Compartment syndrome
Pain out of proportion and pain on passive stretch. Split the plaster to the skin and call the senior. A pulse doesn't rule it out.
A 22-year-old man had an intramedullary nail for a tibial shaft fracture 8 hours ago. He is asking for more and more morphine. His leg is tense. Moving his toes up and down is agony. Foot pulses are present and the foot is warm.
Is this compartment syndrome even with good pulses, and what do you do right now?
- Pain out of proportion and pain on passive stretchThe earliest and most reliable signs.
- Pulses don't rule it outPulses are usually present until very late.
- Remove or split all dressings and castsDown to the skin, split the padding too.
- Leg at heart levelNot raised (raising lowers perfusion pressure).
- Fluids, oxygen if low, treat low BPMaintain perfusion.
- Call the orthopaedic registrar nowFasciotomy is the treatment.
- Compartment pressureIf the diagnosis is unclear or the patient can't report pain.
- Pain out of proportion to the injury
- Pain on passive stretch
- Rising analgesic needs
- Tense swollen compartment
- Numbness or tingling
- Dark urine (rhabdomyolysis)
- Compartment syndrome in sedated or unconscious patients
- After nerve block or epidural (pain masked)
- Crush injuries
- Rhabdomyolysis and hyperkalaemia
- Forearm compartment syndrome after supracondylar fracture in children
| Delta pressure | Diastolic BP minus compartment pressure under 30 mmHg suggests compartment syndrome |
| Time to irreversible muscle damage | Starts after about 6 hours |
| Fasciotomy | As soon as possible once diagnosed |
| Most common site | Lower leg (anterior compartment), after tibial fracture |
| Position | Limb at heart level |
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On this page
What happens
Pressure in a closed fascial compartment rises (bleeding, swelling, tight casts). When it exceeds capillary pressure, blood flow to muscle and nerves stops. Muscle death begins after about 6 hours. Arterial pulses stay present because arterial pressure is much higher than compartment pressure.
Causes
- Fractures (tibia most common, also forearm).
- Crush injury, prolonged lying (after a fall or overdose).
- Tight casts and dressings.
- Reperfusion after vascular surgery.
- Burns (circumferential).
- Bleeding into a compartment (anticoagulants, haemophilia).
- Snake bite (rare; antivenom first).
- Extravasation of IV fluid.
Signs
- Pain out of proportion to the injury.
- Pain on passive stretch of the muscles in the compartment.
- Increasing need for analgesia.
- Tense, swollen compartment.
- Numbness or tingling.
- Weakness or paralysis.
- Pale, pulseless limb (very late or arterial injury).
Management
- Remove constrictionSplit cast and padding down to the skin; remove dressings.
- PositionLimb at heart level.
- Support perfusionTreat hypotension, oxygen if low, IV fluids.
- Reassess within 30 minutesPain, passive stretch, tension.
- Not improvingOrthopaedics: emergency fasciotomy.
- Uncertain or unconsciousCompartment pressure measurement.
Lower leg compartments
| Compartment | Passive stretch that hurts | Nerve |
|---|---|---|
| Anterior | Pointing the toes down (plantar flexion) | Deep peroneal (numb first web space) |
| Lateral | Turning the foot inward (inversion) | Superficial peroneal |
| Superficial posterior | Pulling the foot up (dorsiflexion) | Sural |
| Deep posterior | Extending the toes | Tibial (numb sole) |
Investigations
| Test | Why |
|---|---|
| Compartment pressure | Unclear diagnosis or unconscious patient |
| Creatine kinase | Muscle damage |
| U&E, potassium | Rhabdomyolysis, kidney injury |
| Urine dipstick | Blood with no red cells suggests myoglobin |
Treatment
The treatment is fasciotomy. Analgesia and fluids support the patient while the surgeons come.
Common mistakes
- Reassured by present pulses.
- Elevating the limb.
- Giving more morphine without examining the leg.
- Splitting the cast but leaving tight padding.
- Missing it in a patient with a nerve block or reduced consciousness.
- Waiting for numbness or weakness.
Frequently asked questions
What is the earliest sign of compartment syndrome?
Pain out of proportion to the injury, and pain on passive stretch of the muscles.
Can you have compartment syndrome with normal pulses?
Yes. Pulses are usually present until very late.
What is the treatment for compartment syndrome?
Remove constricting casts and dressings, keep the limb at heart level, support perfusion and arrange urgent fasciotomy.
Which fracture most often causes compartment syndrome?
Tibial shaft fractures.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A man has a tibial fracture fixed today. He has severe calf pain despite morphine and pain on passive toe movement. The foot pulse is present. What is the next step?
Answer: Split dressings to skin, call senior. Compartment syndrome is a clinical diagnosis. Release everything to the skin, keep the limb at heart level and arrange urgent fasciotomy.
