When a Blood Clot Strikes Your Calf

Pain and swelling of the calf may be symptoms of superficial thrombophlebitis.
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That red, ropy vertical line that just appeared on your calf could be more than just a nuisance. There's a chance it could be a sign that a more serious problem is brewing within one of your blood vessels.


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What Is Superficial Thrombophlebitis?

"A red line on the calf could be a sign of inflammation in the veins that is most frequently associated with a blood clot and should be taken seriously," warns Maja Zaric, MD, an interventional cardiologist at Lenox Hill Hospital in New York City. The medical name for this condition is superficial thrombophlebitis, or ST, for short.


The blood clot is usually located just below the surface of the skin. These clots may form in an existing varicose vein — if the vein is big enough, blood can pool and then clot, according to the Cleveland Clinic. STs can also occur after an injury in your lower leg. STs sometimes appear in your arms after having an intravenous line placed there.


"You will likely also notice swelling and your calf may be painful at both activity and at rest," Dr. Zaric says.

Often, STs are not dangerous and may not even require treatment, but some evidence suggests that STs increase your chances of developing a potentially fatal deep venous thrombosis (DVT), according to an article published in February 2018 by Cochrane, a British nonprofit that focuses on medical research.


If a DVT forms in the deep veins of your legs, the clot can break free and travel to your lungs, causing a pulmonary embolism. As many as 20 percent of people with an ST also have a DVT. If your calf pain and swelling occur after a long plane flight or a prolonged period of inactivity, it raises suspicion of a DVT, Dr. Zaric says.

Read more: Exercises to Stop Your Legs From Clotting on Airline Flights

It's always better to be safe than sorry. See your doctor for an ultrasound to determine if the red line on your calf is a blood clot, states the Cleveland Clinic. Your doctor can also order a blood test to see if there is any underlying inflammation. Other potential causes for the red line may include cellulitis, an insect bite or another type of infection, she says.

The pain, swelling and the red line, with proper treatment, typically resolves in a week or two, according to Tufts Medical Center. Taking anti-inflammatory medication and applying warm compresses may improve thrombophlebitis symptoms, says Mayo Clinic. Any swelling or inflammation can be lessened by elevating your legs, wearing compression hose and staying active, adds Mayo Clinic.

In more serious cases or if you're at risk of developing a DVT, your doctor may prescribe blood-thinning medications that prevent clots from growing or clot-busters, which dissolve blood clots, says Mayo Clinic. If you can't take blood thinners, a filter can be inserted into the main vein in your abdomen to prevent the clot from breaking free and traveling to your lungs.

ST Prevention Tips

The best way to lower your chances of developing a blood clot in your calf is to lead a healthy lifestyle, Dr. Zaric says. Keep your weight in the normal range and, if you smoke, quit. "Being overweight and smoking are risks for developing STs and DVTs," she warns.

Other risks, says Mayo Clinic, include advancing age, use of birth control pills or hormone replacement therapy, a family history of a blood-clotting disorder, prolonged immobility such as long flights, being in cast or being bedridden and having had previous episodes of STs or DVTS.

Because these blood clots usually form in varicose veins, having a procedure to destroy the vein can help stave off future episodes. For instance, a procedure called sclerotherapy involves injecting a solution into a varicose vein so that it collapses and disappears, notes Cleveland Clinic. Several treatments may be needed. Veins can also be sealed using laser or radiofrequency energy, or they can be removed surgically.

Read more: Leg Veins and Pain After Exercise