Sometimes people develop a painful hard knot in the leg which may actually be a clot in a superficial vein. This problem is called superficial thrombophlebitis or STP. It is painful, warm, red, and very tender. STP is best treated with NSAIDs (nonsteroidal anti-inflammatory drugs like aspirin and ibuprofen), along with warm compresses. Sometimes blood thinners are required if the clot is extensive. Emergency rooms and walk-in clinics often prescribe antibiotics, which are unnecessary as there is no infection. The redness associated with phlebitis is due to the intense inflammatory response to the clot. This response is blunted by NSAIDs and will dissipate in a few days.