A blood clot (a clump of blood) that forms in a vein and causes
inflammation is called thrombophlebitis. Symptoms include pain, tenderness,
warmth, and redness along the length of a vein.
A clot may form either in a vein just under the surface of the skin
(superficial thrombophlebitis) or in a vein deep in the leg (deep vein
thrombosis, or DVT). Clots in a vein just under the skin rarely cause serious
problems because they do not travel through the bloodstream. Once this kind of
blood clot has been diagnosed by a health professional, the person can often
care for the symptoms safely at home.
Thrombophlebitis can occur in any vein, but it is most common in
the leg veins. Clots in a deep leg vein (deep vein thrombosis) are serious
because a clot can break loose and travel through the bloodstream to the lung
(pulmonary embolism). Symptoms of deep vein thrombosis include swelling, pain,
and possibly redness in one leg or a noticeable new difference in the size of
one leg. Another symptom of deep vein thrombosis is pain when walking or when
the foot is flexed upward.