Symptoms of Lower Extremity Compartment Syndrome
Pain out of proportion to the injury is the earliest and most reliable warning sign of acute compartment syndrome, followed by pain on passive stretch of the affected muscle compartment, which is considered the most sensitive early clinical finding. 1
The Classic "5 P's" – Understanding Their Diagnostic Value
The traditional teaching of the "5 P's" must be understood in context of their timing and reliability:
Early Signs (High Sensitivity, Act on These)
Pain (severe, out of proportion to injury) – This is your first and most important clue. Severe pain alone gives only ~25% chance of correctly diagnosing compartment syndrome, but its presence should trigger immediate heightened surveillance. 1
Pain on passive stretch – When you passively extend or flex the muscles in the affected compartment, the patient experiences severe pain. This is the most sensitive early clinical finding. 1 When combined with severe pain, the positive predictive value increases to 68%. 1
Pressure/Tension – The compartment feels increasingly firm and tense on palpation as intracompartmental pressure rises. 1 However, critical pitfall: palpation alone is unreliable (sensitivity only 54%, specificity 76% in children) and should never be used in isolation. 1
Paresthesias – Sensory changes (numbness, tingling) result from nerve ischemia and serve as an early warning sign. 1 The presence of paresthesia has been shown to be significantly associated with the need for fasciotomy. 2
Late Signs (High Specificity but Indicate Irreversible Damage)
Paresis (motor weakness/paralysis) – This is a late manifestation indicating substantial tissue damage. 1 When pain, pain on passive stretch, AND paralysis are all present, positive predictive value reaches 93%, but at this stage irreversible muscle ischemia has likely already occurred. 1
Pulselessness and Pallor – These represent late signs of arterial occlusion and usually reflect a missed diagnosis with likely irreversible injury. 1 Do not wait for these signs before intervening. 1
Additional Clinical Findings
Escalation in leg pain and changes in sensation are the cardinal signs rather than reliance on assessing for firm compartments and pressures. 3
Subjective complaint of pressure by the patient should alert you to possible compartment syndrome. 4
Pain unrelieved with analgesia – Extreme pain that does not respond to appropriate pain medication is highly concerning. 4
Critical Diagnostic Considerations
Clinical signs alone have low sensitivity but high specificity and high negative predictive value for diagnosing acute compartment syndrome. 1 This means a negative exam does not exclude the diagnosis, especially in high-risk patients.
The combination of clinical signs improves diagnostic accuracy algorithmically: severe pain + pain on passive stretch = 68% PPV; adding paralysis = 93% PPV (but too late for optimal intervention). 1
In obtunded, sedated, confused, or uncooperative patients where clinical signs cannot be reliably elicited, proceed directly to compartment pressure measurement. 1
High-Risk Scenarios Requiring Heightened Surveillance
Monitor repetitively (every 30-60 minutes) during the first 24 hours in patients with: 5
- Tibial fractures (especially in young men under 35 years) 1
- Crush injuries or high-energy trauma 1
- Vascular injuries 1
- Hemorrhagic injury or reperfusion of ischemic lesions 5
- Hypotension 5
- Patients on anticoagulation 1
- Burns or penetrating trauma 1
Common Pitfalls to Avoid
Never wait for late signs (pulselessness, pallor, paralysis) before intervening—these indicate already irreversible injury. 1
Never rely solely on palpation for diagnosis; its sensitivity is only about 54%. 1
Never elevate the limb excessively when compartment syndrome is suspected, as this further decreases perfusion pressure and aggravates ischemia. Keep the limb at heart level. 1
Never delay in obtunded patients—the severity of nerve injury worsens with delay in performing fasciotomy. 3 Proceed directly to pressure measurement and surgical consultation.