What is frozen shoulder?

Frozen shoulder, properly called adhesive capsulitis, is an inflammatory thickening and contracture of the shoulder capsule — the connective-tissue sleeve around the ball-and-socket joint. The capsule, which is normally elastic, becomes inflamed and then progressively scarred and shortened. The shoulder loses range in every direction, especially external rotation. The condition is self-limiting but typically lasts 18 to 24 months from onset to full resolution, and the pain in the early phase can be severe.

In most patients there is no identifiable trigger — this is called primary or idiopathic frozen shoulder. It is more common in people aged 40–60, in women, and in patients with diabetes (in whom it tends to be more resistant to treatment). Secondary frozen shoulder follows an episode of immobilisation, a rotator cuff injury, a shoulder operation, or a fracture of the proximal humerus or clavicle.

Does it really go away on its own?

In most cases yes, but the timeline is long. The natural history is three phases: a painful 'freezing' phase of 2–9 months, a stiff 'frozen' phase of 4–12 months, and a 'thawing' phase of 6–24 months as range gradually returns. The total course typically runs 18 to 24 months. A small minority of patients have residual stiffness that does not fully resolve.

When does an injection help?

An ultrasound-guided intra-articular corticosteroid injection is the single most evidence-supported intervention in the early painful phase, and is recommended in clinical guidelines including the UK FROST trial protocol. It does not shorten the total course of the condition but it meaningfully reduces pain during the freezing phase and is often the difference between sleeping at night and not.

What is hydrodilatation?

Hydrodilatation is an image-guided procedure in which a larger volume of fluid — typically saline mixed with local anaesthetic and corticosteroid — is injected into the joint capsule under pressure to physically stretch it. It is more involved than a standard injection and is most useful in the frozen phase when stiffness is the dominant complaint. UK FROST showed hydrodilatation had broadly similar outcomes to manipulation under anaesthesia and to arthroscopic release at 12 months in the studied population, with the lowest procedural risk profile.

When is arthroscopic release needed?

Arthroscopic capsular release is reserved for the minority of patients in whom stiffness is severe and persistent despite 6–9 months of well-conducted non-operative treatment, and for post-operative or post-fracture stiffness that has not resolved with rehabilitation. Diabetic frozen shoulder is also often more responsive to release than to injection alone.

Will physiotherapy fix it?

Physiotherapy is supportive but is not the primary treatment. In the freezing (painful) phase, aggressive physiotherapy can worsen the inflammation and is counter-productive. Gentle range-of-motion work within the pain-free range, posture and scapular control, and pain-management strategies are appropriate. After injection or release, structured physiotherapy is critical to maintain the regained range.

Why won't my shoulder move? — the frozen shoulder in plain English

What is actually happening inside the joint.

The shoulder is a ball-and-socket joint wrapped in a connective-tissue sleeve called the capsule. In a healthy shoulder the capsule is elastic enough to let the head of the humerus glide and rotate through a very large range of motion — the largest of any joint in the body. In a frozen shoulder, the capsule becomes inflamed, then progressively thickened and scarred. The space inside the joint physically shrinks. The shoulder loses range in every direction, but particularly in external rotation — the movement you use to put a hand behind your head.

The proper medical name is adhesive capsulitis. It is a real, biologically distinct condition with consistent histology: inflammatory infiltrate early, then fibroblastic proliferation, then dense collagen scarring. It is not a vague catch-all term for a stiff sore shoulder, and it is not the same condition as a rotator cuff problem — though the two can coexist.

Who gets it.

Age 40–60 is the typical demographic. It is unusual under 35 and unusual after 70.
Women are affected more often than men.
Diabetes — both type 1 and type 2 — substantially increases the risk and tends to make the condition more resistant to non-operative treatment. The mechanism is thought to be glycation of capsular collagen.
Thyroid disorders, particularly hypothyroidism, are an over-represented association.
Immobilisation after any shoulder injury, fracture or operation can trigger a secondary frozen shoulder — even a relatively brief sling period in a susceptible patient.

In primary frozen shoulder there is no identifiable trigger — the shoulder simply begins to seize up over weeks. In secondary frozen shoulder it follows a clear event — a fall, a fracture, a rotator cuff tear, a surgery.

The three phases — and why "wait it out" is a real answer but not the whole answer.

Frozen shoulder runs a predictable three-phase course. The total time from onset to full recovery is typically 18 to 24 months.¹

Freezing — 2 to 9 months. Pain dominates. The shoulder aches at rest, hurts at night, and is exquisitely painful at the end of every movement. Range of motion is still reasonable early in this phase but progressively narrows. Most people present to a GP in this phase, often because they cannot sleep on the affected side.
Frozen — 4 to 12 months. Pain begins to ease. Stiffness becomes the dominant complaint. The shoulder feels locked — you cannot reach behind your back, you cannot fasten a bra, you cannot put a wallet in a back pocket. Pain at the end of range persists but the rest-pain settles.
Thawing — 6 to 24 months. Range gradually returns. Most patients regain functional motion. A small minority have permanent residual stiffness, particularly in external rotation.

