Knowledge · Acute surgical conditions

Compartment Syndrome and the BOAST Standard

By Dr Alexander Young with the Core Surgery Interview Team · Reviewed 11 September 2026

In brief

The BOAST standard on compartment syndrome says the diagnosis is clinical, on pain out of proportion and pain on passive movement; that dressings are released, the limb elevated and the patient re-evaluated within 30 minutes; and that immediate surgical decompression should follow the diagnosis.

Acute compartment syndrome is raised pressure within a closed fascial compartment that causes tissue ischaemia, and at the CST management and clinical station the answer is the BOAST standard: a clinical diagnosis on pain out of proportion and pain on passive movement, immediate release of dressings, re-evaluation within 30 minutes, senior review, and immediate surgical decompression once the diagnosis is made. According to the British Orthopaedic Association, whose standard was published in July 2014 and last updated in July 2025, early diagnosis and treatment is vital to avoid morbidity.

Key takeaways

The BOAST standard names pain out of proportion to the injury and pain on passive movement of the muscles in the compartment as the key clinical findings
Patients at risk should be assessed hourly with findings, interpretation and rationale documented, whether the signs are present or not
If symptoms or signs appear, circumferential dressings are released to expose the skin, the limb is elevated, and the patient is re-evaluated within 30 minutes
A difference between diastolic blood pressure and compartment pressure of less than 30 mmHg indicates increased risk, and an absolute pressure over 40 mmHg should prompt consideration of urgent decompression
Immediate surgical decompression should follow a diagnosis of compartment syndrome, with open decompression of all involved compartments
Every patient is discussed with a plastic surgeon within 24 hours of fasciotomy and re-explored within 72 hours or earlier

How do I recognise compartment syndrome?

Recognise compartment syndrome by pain out of proportion to the injury and pain on passive stretch of the muscles in the affected compartment, which the BOAST standard names as the key clinical findings.

Pallor, paraesthesia, paralysis and pulselessness are late. A limb with a normal pulse and warm foot can still have a dead anterior compartment, and the panel is checking that you do not wait for the pulse to go.

Ask about the mechanism, the time since injury or surgery, the analgesia given and whether it worked, and the conscious level, because an intubated or obtunded patient cannot report the pain.

How do I assess a limb at risk of compartment syndrome?

Assess a limb at risk with the CCrISP structure: immediate ABCDE management in a trauma patient, then a full assessment that documents time, mechanism, conscious level, neurovascular status, pain level and the response to analgesia, then decide and plan.

The BOAST standard asks for exactly that documentation, and it asks for it hourly in at-risk patients, with an interpretation of the findings and the rationale for management written each time.

Feel each compartment for tenseness, stretch each muscle group passively, and check sensation in the nerve that runs through the compartment, for example the first web space for the anterior compartment of the leg.

What do I do the moment I suspect compartment syndrome?

The moment you suspect compartment syndrome, release every circumferential dressing, split and spread the cast to expose the skin, elevate the limb, and re-evaluate within 30 minutes, as the BOAST standard directs.

Alongside that, give oxygen, ensure the patient is not hypotensive, and give analgesia while telling the senior team that the analgesia requirement itself is a sign. Do not delay the call to see if the review at 30 minutes is better.

When are compartment pressures measured, and what do the numbers mean?

Compartment pressures are measured when the clinical signs are inconclusive or the assessment is incomplete, for example in a sedated patient, and the BOAST standard gives two numbers.

According to the standard, a difference between the diastolic blood pressure and the compartment pressure of less than 30 mmHg indicates an increased risk of compartment syndrome, and if the absolute compartment pressure is greater than 40 mmHg, urgent surgical decompression should be considered.

The standard is clear that the decision to decompress or to continue monitoring on the basis of pressures is made by a consultant orthopaedic surgeon, so say that name rather than the number alone.

What is the definitive management of compartment syndrome?

The definitive management of compartment syndrome is immediate surgical decompression, and the BOAST standard says it should follow a diagnosis of compartment syndrome as an NCEPOD immediate case.

Surgery is open decompression of all involved compartments. For the lower leg the standard recommends a two-incision, four-compartment decompression, using the incisions set out in the BOAST on open fractures.

The wounds are left open. All patients are discussed with a plastic surgeon within 24 hours of fasciotomy and undergo re-exploration within 72 hours, or earlier if clinically indicated, with a documented plan for definitive soft tissue management.

What about a patient who presents late?

A patient who presents late, or whose diagnosis was delayed, has a high risk of complications with surgery, and the BOAST standard says that decision should involve two consultants.

Non-operative management is an option in that group, accompanied by renal assessment and protection, because rhabdomyolysis and myoglobinuria are the systemic threats once the muscle is dead. Say that you would check creatine kinase, potassium and urine output.

Who do I escalate compartment syndrome to?

