## Early Clinical Signs of Compartment Syndrome **Key Point:** **Pain out of proportion to clinical findings, especially pain with passive stretch**, is the **earliest and most sensitive sign** of acute compartment syndrome. It often precedes objective neurological or vascular findings by hours. ### The "5 P's" in Temporal Sequence | Sign | Timing | Sensitivity | Specificity | | --- | --- | --- | --- | | **Pain (especially with passive stretch)** | **Earliest** (0–6 hours) | **Highest** | Moderate | | Pressure (elevated compartment pressure) | Early (0–8 hours) | High | High | | Paresthesia | Intermediate (6–12 hours) | Moderate | Moderate | | Pallor | Late (12–24 hours) | Low | Moderate | | Pulselessness | **Latest** (> 24 hours) | Low | High | ### Why Pain with Passive Stretch Is Most Sensitive 1. **Ischemic muscle is exquisitely pain-sensitive** — even before necrosis begins 2. **Passive stretch increases intracompartmental pressure further**, triggering severe pain in ischemic tissue 3. **Occurs before nerve ischemia** (which causes paresthesia) or vascular collapse (which causes pulselessness) 4. **Disproportionate to visible injury** — the clinical findings (swelling, bruising) do not match the severity of pain **High-Yield:** The classic teaching is: *"If the patient has pain out of proportion and pain with passive stretch, suspect compartment syndrome until proven otherwise."* This is the **single most important red flag** for early diagnosis. **Clinical Pearl:** Late signs (pulselessness, pallor, paralysis, paresthesia) indicate **irreversible tissue damage** and are poor prognostic indicators. Early fasciotomy (within 6–8 hours) depends on recognizing pain with passive stretch, not waiting for late signs. **Mnemonic:** **"PPPPP"** — Pain (earliest), Pressure, Paresthesia, Pallor, Pulselessness (latest). The first P is the most sensitive; the last P is the most specific but comes too late. 
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