Frozen Shoulder: What the World’s Largest Clinical Trial Reveals About Surgery vs. Therapy

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For those living with "frozen shoulder"—medically known as adhesive capsulitis—the world shrinks to the radius of a locked joint. It begins with an insidious onset of deep-seated pain that gradually hardens into a debilitating "gridlock." Simple gestures become Herculean tasks: reaching for a seatbelt, pulling on a coat, or finding a sleeping position that doesn't trigger a jolt of agony. In this state of inflammation and scarring, the shoulder joint contracts, leaving patients desperate for a solution that will restore their range of motion.

To settle the debate over which intervention truly works, the UK FROST study was launched. As a multicentre, pragmatic, three-arm, superiority randomised clinical trial—the largest of its kind—it put the three most common secondary care treatments to the ultimate test. The study aimed to determine whether expensive, invasive surgery is actually superior to a structured physiotherapy pathway.

The Superiority Myth: All Roads Lead to Recovery

The most striking revelation from the UK FROST study was that at the 12-month mark, no single treatment proved "clinically superior." To measure success, researchers used the Oxford Shoulder Score (OSS), a 48-point scale where higher scores indicate better function and less pain.

The trial was designed with a "target difference" of 4 to 5 points—the minimum improvement a patient would actually notice in their daily life. While the results showed that patients who underwent Arthroscopic Capsular Release (ACR) had statistically better scores than those in the physiotherapy group (a difference of 3.06 points, p=0.011), the gap failed to reach that critical 5-point clinical threshold.

In the language of evidence-based medicine, this is a vital distinction: the surgical advantage was "statistically significant" (meaning it likely wasn't due to chance), but it wasn't "clinically significant" (meaning the patient wouldn't feel a meaningful difference between the two). As the study authors concluded: "none of the three interventions were clinically superior." Whether the patient chose the scalpel or the exercise mat, the 12-month outcome was remarkably similar.

The Cost of Invasive Action: Safety and the Surgical Scalpel

While clinical outcomes were nearly identical at one year, the journey to get there varied significantly in terms of risk. The trial evaluated three distinct pathways:

1. Early Structured Physiotherapy: A specifically designed program of 12 sessions including mobilization and home exercises, initiated by a steroid injection.
2. Manipulation Under Anaesthesia (MUA): A procedure where a surgeon stretches and tears the scarred capsule while the patient is unconscious, followed by a steroid injection and postprocedural physiotherapy.
3. Arthroscopic Capsular Release (ACR): A more invasive surgery to divide the contracted capsule, often followed by manipulation and always by postprocedural physiotherapy.

The safety data was telling. ACR carried the highest risk profile, with eight serious adverse events reported, including one patient suffering a stroke and others experiencing deep vein thrombosis or surgical site infections. In contrast, MUA saw only two serious events, and the early structured physiotherapy group saw zero. This suggests that while ACR is a powerful tool, its higher complication rate makes it a "selective" option rather than a default first-line treatment.

The Waiting Game: Why Access is Therapy

For a patient whose life is on hold, the most important metric isn't just how they recover, but how fast they can start. The UK FROST study revealed a massive disparity in access. The median wait time for physiotherapy was just 14 days. For MUA, it was 57 days, and for ACR, it stretched to 72 days.

This delay has real-world consequences. At the 3-month follow-up, the ACR group actually reported worse outcomes than the other two groups. This "surgical lag" occurred because many ACR patients were either still on the waiting list or were in the early, painful stages of post-operative recovery while the physiotherapy group had already completed their treatment. When you are unable to sleep or work, a two-month head start on recovery is a significant clinical advantage.

Efficiency in the Theatre: The Economic Winner

From a healthcare system perspective, the UK FROST study provides a clear economic winner: Manipulation Under Anaesthesia (MUA). The researchers used Quality-Adjusted Life-Years (QALYs)—a metric where one unit represents one year of perfect health—to determine value for money.

At the standard NHS threshold of £20,000 per QALY, MUA had an 86% probability of being the most cost-effective treatment. ACR, by comparison, was substantially more expensive—costing roughly £1,733 more per patient than physiotherapy—without providing a commensurate leap in health quality. In a system where hospital beds and operating theatre time are precious resources, MUA offers the most efficient balance of cost and clinical improvement.

The Reality of Persistence

There is a final, sobering takeaway for both clinicians and patients. While the treatments in this trial were highly successful—most participants reached nearly full function with a median score of 43 out of 48—frozen shoulder remains a stubborn adversary.

Historical data on the general population suggests that around 40% of patients may still report some persistent symptoms even four years after the initial onset. While the UK FROST participants generally fared better, the "slow or incomplete" nature of recovery in the broader population serves as a reminder that this condition is a marathon, not a sprint.

There is, however, a notable trade-off regarding further intervention. While the physiotherapy pathway is safer and faster to access, 15% of those patients eventually required further treatment (such as surgery) compared to only 4% of those who started with ACR.

A Blueprint for Future Shoulder Care

The UK FROST study has effectively redrawn the map for adhesive capsulitis treatment. It proves that more invasive does not necessarily mean better.

For the patient in the consultation room, the "Early Structured Physiotherapy" pathway—the combination of a steroid injection followed by expert-led exercise—should be a primary consideration. It is fast, safe, and at 12 months, delivers results that are nearly indistinguishable from surgery. MUA stands as the most cost-effective hospital intervention, while ACR is best reserved for complex cases or when less invasive methods have failed.

Ultimately, the study empowers the patient. If the long-term outcomes are virtually the same, would you choose the surgical theater and the risks that come with it, or would you choose the injection and the exercise mat? The evidence suggests that for most, the less invasive path is just as effective.

​REF: ​

• Management of adults with primary frozen shoulder in secondary care (UK FROST): a multicentre, pragmatic, three-arm, superiority randomised clinical trial​