The clinical diagnosis of [[Deep-Vein Thrombosis]] is very unreliable. A patient with the “classic signs” of a hot, swollen, and tender [[calf]] or a positive [[Homans’ sign]] (calf pain on dorsiflexion of the ankle) will have a Deep-vein thrombosis only 20–50% of the time ((Hamilton MG, Hull RD, Pineo GF. Venous Thromboembolism in Neurosurgery and Neurology Patients: A Review. Neurosurgery. 1994; 34:280–296)). 50–60% of patients with Deep-vein thrombosis will not have these findings.