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Homans' sign is a diagnostic indicator that suggests the presence of a clot in the deep veins of a lower extremity. When assessing a patient for the possibility of a deep venous thrombosis (DVT) or blood clot, the physician flexes the patient's knee and forcibly flexes the foot so that the toes turn up. This maneuver applies traction to the major vein in the calf region, the posterior tibial vein. If the patient experiences pain in the calf muscle or behind the knee with this maneuver — a positive Homans' sign — the physician will proceed with further testing, such as venography, to confirm the diagnosis. This sign was first described in an article in 1938 by a surgeon, John Homans, in which he advances his theory that early DVT produces calf muscle congestion and irritability, leading to the pain elicited with the sign.
In addition to deep venous thrombosis, Homans' sign may be present in other conditions of the lower extremity. Diffuse lower extremity swelling from infections or muscle injury may also contribute to pain during knee flexion with tipping up of the foot. Patients with ruptured discs in the lumbar spine with compression of the nerve roots may also present with Homans' sign. Furthermore, women who chronically wear high heels may notice a positive Homans' sign when they switch to flat shoes. This sign is present in about 33 percent of patients with DVT and 20 percent of patients without DVT, indicating that it is not highly specific to DVT.
Since clinical signs of DVT can be unreliable, the diagnosis of DVT mainly depends on confirmation by other diagnostic tests, including impedance plethysmography, venography, and ultrasonography. Impedance plethysmography measures the extent to which the leg tissue impedes the flow of electrical current in the leg with lower impedance pointing to a clot. Venography utilizes a radiopaque dye that will display a blockage in blood flow. Ultrasonography measures the amount of compressibility of the leg veins, with decreased compressibility indicating a clot. Most physicians will use both the clinical presentation, including the presence of a Homans' sign, and ancillary diagnostic tests to assess the likelihood that a patient has DVT.
Deep venous thrombosis occurs when blood coagulates in one of the deep leg veins that transport blood back to the heart. Many patients have no symptoms at all. If the patient receives no treatment, however, the clot may break into pieces, dislodge, and travel to the lung, blocking an artery to the lung tissue. This condition, called a pulmonary embolus, can be life-threatening.