Escalate suspected compartment syndrome to a senior member of the surgical team with the capacity to make a decision, which in practice means the orthopaedic registrar now and the consultant if pressures or a late presentation are involved.

The standard also addresses regional anaesthesia in limb trauma: it should follow a joint decision by the patient, the anaesthetist and the surgeon, with documented consent and an agreed policy for post-operative monitoring, because a block can mask the pain.

What is the interviewer listening for in a compartment syndrome scenario?

The interviewer is listening for a clinical diagnosis made on pain, dressings released and the limb elevated at once, a 30-minute re-evaluation, the consultant named, and immediate fasciotomy said without hedging.

Pain on passive stretch examined and named, not just tenseness
Hourly documented review in the patient who is at risk but not yet diagnosed
The 30 mmHg differential and 40 mmHg absolute figures attributed to the standard and to a consultant's decision
Plastics within 24 hours and re-look within 72 hours as part of the plan
Awareness that a regional block or an obtunded patient removes your best sign

How this comes up at the CST interview

Compartment syndrome is set as a tibial fracture in a cast, eight hours after surgery, with a nurse reporting that morphine is not working, and the panel wants the cast split and the registrar called in your first two sentences.

Follow-ups probe what you would do if the pulses were normal, what the pressure numbers mean, and how you would handle a registrar who tells you to give more analgesia and review in the morning.

The coresurgeryinterview bank includes a scored compartment syndrome scenario among its 299 questions: /Question-Bank/Sample-Questions.

Key evidence

BOAST: Diagnosis and Management of Compartment Syndrome of the Extremities — British Orthopaedic Association (2025)
BOAST: Open Fractures — British Orthopaedic Association and British Association of Plastic, Reconstructive and Aesthetic Surgeons (2017)

FAQ

What are the key clinical signs of compartment syndrome?

The BOAST standard names pain out of proportion to the injury and pain on passive movement of the muscles in the compartment. Pallor, paraesthesia, paralysis and pulselessness are late signs and their absence does not exclude the diagnosis.

What should happen within 30 minutes?

Once symptoms or signs appear, the BOAST standard says circumferential dressings are released to expose the skin, the limb is elevated, and the patient is re-evaluated within 30 minutes. Senior review is requested in parallel.

What compartment pressure indicates compartment syndrome?

According to the BOAST standard, a difference between diastolic blood pressure and compartment pressure of less than 30 mmHg indicates increased risk, and an absolute pressure above 40 mmHg should prompt consideration of urgent decompression. A consultant orthopaedic surgeon makes the decision.

How quickly should fasciotomy happen?

The BOAST standard says immediate surgical decompression should follow a diagnosis of compartment syndrome, classed as an NCEPOD immediate case. It does not print an hour target, so the answer is now.

What happens after a fasciotomy?

The wounds are left open, the patient is discussed with a plastic surgeon within 24 hours, and re-exploration takes place within 72 hours or earlier if clinically indicated, with a documented plan for soft tissue cover.

Is a late-presenting compartment syndrome still operated on?

Not always. The BOAST standard says delayed presentation carries a high risk of complications with surgery, the decision should involve two consultants, and non-operative management with renal protection is an option.

The Core Surgery Interview Team

Written and maintained by doctors who have sat and scored well at this interview, and reviewed against the current published guideline in each case. Guidance changes — check the source before you rely on a threshold.

Last reviewed 11 September 2026

More in Acute surgical conditions

Acute Appendicitis: Assessment and Management

The WSES 2020 Jerusalem update recommends the AIR and AAS scores rather than the Alvarado score to predict acute appendicitis in adults, ultrasound as the first-line imaging, and laparoscopic appendicectomy on the next available list within 24 hours of admission.

Acute Limb Ischaemia: the Six Ps and Time to Theatre

Acute limb ischaemia is graded by the Rutherford classification, anticoagulated at once with intravenous unfractionated heparin, and revascularised promptly when the limb is threatened; a Rutherford IIb limb with motor loss goes to theatre immediately, and a class III limb is irreversible.

Cauda Equina Syndrome: Red Flags and Emergency MRI

The GIRFT national pathway says suspected cauda equina syndrome with symptoms of under two weeks is an emergency referral for an MRI at the presenting hospital as soon as possible and certainly within four hours of request, in and out of hours, with incomplete CES decompressed as an NCEPOD E1/E2 emergency.

Head Injury and the NICE CT Criteria

NICE NG232 sets the CT head criteria for adults: within 1 hour for GCS 12 or less on arrival, GCS under 15 at 2 hours, suspected open or depressed skull fracture, basal skull fracture signs, post-traumatic seizure, focal deficit or more than one episode of vomiting; within 8 hours for loss of consciousness or amnesia with age 65 or over, a clotting disorder, a dangerous mechanism or more than 30 minutes of retrograde amnesia.

Practise this at interview level

The question bank turns this topic into station-style questions with model answers and AI-marked spoken practice.

Explore the question bank