- Reassure because the pulse is present: A pulse doesn't exclude it.
- Doppler for DVT: Not the priority.
- Increase the morphine and review in 4 hours: Delay causes muscle death.
- Elevate the leg high: Elevation reduces arterial inflow.
2. Which is the earliest and most reliable sign of compartment syndrome?
Answer: Disproportionate pain. Pain out of proportion and pain on passive stretch are early signs. Pulselessness and paralysis are late.
- Pallor: Unreliable.
- Absent pulse: A late sign.
- Cold limb: Usually late or absent.
- Paralysis: A late sign.
3. A sedated patient has a tense leg compartment. Diastolic BP is 60 mmHg and compartment pressure is 40 mmHg. What does this mean?
Answer: Fasciotomy is indicated. A difference between diastolic and compartment pressure below 30 mmHg supports the diagnosis.
- Normal pressures: Below 30 mmHg perfusion pressure is abnormal.
- Start enoxaparin: Not relevant.
- Repeat in 12 hours: Too slow.
- Elevate and observe: Inappropriate.
4. After damage-control laparotomy and massive transfusion, a patient has a tense distended abdomen, falling urine output and rising ventilatory pressures; bladder pressure is 28 mmHg. What is the treatment?
Answer: Decompressive laparotomy. Abdominal compartment syndrome: sustained intra-abdominal pressure > 20 mmHg (measured via bladder) with new organ dysfunction — causes: massive fluid resuscitation, haemorrhage, bowel oedema, pancreatitis, burns, packing. Effects: oliguria/AKI, raised airway pressures, hypoxia, reduced venous return/cardiac output, gut ischaemia. Management: decompress (NG, sedation/paralysis, drain ascites), avoid over-resuscitation; decompressive laparotomy with temporary abdominal closure (laparostomy) if persistent.
- More IV fluids: More fluid worsens abdominal compartment syndrome.
- Furosemide infusion alone: Furosemide does not relieve the pressure.
- Observe for 24 hours: Waiting causes organ failure.
5. Six hours after a plaster cast was applied for a tibial fracture, a 24-year-old man has severe pain not relieved by morphine. Pain increases when his toes are passively stretched. Foot pulses are present. What is the most likely diagnosis?
Answer: Compartment syndrome. Compartment syndrome occurs when pressure in a closed fascial compartment rises and compromises perfusion. Pain out of proportion and pain on passive stretch are the earliest signs; pulses are usually present until late. Split the cast down to skin, elevate to heart level (not above) and arrange urgent fasciotomy.
- Deep vein thrombosis: Doesn’t cause pain on passive stretch within hours.
- Arterial occlusion: Pulses would be absent and the limb pale.
- Normal fracture pain: Normal fracture pain settles with morphine; pain out of proportion that increases on passive stretch is compartment syndrome.
6. After a tibial shaft fracture, a man has severe pain on passive plantar flexion of the toes and numbness in the first web space of the foot. Which compartment and nerve are involved?
Answer: Anterior; deep fibular nerve. Anterior compartment syndrome: swelling inside the tight fascial compartment compresses the anterior tibial artery and deep fibular nerve. Passive stretch of the toe extensors (plantar flexion) is very painful, and the first web space is numb. Pulses are often still present. Treatment is urgent fasciotomy.
- Lateral; superficial fibular nerve: Supplies skin of most of the dorsum, not the first web space; stretch pain is with inversion.
- Deep posterior; tibial nerve: Stretch pain on passive toe extension; sole numbness.
- Superficial posterior; sural nerve: Lateral foot numbness.
- Medial thigh; obturator nerve: Not in the leg.
7. Why does myoglobin have a hyperbolic oxygen dissociation curve while haemoglobin's is sigmoid?
Answer: Single chain, no cooperativity. Haemoglobin has four subunits; binding of one O₂ increases affinity of the others (cooperativity, T to R state), giving a sigmoid curve suited to loading in lungs and unloading in tissues. Myoglobin is monomeric with high O₂ affinity, so it stores O₂ in muscle and releases it only at very low PO₂.
- Has four haem groups: One haem group.
- Strong 2,3-BPG binding: 2,3-BPG acts on haemoglobin.
- Lower affinity for oxygen: It has higher affinity.
- Iron in the ferric state: Ferric iron (methaemoglobin) cannot bind O₂.
References and dose sources
- BOA standards for trauma (BOASTs), including compartment syndrome
- BOAST — compartment syndrome
- NICE NG37 — fractures (complex)
- Morphine dosing: Drugs.com: Morphine dosage (see also our morphine dose page)
- Sodium chloride (normal saline, 3% saline) dosing: Drugs.com: Sodium chloride dosage (see also our sodium chloride (normal saline, 3% saline) dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.