Frozen shoulder: hydrodilatation adds little over steroids

Adhesive capsulitis — frozen shoulder — is painful, stubborn and can drag on for months, so people are often referred for an injection before considering anything more invasive. Two options dominate conservative care: a corticosteroid injection into the glenohumeral joint, or hydrodilatation, where fluid is injected under pressure to stretch or distend the tightened capsule. Hydrodilatation is intuitively appealing because it appears to address the mechanical restriction directly. Whether that appeal is matched by better pain and function than a steroid injection, and what volume or approach works best, has never been clearly settled.

The reviewers searched PubMed, Embase and Web of Science for randomised and non-randomised trials reporting outcomes of hydrodilatation for idiopathic adhesive capsulitis. A total of 103 studies covering 9951 patients were included, and the 44 randomised trials among them were pooled in meta-analyses. Outcomes included pain on visual analogue scales, the shoulder pain and disability index (SPADI), and range of motion in external rotation, abduction and forward flexion, mainly assessed at 12 weeks. The team also catalogued technique: injected volume, imaging guidance and the approach used to enter the joint.

Against corticosteroid injection alone at 12 weeks, hydrodilatation produced greater external rotation (SMD 0.61, 95% CI 0.14 to 1.08) but with high heterogeneity (I2 81.6%) and low certainty, and no significant differences in pain VAS, SPADI, abduction or forward flexion. Added to physical therapy or exercise, it gave slightly better pain VAS (SMD 0.288, 95% CI 0.01 to 0.57, low certainty) and SPADI (SMD 0.52, 95% CI 0.08 to 0.96, very low certainty) than therapy alone, with no extra range-of-motion gains. Technique was highly variable: mean injected volume 36.0±26.3 mL, median 28 mL, range 8.3-200. Infection was rare, reported in 0.02% — two cases among 8754 patients.

This is the largest synthesis of the question so far, and it lands against the enthusiasm for hydrodilatation as a mechanical fix. The one statistically favourable range-of-motion result was inconsistent across studies and did not carry through to how patients rated their pain or function, which is what actually matters to them. Because the pooled trials used volumes spanning an enormous range and different guidance methods and entry points, the analysis cannot tell whether a better-standardised technique would perform differently. Ideal volume, the state of the capsule and how many injections to give all remain unresolved.

If you have frozen shoulder and are weighing options, this is a reason to think hydrodilatation is not clearly superior to a corticosteroid injection, nor a reliably valuable add-on to physiotherapy, on current evidence. The gains that did appear were small, of low certainty and mostly in a single movement direction rather than in pain or day-to-day function. Reassuringly, serious complications such as infection appear very uncommon. The wide variation in how the procedure is performed is itself worth knowing about, because it means results at one clinic may not describe what happens at another.