Blood clots can occur in the deep veins of the legs, a condition known as deep vein thrombosis (DVT). This clot can break off and travel to the lungs, causing a potentially fatal condition called pulmonary embolism. Leg pain is one of the most common symptoms associated with DVT. Understanding the characteristics of this leg pain can help determine if someone may have a DVT that requires urgent medical evaluation.
What Causes Blood Clots in the Legs?
Blood clots form when the blood thickens and clumps together. There are several risk factors that can promote blood clot formation in the leg veins:
- Prolonged immobility – Long periods of sitting still, such as during long car or plane rides, cause the blood to pool and slow down in the legs. This makes clot formation more likely.
- Injury – Damage to blood vessels from surgery, fractures, or other trauma can expose the blood to clot-promoting proteins.
- Pregnancy – Pregnant women have higher levels of clot-forming substances and the uterus can press on veins and restrict blood flow.
- Medical conditions – Cancer, heart failure, inflammatory diseases, high cholesterol, and genetic factors increase clotting risk.
- Medications – Birth control pills, hormone therapy, and other drugs can influence clotting factors.
- Obesity – Excess weight strains the veins and increases risk.
- Older age – The risk of clotting gradually increases with age as the blood vessels and blood flow become compromised.
With immobilization, injury, surgery, pregnancy, and certain medical disorders, a blood clot can form within days. Chronic underlying conditions and risk factors tend to cause clots to develop over longer periods.
Signs and Symptoms of a Blood Clot in the Leg
Some blood clots are small and do not cause symptoms initially. But many clots will eventually produce warning signs and symptoms. These can include:
Pain in the Leg
Leg pain is often the first symptom and most common complaint with a DVT. The pain often starts in the calf and can feel like a charley horse, muscle cramp, soreness, or tightness. It may only occur when standing or walking.
Swelling in the Leg
As the blood clot obstructs normal circulation, fluid can leak into the tissues. This causes swelling, often of just one leg. The calf or entire leg can become visibly enlarged and feet or ankles puffy.
Redness and Warmth
The affected leg may appear flushed, red, and warm to the touch. This is caused by excess blood flow to the area around the clot.
Veins Appear Larger and More Visible
The clotted vein often appears as a hard, swollen, tender cord under the skin. Nearby surface veins suddenly become dilated and twisted.
Leg Fatigue, Weakness, Numbness
A DVT can obstruct blood flow and oxygen to the muscles and nerves of the leg. This causes unusual fatigue, weakness, or numbness.
What Does Blood Clot Leg Pain Feel Like?
The leg pain associated with a DVT has some unique characteristics to help distinguish it from muscular pain or nerve pain. The quality of the pain is often described as:
- Aching – The pain has a dull, throbbing, sore quality.
- Unilateral – It occurs in just one leg, not both.
- Gradual onset – It starts slowly and worsens over hours or days.
- Constant – It can feel nonstop and persistent.
- Localized – Pain centers in the calf or back of the knee.
- Worse with activity – More intense when standing or walking.
- Relieved by rest – Lessens or goes away when leg is elevated.
The pain may be mild at first but becomes progressively worse over time. Swelling in the leg frequently accompanies the discomfort. Changing positions or levels of activity does not necessarily impact the pain from muscle or nerve problems like it does with a DVT.
Are Other Leg Pains Confused with Blood Clots?
Because there are many causes of leg pain, doctors do not want to miss a blood clot. However, most leg pain is caused by musculoskeletal injuries or other non-threatening conditions. Some examples of leg pain that should not be confused with a DVT include:
Muscle Cramps
Painful muscle spasms and charley horses are extremely common. They cause tight, knotted, squeezing pains. Cramps are often related to overuse, muscle fatigue, or electrolyte imbalances.
Strained Muscle
Muscle strains from athletic activities or accidents can cause pain, inflammation, and limping. This pain tends to be more focal with sudden acute onset compared to a DVT.
Knee Bursitis
The bursa sacs around the kneecap can become irritated and inflamed. This causes localized pain and tenderness over the knee.
Tendinitis
Overuse can cause swelling and soreness in the tendons around the knee and ankle. Tendinitis produces pain when moving the joint.
Arthritis
Joint inflammation from osteoarthritis or inflammatory types of arthritis causes dull, aching pains. It often affects both legs instead of just one.
Nerve Pain
Irritated or damaged nerves from conditions like sciatica or a pinched nerve can radiate pain down the leg. The pain tends to shoot, tingle, or burn.
Leg Ulcers
Open sores on the lower legs are common with conditions like varicose veins and diabetes. These are often painful.
