The diabetes-frozen shoulder link is biochemical, not coincidental
Persistently high blood glucose causes glucose molecules to bind to collagen fibres in a process called glycation. The shoulder joint capsule is dense with collagen, and once that tissue thickens and contracts, the result is adhesive capsulitis, the clinical name for frozen shoulder. A 2019 study published in the Journal of Shoulder and Elbow Surgery found that diabetics develop frozen shoulder at roughly four to five times the rate of non-diabetics, and their recovery takes significantly longer. The mechanism is not mysterious: poor glucose control accelerates collagen cross-linking, and the shoulder capsule pays the price before most other joints because of its particular tissue composition.
