Frozen shoulder, also known as adhesive capsulitis, is caused by inflammation and thickening of the shoulder joint capsule, leading to stiffness, pain, and restricted movement. It can be primary (idiopathic) with unknown cause but often linked to systemic conditions like diabetes and thyroid disorders. Secondary frozen shoulder occurs after shoulder injury, surgery, prolonged immobilization, or conditions that keep the shoulder still for long periods. Risk factors include diabetes, thyroid problems, heart disease, stroke, and others. The exact cause of the inflammation and capsule tightening remains partially unknown, but it involves fibrosis and adhesions within the shoulder joint capsule.
