Minor Leg Injuries May Up Clot Risk

Study Suggests Threefold Increase in Risk

Medically Reviewed by Louise Chang, MD on January 14, 2008
From the WebMD Archives

Jan. 14, 2008 -- Even minor leg injuries, such as ankle sprains or pulled muscles, increase the risk of potentially life-threatening blood clots, new research suggests.

Having a recent minor leg injury, according to a study from the Netherlands' Leiden University, was found to be associated with a threefold increase in the risk of serious blood clots, such as deep vein leg clots and pulmonary embolism (clots that travel to the lung).

Researchers concluded that as many as 8% of these serious blood clots may be caused by minor leg injuries that are not serious enough to require a cast or extended immobilization.

Having a recent minor leg injury was found to increase the risk 50-fold among people with a genetic mutation linked to blood clots.

"These injuries should be taken more seriously than they are today," reseacher Frits R. Rosendaal, MD, PhD, tells WebMD. "Physicians need to be aware that people who have minor leg injuries may be at increased risk."

Leg Clots Can Be Deadly

Major leg injuries that require a cast, surgery, extended bed rest, or immobilization are known risk factors for deep vein clots, known medically as deep venous thrombosis or DVT.

These clots can turn deadly when they travel to the lungs.

It has not been clear whether common leg injuries that require little treatment also impact risk. In a study designed to address the question, Rosendaal and Leiden University colleagues recruited 2,471 patients with a history of deep vein or lung blood clots.

These people completed questionnaires designed to determine if they had had injuries, surgical procedures, plaster casts, or immobilizations because of injury within one year of developing the clots.

Their answers were compared to those of 3,534 people who had no history of deep vein thrombosis.

A total of 289 patients (11.7%) reported that they had experienced a minor injury in the three months prior to a serious blood clot. By contrast, 154 of the participants who had no history of clots (4.4%) reported experiencing a minor injury within three months prior to completing the questionnaire.

Leg injuries, but not injuries to other parts of the body, were associated with an increased risk for serious blood clots, and the association was strongest in the months before the blood clots occurred.

Even minor leg injuries, such as sprains or muscle tears, often lead to reduced mobility, and Rosendaal says this may explain the increase in risk.

Clot Risk Higher in Elderly, Obese

Pulmonologist Victor F. Tapson, MD, of Duke University Medical Center, has studied deep vein blood clots for many years.

He says the new study should serve to raise awareness among doctors and their patients.

"I don't think it would surprise most experts that minor leg injury would be a risk factor for these clots, but it is not something that most clinicians are aware of," he tells WebMD. "This is an important paper."

The findings could be especially important for patients at high risk of developing blood clots, such as those who are elderly, obese, or who have a family history of blood clots.

"These people need to be aware that even minor injuries and a relatively short duration of inactivity could lead to blood clotting," Richard C. Becker, MD, director of the Duke Cardiovascular Thrombosis Center, tells WebMD.

As many as three in 1,000 people develop deep vein clots each year. Although most people who experience minor leg injuries have little to worry about, Rosendaal says everyone should be aware that such injuries can increase their clot risk.

"If you sprain your ankle and your ankle hurts and is swollen, that is to be expected," he says. "But if the calf or thigh begins to hurt or swells too, that is not normal. And if you develop pulmonary symptoms like shortness of breath or pain in the chest, don't ignore them."

Show Sources

SOURCES: van Stralen, K.J. Archives of Internal Medicine, Jan. 14, 2008; vol 168: pp 21-26. Frits R. Rosendaal, MD, PhD, department of clinical epidemiology and thrombosis and hemostasis, Leiden University Medical Center, Leiden, the Netherlands. Richard C. Becker, MD, Cardiovascular Thrombosis Center, Duke University Medical Center, Durham, N.C. Victor Tapson, MD, professor of medicine; director, Center for Pulmonary Vascular Disease, Duke University Medical Center, Durham, N.C.

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