The "it will get better on its own" advice is true on average. It is also unhelpful as a treatment plan, because the average is 18 to 24 months of significant impairment — that is not nothing. The treatment decisions are about shortening and softening that course.

What we can actually do — and when.

In the painful (freezing) phase.

The goal in this phase is pain control, not range. Aggressive stretching makes things worse.

Ultrasound-guided intra-articular corticosteroid injection. The single most evidence-supported intervention in the early phase. The UK FROST trial — the largest randomised trial in frozen shoulder — showed that early injection meaningfully improves pain at 3 and 6 months, even though it does not change the total length of the condition.² A well-placed injection is often the difference between sleeping at night and not.
Simple analgesia. Paracetamol and short-course NSAIDs. Opioids are a poor fit for a problem that runs over months.
Physiotherapy — gentle and pain-free only. Posture, scapular control, gentle range-of-motion within pain-free limits. Not aggressive end-range stretching. A frozen shoulder pushed through a freezing-phase stretch flares for days.

In the stiff (frozen) phase.

Pain is settling. The complaint is now I can't reach.

Hydrodilatation. An image-guided procedure that injects a larger volume of fluid — saline plus local anaesthetic plus corticosteroid — into the joint under pressure to physically stretch the capsule. The UK FROST trial showed hydrodilatation had comparable outcomes to manipulation under anaesthesia and to arthroscopic release at 12 months, with the lowest procedural risk profile of the three.² It is the workhorse intervention for the patient with significant stiffness who has not responded to a standard injection.
Structured physiotherapy. Now the stretches earn their place — capsular stretches, sleeper stretch, towel stretch, daily and sustained. A physio who understands the natural history of the condition is worth their weight.

When release earns its place.

Arthroscopic capsular release — a keyhole operation that divides the contracted capsule under direct vision — is reserved for the minority of patients in whom:

Stiffness is severe and persistent despite 6–9 months of well-conducted non-operative treatment.
The shoulder is post-operatively or post-fracture stiff and the contracture is not responding to rehabilitation.
Diabetic frozen shoulder, which is often more resistant to injection and hydrodilatation.
The patient is at a point in life or work where they cannot continue to wait another 9 months for the thawing phase to deliver.

The operation takes 30–45 minutes under general anaesthesia with a regional block, is day-case, and range of motion is restored on the operating table. The challenge afterwards is keeping the range — which is why physiotherapy starts on day 1 and is intensive for the first 4 weeks.

What I tell patients in clinic.

Three things, in order.

The diagnosis matters. Frozen shoulder is over-diagnosed and under-diagnosed in equal measure. A stiff sore shoulder is not automatically a frozen shoulder — it might be a rotator cuff problem, glenohumeral arthritis, calcific tendinitis, or referred neck pain. A careful examination and the right imaging change the answer.
The clock is real. If you genuinely have a primary frozen shoulder, the total course is going to be 18–24 months. That is the biology. The treatment decisions are about how much pain you have to live with along the way, and how stiff the shoulder is by the end.
The right answer at the right time. Injection in the freezing phase. Hydrodilatation in the frozen phase. Release in the small minority that have not turned the corner by 6–9 months. Aggressive physiotherapy in the freezing phase is the wrong answer. A capsular release in the freezing phase is the wrong answer. The right answer is phase-dependent.

The deeper point.

Frozen shoulder is one of the few shoulder problems where doing too much is as harmful as doing too little. The patient who walks in during the freezing phase wanting an operation usually does better with an injection and 8 weeks of patient observation. The patient who walks in during the frozen phase having been told to "just wait it out" for nine months already usually does better with a hydrodilatation than another nine months of patient observation. Matching the intervention to the phase is most of the practice. The video above walks through what this looks like in clinic.

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References

Neviaser AS, Hannafin JA. Adhesive capsulitis: a review of current treatment. Am J Sports Med. 2010;38(11):2346–2356. (Natural history and three-phase model derived from Neviaser RJ, original description 1945.)
Rangan A, Brealey SD, Keding A, et al. Management of adults with primary frozen shoulder in secondary care (UK FROST): a multicentre, pragmatic, three-arm, superiority randomised clinical trial. Lancet. 2020;396(10256):977–989.
Uppal HS, Evans JP, Smith C. Frozen shoulder: A systematic review of therapeutic options. World J Orthop. 2015;6(2):263–268.
Cucchi D, Marmotti A, De Giorgi S, et al; SIGASCOT Research Committee. Risk factors for shoulder stiffness: current concepts. Joints. 2017;5(4):217–223.

Why won’t my shoulder move? — the frozen shoulder in plain English.