About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Pain out of proportion to the injury is the EARLIEST and MOST RELIABLE symptom
- Pain on PASSIVE STRETCH of muscles within the compartment is the most important clinical sign
- Most common site: anterior compartment of the leg (typically after tibial shaft fracture)
- Clinical diagnosis — do NOT wait for compartment pressure measurement if clinically suspected
- Treatment: EMERGENCY fasciotomy — delay causes irreversible muscle necrosis and nerve damage within 6 hours
Overview
Compartment syndrome occurs when pressure within a closed osseofascial compartment rises sufficiently to reduce capillary blood flow, causing tissue ischaemia. If not decompressed, irreversible muscle necrosis and nerve damage occur within 6 hours, progressing to Volkmann ischaemic contracture (upper limb) or permanent disability. The most common cause is fracture (particularly tibial shaft fracture), but it can occur after crush injury, burns, tight casts/dressings, revascularisation after ischaemia, and bleeding disorders. The anterior compartment of the lower leg is the most commonly affected.
Epidemiology
Compartment syndrome complicates approximately 2–9% of tibial shaft fractures. It is more common in young men (higher muscle mass, tighter compartments). Other causes include supracondylar fractures in children (forearm compartment syndrome), forearm fractures, crush injuries, and burns. It can occur without fracture (e.g. post-exercise, anticoagulation with bleeding into a compartment).
Clinical Features
Symptoms
Pain out of proportion to the injury — the EARLIEST and MOST IMPORTANT symptom
Pain not relieved by adequate analgesia (including opioids)
Increasing analgesic requirements
Numbness or paraesthesiae (nerve ischaemia — late sign)
Signs
Pain on PASSIVE STRETCH of muscles within the affected compartment (most important sign) — e.g. pain on passive toe extension in anterior compartment syndrome
Compartment feels tense and swollen on palpation (woody hard)
Sensory deficit (nerve ischaemia — late sign)
Weakness or paralysis (motor nerve ischaemia — VERY late)
Pulse is usually PRESENT (compartment syndrome occurs at pressures below arterial occlusion) — absence of pulse is NOT required
Investigations
First-line
CLINICAL DIAGNOSISCompartment syndrome is a CLINICAL diagnosis — do NOT delay treatment for investigations. If clinically suspected, proceed to fasciotomy
Second-line
Compartment pressure measurementUsing a handheld pressure monitor (Stryker). Delta pressure (diastolic BP minus compartment pressure) <30 mmHg = diagnostic. Absolute pressure >30 mmHg also concerning. Useful if clinical assessment difficult (e.g. unconscious patient, nerve block)
Specialist
Post-operative bloodsCK (rhabdomyolysis from muscle necrosis), U&Es (renal function — myoglobinuria can cause AKI), lactate
Management
BOA Standards for Trauma (BOAST)1
Immediate measures
- Remove ALL external constrictions: split cast completely to skin, remove dressings, remove circumferential bandages
- Elevate limb to heart level (NOT above — this reduces perfusion pressure)
- Give adequate analgesia — but increasing pain requirements should raise suspicion
- Monitor closely: serial clinical assessment, frequent neurovascular observations
2
Emergency fasciotomy
- Definitive treatment: surgical decompression of ALL compartments in the affected limb
- Leg: 4 compartments (anterior, lateral, superficial posterior, deep posterior) — opened via 2 incisions
- Forearm: volar and dorsal compartments
- Fasciotomy wounds are left OPEN — delayed primary closure or skin grafting at 48–72 hours
- Delay >6 hours leads to irreversible necrosis — time is critical
Complications
- Volkmann ischaemic contracture: Forearm muscle necrosis → fibrosis → fixed flexion contracture of wrist and fingers (late complication of missed compartment syndrome)
- Rhabdomyolysis and AKI: Myoglobin release from necrotic muscle → myoglobinuria → acute kidney injury. Requires aggressive IV fluid resuscitation
- Permanent nerve damage: Foot drop (common peroneal nerve) from anterior compartment syndrome
- Amputation: In severe cases with extensive necrosis
- Infection: Open fasciotomy wounds — risk of surgical site infection
UKMLA Exam Tips
- 15 Ps: Pain (out of proportion), Pain on passive stretch, Pressure (tense compartment), Paraesthesia, Paralysis (late) — but PULSE IS USUALLY PRESENT
- 2Pain on passive STRETCH is the most important clinical sign — not loss of pulse
- 3Presence of a pulse does NOT exclude compartment syndrome — a critical exam point
- 4Most common association: tibial shaft fracture → anterior compartment syndrome
- 5In children: supracondylar fracture → forearm compartment syndrome → Volkmann contracture
- 6Emergency fasciotomy — do NOT wait for pressure measurements if clinically obvious
- 7After fasciotomy: wounds left OPEN — delayed closure/grafting at 48–72 hours
Put your reading into practice
Topic-specific question practice is not linked for this article yet.
Choose UKMLA questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.
Choose UKMLA practiceAfter your session, return to this section to revisit the reading and choose your next review.
Verified Sources & References
related resources
Save your place and choose what comes next
Musculoskeletal · Article 14 of 22