Bruised legby James Hubbard, M.D., M.P.H.

I see this fairly often. Someone comes in with a whopper of a bruise, maybe with a lump, and they’re afraid it’s a blood clot. In a disaster situation, you’re likely to get some bruises, but you won’t be able to come see me. Should you worry?

In short, probably not. You do have clotted blood, but there are blood clots and there “blood clots.” In fact, if your blood doesn’t clot, you could bleed to death.

Bruise-related clotting happens in tissue outside the blood vessels. That’s where the bleeding occurred. What you’re really worried about is a deep-vein thrombosis (DVT)—a clot that forms inside a deep-in-the-tissue vein and can break off and travel to the lungs. DVTs are different, serious, and sometimes lethal.

So a bruise isn’t a serious blood clot. However, can a bruise cause a serious blood clot? No, but the hit that caused the bruise can—though that’s rare.

If the trauma that caused the bruise injures a large and deep-seated vein’s wall, it could make conditions right for a deep-vein clot to form. These veins are deep in the tissue and have to be hit just right. Compared with the number of bad bruises people get, this is rare as hen’s teeth and has to do with the injury to the vein’s inner wall. The bruise to the soft tissue is incidental.


How Can You Tell Whether You Have a DVT?

Even doctors can have a tough time telling whether you have a DVT. Sometimes one forms with very few outside signs. But suspect it if your arm or leg swells and becomes painful—trauma or no trauma.

Since DVTs often form in the calves, one test is the Homans’ sign. Simplified: You lie down, toes up. The doctor takes hold of your relaxed foot’s sole and quickly flexes your foot, pushing your forefoot back. Significant pain in the calf points toward a deep-venous blood clot. But positive Homans’ sign or not, If the doctor is suspicious, he or she will order a special type of ultrasound test that looks inside the veins to find out for sure. If you have DVT, you’ll be started on a blood thinner.

If you can’t get medical help, your best bet for a swollen, red extremity is to keep it immobile, elevate it at heart level or above, and apply a moderate amount of heat to the area. Get to a doctor as soon as you can.


So What If You Have a Bad Bruise That’s Bothering You?

For a bad bruise, treat it with RICE. That’s

  • Rest
  • Ice. Use a commercial type, a frozen bag of vegetables, or ice in a zip-close bag. Put a cloth between the ice and skin. Use it for something like ten minutes on, ten minutes off, repeat.
  • Compression with an elastic bandage—firm, but not to tight. Loosen as needed.
  • Elevation at heart level or above.

Unlike with DVT, using the extremity poses no threat if you just have a bruise.


What If Only the Bruise Is Swollen?

Sometimes, the area bleeds enough for blood to pool in the soft tissue. If this happens, a localized area will be swollen, even baggy. This is called a hematoma. Other than the RICE, leave it alone. It may even shrink to a smaller, firm spot—a blood clot. But it’s outside the blood vessels. To try to drain it outside of a medical facility is to risk infection.

Don’t be surprised if a large area of discoloration shows up days later. It may even travel with gravity down to areas not bruised. That’s a good thing. The blood from the hematoma is spreading out and will be absorbed.


Bottom Line?

Bruise or no bruise, if your extremity swells or hurts, see a health-care professional. You never know. But don’t get too concerned with some marble-sized knot after a fall.

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Photo by Matt Gibson.