Introduction To study if Diabetes Mellitus (DM) affects the severity of a frozen shoulder prognosis.

Methods In this 2 year follow-up study patients from three participating hospitals with newly diagnosed frozen shoulder were consecutively included and asked to fill out a questionnaire: at time of diagnosis and at 6-, 12- and 24 months follow-up. The questionnaire included the Oxford Shoulder Score (OSS) and the Visual Analogue Scale (VAS) for both maximum and average daily pain. Furthermore, patients were asked to report on whether arthroscopic release had been performed. DM status was recorded for all patients, and patients not previously diagnosed with DM were invited to be tested with the HbA1c test.

Results A total of 235 patients were included, of which 34 were previously diagnosed with frozen shoulder. Patients with DM had similar OSS (p=0.22) and VAS score for maximum (p=0.46) and average (p=0.46) daily pain at time of diagnosis compared to patients without DM. Both groups improved in OSS and VAS score, but patients with DM had a worse OSS at 6 month (p=0.04), and 24 months follow-up (p=0.02); worse VAS score for maximum daily pain at 6 month (p=0.04), 12 month (p=0.03) and 24 months follow-up (p=0.03); and worse VAS score for average daily pain at 6 months (p=0.02), and 12 months follow-up (p=0.01)

Patients with DM had an increased probability of undergoing arthroscopic release (p<0.05).

Conclusion Patients with DM have a worse prognosis of their frozen shoulder, but all patients can expect gradually improvement during the 2 years following their diagnosis.