetes mellitus (DM) affects the prognosis for patients with a frozen shoulder.

METHODS: In this prospective two-year follow-up study, we included 235 patients with newly diagnosed unilateral frozen shoulder. Among the 235 patients, 34 (14%) were diagnosed with DM prior to their inclusion in the study. Patients were asked to fill out a questionnaire at the time of diagnosis and at six-, 12- and 24-month follow-ups. The questionnaire included the Oxford Shoulder Score (OSS) and a visual analogue scale (VAS) for both maximum and average daily pain. DM status was recorded for all patients and glycated haemoglobin was measured for patients not diagnosed with DM.

RESULTS: Overall, patients with and without DM had a similar OSS (p = 0.22) and VAS score for maximum (p = 0.46) and average (p = 0.46) daily pain at the time of diagnosis compared with patients without DM. Both groups improved their OSS and VAS score, but patients with DM had a poorer OSS at the six-month (p = 0.04) and 24-month follow-ups (p = 0.02); poorer VAS scores for maximum daily pain at the six-month (p = 0.04), 12-month (p = 0.03) and 24-month follow-ups (p = 0.03); and poorer VAS scores for average daily pain at the six-month (p = 0.02) and 12-month follow-ups (p = 0.01).

CONCLUSIONS: This study shows that patients with frozen shoulder may expect a gradual improvement of both pain and movement during a two-year follow-up, but also that having DM is associated with a poorer prognosis.

FUNDING: none.

TRIAL REGISTRATION: NCT01978886.