Frozen shoulder — adhesive capsulitis — is a condition that most clinicians recognize and most patients endure, but that is less well understood biologically than its prevalence warrants. It affects approximately 2–5% of the general population, with a significant skew toward the fifth and sixth decades, toward women, and toward patients with diabetes — in whom the incidence is three to five times higher than the general population. It is predominantly a condition of the shoulder's joint capsule, which undergoes a fibroproliferative process producing progressive contracture, pain, and loss of motion in a predictable pattern.
The Biology
Histologically, frozen shoulder looks like a scar — the shoulder joint capsule, normally a thin and compliant structure, becomes thickened, contracted, and infiltrated with myofibroblasts and inflammatory cells producing excess type I and III collagen. The rotator interval — the region of capsule between the supraspinatus and subscapularis tendons — is the most consistently involved area. The inferior glenohumeral ligament, which normally allows the arm to elevate fully, becomes contracted and limits elevation. The anterior capsule contracts and limits external rotation. The result is a shoulder that is globally restricted in all directions of motion.
Insidious onset of shoulder pain that is often severe at night and with any motion at end range. Motion is still present but is accompanied by significant pain. The inflammatory process is active. This is the phase where targeted intervention — specifically corticosteroid injection — has its strongest evidence base for short-term pain relief.
Pain begins to diminish, but motion loss is at its maximum. The fibroproliferative process has produced a contracted capsule that mechanically limits movement in all directions. Activities of daily living — reaching behind the back, sleeping, overhead activity — are significantly limited. This phase is often when patients present for evaluation.
Motion gradually returns. In most patients, near-complete or complete resolution occurs — but "most" is not "all," and the timeline is long. Approximately 15–20% of patients have persistent motion limitations or symptoms beyond two years. Diabetic patients have a more prolonged course and higher rate of incomplete recovery.
What the Evidence Says About Treatment
The natural history of frozen shoulder is favorable for most patients — which has historically been used to justify a "wait and see" approach. But the timeline of untreated adhesive capsulitis is measured in years, and the functional limitations during that period are substantial. The evidence supports active intervention across multiple phases.
Corticosteroid injection: Most effective in the freezing phase, when the inflammatory component is dominant. A single glenohumeral joint injection (not subacromial — different target) provides significant short-term pain relief and accelerates the return of motion compared to placebo in randomized trials. Effect wanes at 3–6 months; a second injection is reasonable if motion gains plateau. The combination of injection plus supervised physical therapy consistently outperforms either alone.
Physical therapy: Gentle range-of-motion and stretching in the pain-free range. Aggressive passive stretching in the freezing phase amplifies inflammation and worsens outcomes — a common and consequential error. The program should begin with pendulum exercises and gentle Codman mobilizations and progress to active-assisted range of motion as the phase evolves toward thawing.
Hydrodilatation: Ultrasound-guided injection of saline plus steroid into the glenohumeral joint, distending the contracted capsule. A reasonable next step for patients who have not responded adequately to standard injection and therapy. Evidence supports meaningful motion gains beyond steroid injection alone.
Manipulation under anesthesia / arthroscopic capsular release: Reserved for patients with prolonged frozen phase who have failed all conservative measures, typically after 12–18 months. Arthroscopic release directly addresses the contracted capsule and produces reliable motion restoration, with low complication rates in experienced hands.
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