Diabetes as a Prognostic Factor in Frozen Shoulder: A Systematic Review.

Most included studies were judged to be at high risk of bias, and 21 of the 28 studies were rated high, so the findings are not firm. The studies varied widely in outcome measures and follow-up length, so the reviewers could not combine them into one pooled estimate. Few studies adjusted for confounders or compared baseline characteristics between groups, and diabetes was often poorly defined or its type was not reported. For range of motion, 3 of 13 studies suggested better motion in people with diabetes, so that domain was inconsistent. For pain, differences often did not reach the studies' significance threshold, and the association appeared small. Many participants had received secondary care treatments such as release, manipulation, or injection, so it is unclear whether the same prognosis applies to people managed in primary care with pain relief, mobilization, and exercise. The evidence grading used reviewer judgment and counting of significant results, which is less transparent than combining all studies statistically.

Do not conclude that diabetes itself caused worse frozen shoulder recovery. The review shows an association in observational cohorts, and participants received many different treatments, so the contribution of any single treatment cannot be separated.