Blood clots that form to halt bleeding after an injury can be life-saving. But clots that form spontaneously within a blood vessel -- in the calf or elsewhere in the body -- could be a sign of trouble. The calves are the most common site of spontaneous blood clots. Signs and symptoms of these clots vary, primarily depending on clot size and whether a superficial or deep vein is involved.
Most blood clots in the calves form in superficial veins near the skin surface. These clots -- known as superficial venous thrombi, or SVTs -- often form in an existing varicose vein. They may also form after a blow to the lower leg. Common symptoms of an SVT in the calf include pain, tenderness and redness at the site of the clot. These clots often cause an obvious cord-like swelling that feels firmer than the surrounding tissue. Bruising may be present if the clot formed due to a calf injury. Small superficial calf clots can occur without any noticeable signs or symptoms. SVTs usually do not pose a serious health threat.
Deep Vein Clots
Blood clots occurring in deep veins are called deep venous thrombi, or DVTs. The calf is one of the most common sites for a DVT, and symptoms vary. Typical symptoms of a calf DVT include achy pain, swelling, warmth and reddened skin below the knee. The superficial veins of the lower leg may bulge and appear more prominent than those of the unaffected leg. A low fever may also be present. Symptom severity generally increases in proportion to the size of the clot. Small clots in the deep calf veins often cause no symptoms.
DVTs are more serious than superficial clots because they can lead to a complication known as a pulmonary embolism. With this condition, part or all of the clot breaks free from the deep leg vein and travels to the lung blood vessels. These traveling clots -- known as emboli -- lodge in the lungs and may significantly reduce blood flow. The size of a pulmonary embolism correlates with symptom severity. Common signs and symptoms of larger pulmonary emboli include chest pain while inhaling, shortness of breath, and rapid heart and breathing rates. Other possible symptoms include cough, dizziness, fainting and low fever. Small pulmonary emboli often do not cause symptoms.
Approximately one-third of people who develop a DVT experience a complication known as postthrombotic syndrome, notes a November 2009 article published in the journal "Blood." Symptoms of this condition after a calf DVT may include lower leg swelling, dull pain, muscle cramps, tingling, itchiness and darkening of the skin over time. Long periods of standing or walking typically make symptoms worse. Resting with the legs elevated often relieves symptoms.
When To Seek Medical Care
See your doctor right away if you experience sudden lower leg swelling, pain, redness or other symptoms that may indicate a blood clot. Get emergency medical care if for symptoms suggestive of a possible pulmonary embolism, including sudden shortness of breath, chest pain, rapid breathing or a racing heart rate. Pulmonary embolism can be life-threatening if not treated immediately.
Is This an Emergency?
- The Merck Manual Professional Edition: Superficial Venous Thrombosis
- Cleveland Clinic Center for Continuing Education: Venous Thromboembolism (Deep Venous Thrombosis & Pulmonary Embolism)
- American Lung Association: Understanding Pulmonary Vascular Disease
- The Merck Manual Professional Edition: Pulmonary Embolism
- The Merck Manual Professional Edition: Deep Venous Thrombosis (DVT)
- Blood: How I Treat Postthrombotic Syndrome