1)      Severe extremity pain disproportionate to the injury, paresthesiae or anesthesia to light touch, passive stretching of involved muscles very painful,  later pallor, pulseless limb, and muscle weakness appear (Acute exertional compartment syndrome) 

2)      Recent onset unilateral leg swelling in the presence of DVT risk factors

3)      Migrating superficial vein thrombosis (marker of carcinoma, vasculitis)

4)      Acute onset severe leg pain in a patient with Diabetes or peripheral vascular disease, paresthesiae, pallor, pulselessness (acute limb ischemia – within 6 hrs irreversible damage to muscles and nerves)