Risk Factors for Developing a Blood Clot in the Leg
Anything that slows blood flow or thickens the blood increases clotting risk. The major factors that predispose someone to developing a DVT include:
| Risk Factor | Description |
|---|---|
| Surgery or Trauma | Injury and surgical procedures, especially of hips or knees, can trigger DVT formation. Surgery for cancer also increases risk. |
| Immobility | Long periods of inactivity, like being bedridden, on long flights, or with lower limb casting. |
| Pregnancy and Postpartum | Clotting risk is higher during pregnancy and the first 3 months after giving birth. |
| Birth Control Pills | Estrogen found in oral contraceptives can increase clotting factors. |
| Cancer | Certain cancers raise risk due to secretion of pro-clotting substances. |
| Overweight and Obesity | Excess weight strains leg veins and lowers blood flow. |
| Older Age | Risk gradually increases over age 40, with people over 60 at highest risk. |
| Varicose Veins | Twisted, enlarged leg veins slow blood flow and clotting. |
| Smoking | Chemicals in smoke increase clotting factors. |
| Medical Conditions | Heart failure, lung disease, inflammatory bowel disease all increase DVT risk. |
Those with any combination of these risk factors are more likely to develop a DVT, especially if immobilized or following surgery.
When to See a Doctor for Leg Pain
Leg pain with swelling should be evaluated urgently if it starts after hospitalization, surgery, immobility, or cancer treatment. Seek immediate medical care for leg pain with:
- Sudden onset for no clear reason
- Rapid worsening within hours or days
- Shortness of breath or chest pain
- Calf tenderness, warmth, and redness
- Severely swollen leg
- No relief from elevation and rest
Even without other symptoms, recurrent or persistent leg pain, especially with swelling should be evaluated within several days. Be sure to explain all medications, medical conditions, and any potential risk factors to the doctor. Prompt detection and treatment of a DVT can help prevent complications like pulmonary embolism.
How is a Blood Clot Diagnosed?
If a DVT is suspected, the doctor will perform an examination of the legs to check for swelling, discoloration, and enlarged veins. A D-dimer blood test can help rule out a clot if it is normal. Definitive diagnosis is made by ultrasound of the legs, which can accurately visualize the location and size of a clot. Other tests like CT and MRI scans may also be used in some cases.
Treatment for a Blood Clot in the Leg
Anticoagulant (blood thinner) medications are the mainstay of treatment. They help dissolve the clot and prevent new ones from forming. Commonly prescribed anticoagulants are:
- Heparin – Works immediately and can be injected or given intravenously.
- Warfarin – Taken orally but can take several days to start working.
- Direct oral anticoagulants – Dabigatran, rivaroxaban, apixaban – Taken orally with fewer interactions.
The length of therapy varies but is typically 3-6 months or longer for severe clots. Compression stockings help reduce leg swelling and discomfort. For large clots, a procedure called catheter-directed thrombolysis may be done to break up the clot more rapidly. After the acute phase has resolved, walking and eventual resumption of normal activity is encouraged.
Complications of an Untreated Blood Clot
Leaving a DVT untreated raises the risk of several harmful and potentially fatal complications:
Pulmonary Embolism
A piece of the blood clot can break free and travel through the veins up to the lungs, blocking blood flow. This is called a pulmonary embolism (PE) and can quickly become life-threatening.
Post-Thrombotic Syndrome
Damage to the vein from the clot produces long-term symptoms even after the clot has gone. This post-thrombotic syndrome can lead to chronic leg pain, swelling, varicose veins, and skin changes.
Leg Ulcers
Poor circulation in the legs related to residual venous damage can cause painful open sores that are difficult to heal.
Repeat Blood Clots
Those who have had one DVT are at increased risk for recurrent clots, especially without adequate treatment.
The consequences of an untreated DVT highlight the importance of prevention, early detection, and prompt treatment.
Prevention of Blood Clots in the Legs
For those at high risk, several preventive measures can help lower the chances of developing a dangerous blood clot:
- Blood thinners – Medications like heparin or warfarin may be used prophylactically in some at-risk patients.
- Compression stockings – Gently squeeze the legs to keep blood circulating for immobile patients.
- Early ambulation – Start walking as soon as possible after surgery.
- Avoid dehydration – Drink plenty of fluids to prevent thickened blood.
- Exercise – Regular physical activity strengthens circulation.
- Healthy weight – Don’t be overweight or obese.
- Elevate legs – While sedentary, prop up legs so blood can flow back.
- Stop smoking – Smoking impairs circulation.
- Medication review – Evaluate risks from hormones, birth control, etc.
For travelers, hydrating well, walking on the plane, and doing leg exercises helps minimize risk of clotting during long flights. See a doctor about unexplained leg pain swelling that arises during or after travel.
Conclusion
Leg pain, swelling, tenderness, warmth, and enlargement of surface leg veins can signal a DVT blood clot. Risk is increased with surgery, trauma, prolonged immobility, pregnancy, cancer treatment, obesity, smoking, age over 60 years old, and certain medical conditions. Typical DVT pain often starts gradually in the calf, worsens with walking, and improves with rest and elevation. While many minor leg pains resolve quickly, persistent or recurrent symptoms together with risk factors warrant urgent evaluation for blood clot, as delay can allow life-threatening pulmonary embolism. With proper diagnosis and care, the complications of DVT can be avoided. Preventive measures like early ambulation, compression stockings, leg exercises, staying hydrated, and blood thinners in high-risk patients help reduce incidence. Being aware of the symptoms and risk factors for DVT allows for prompt treatment.