What Causes Swollen Legs from the Knee Down?

Dealing with some random swelling from the knee down? Don’t worry, Willy Wonka isn’t turning you into a blueberry. Rather, this symptom is usually caused by fluid buildup. Sometimes, it’s from something as simple as standing too long. Other times, it can be a sign of a more serious problem. Knowing what to look for helps you know what to do and when to call your doctor.

If your lower legs have started looking puffier than usual, you're probably not imagining it. Swelling is a signal from your body that something’s up. But what causes swollen legs from the knee down, exactly? Sometimes it's gravity doing its thing after a long day on your feet, but other times, it's your body waving a red flag.

The medical term for this kind of swelling is edema. It happens when fluid leaks out of your blood vessels and gets trapped in nearby tissues. Gravity can make that fluid pool in one or both of the lower legs.

“One-sided swelling is often more concerning, as it may indicate a blood clot,” says Annie DePasquale, MD, a board-certified family medicine physician and CEO of Collaborating Docs. "Swelling in both legs is usually related to systemic conditions [like heart, kidney, or liver disease] or medications.”

One-sided leg swelling advice

Another important clue is how quickly the swelling develops. Sudden swelling—especially in one leg—can indicate a serious problem like a blood clot or infection. Gradual swelling that builds up over time is more often associated with chronic conditions like venous insufficiency or heart failure.

That’s why understanding the difference between "just annoying" and "needs a doctor" is key. This guide breaks it down, explaining the most common causes of leg swelling, how to recognize warning signs, and what treatments may help, so you can take the best next step.

What Does “Swelling from the Knee Down” Look Like?

Swelling can be sneaky. One day your legs feel fine, and the next they’re puffy, tight, and stretching your socks like they’re trying to escape. According to Dr. DePasquale, here are the two main types of edema:

• Pitting edema: This can occur due to fluid retention from heart failure, kidney disease, or venous insufficiency. When you press the swollen area with a finger, it leaves a "pit" that slowly fills back in.
• Non-pitting edema: This is more typical in conditions like lymphedema or hypothyroidism. Skin may feel firm or rubbery, and doesn’t pit when pressed.

Aside from the type of swelling, the pattern can tell you a lot, Dr. DePasquale adds. Is the swelling just around your ankle, or does it creep up into your calf or even higher? Is it happening in one leg, or both? Swelling in just one leg often points to something local, like an injury or clot. But if both legs are affected, it could be tied to a broader health issue.

Watch for other clues, too. For instance, if your skin looks shiny, feels tight, or seems tougher than usual, that could signal chronic vein problems, says Tonie Reincke, MD, medical director and owner of Reincke Vein Center in Sugar Land, Texas.

Common Local Causes (Usually One Leg)

When one leg swells up like a balloon and the other stays perfectly normal, it’s not just your body being dramatic. It’s a clue. Most often, it means the root cause is in the leg itself and not coming from an organ like your heart or kidneys.

1. Injury or Overuse

Stubbed toes, twisted ankles, pulled muscles … we’ve all been there. Trauma to the lower leg can trigger swelling. If the swelling is linked to pain, bruising, or limited motion, it’s likely due to a local injury.

2. Venous Insufficiency

Your leg veins are like one-way streets designed to carry blood back to the heart. When those valves get weak or damaged, blood can flow backwards and pool, says Dr. Reincke. That’s chronic venous insufficiency, and it often causes swelling, pain, cramping, or itching. You might also notice varicose veins or a heavy, aching feeling in the legs.

3. Deep Vein Thrombosis (DVT)

A deep vein thrombosis is a blood clot that forms in the deeper veins of the leg, usually on one side only, says Dr. Reincke. If you have sudden swelling, warmth, tenderness, or discoloration in one leg, especially if you’ve been sedentary (like after surgery or a long flight), get checked immediately. DVTs are serious because clots can travel to the lungs and cause a life-threatening artery blockage.

4. Lymphedema

Think of your lymphatic system like your body’s gutter system: It helps drain extra fluid out of tissues. When it’s blocked or damaged, that fluid starts backing up like a clogged drainpipe, leading to swelling that’s tough to shake, says Dr. Reincke. This can happen when lymph nodes are damaged or removed, often due to cancer treatment, infections, injury, or congenital conditions.

Lymphedema typically develops gradually into firm, non-pitting swelling, often affecting only one leg. Your skin may also become hard or thick, and you may experience a heavy, tight feeling in the affected leg.

5. Infection (Cellulitis)

If your leg is swollen, red, warm, and painful—especially with fever—you might be dealing with cellulitis, a bacterial skin infection. It usually affects one leg and requires prompt antibiotic treatment. Left untreated, cellulitis can spread quickly and lead to serious complications, including sepsis.

6. Baker’s Cyst

A Baker’s cyst isn’t something you pick up at the bakery. It’s a fluid-filled sac behind the knee that often forms due to arthritis or a knee injury. If the cyst ruptures, fluid leaks down into the calf and causes sudden swelling that can feel a lot like a DVT. You might also notice tightness when bending the knee or walking.

7. May-Thurner Syndrome

In May-Thurner syndrome, an artery in your pelvis presses against a nearby vein—kind of like stepping on a garden hose—which slows down blood flow from your leg. It’s a rare and lesser-known but potentially dangerous cause of single-leg swelling, especially on the left side.

That sluggish circulation can cause chronic swelling and raise your risk of a DVT. Treatment often involves placing a tiny stent inside the vein to restore blood flow, per Dr. Reincke.

While swelling in just one leg often points to a local cause, swelling in both legs usually signals an underlying systemic condition.

Systemic Causes (Often Both Legs/Feet)

When both legs are swollen, the issue is more likely coming from inside the body rather than the legs themselves. These are called systemic causes because they involve larger systems like the heart, kidneys, liver, or hormones. Let’s take a look at the most common culprits.

1. Heart Failure

When the heart can’t pump efficiently, blood backs up in the veins, pushing fluid into tissues. This is a hallmark of congestive heart failure, especially right-sided failure. Swelling often appears in both legs and ankles by evening and improves overnight. Other signs include shortness of breath, fatigue, and weight gain from fluid buildup.

2. Kidney Disease

Think of your kidneys as your body’s waste management crew. When they’re not keeping up, fluid starts piling up like garbage day got skipped, leading to puffier legs, ankles, and feet. You might also notice your urine looks foamy, and both of these symptoms are reasons to check in with your provider.

3. Liver Disease

Your liver makes proteins that keep fluid inside your blood vessels where it belongs. In conditions like cirrhosis, the liver’s ability to produce these proteins drops.

As a result, fluid starts leaking out into surrounding tissues and spaces, leading to swelling in your legs and feet, says Dr. Reincke. You may also notice a bloated, fluid-filled belly known as ascites.

4. Hypothyroidism

An underactive thyroid slows your metabolism and changes your balance of protein and fluids. The result: Non-pitting edema, aka fluid retention in the legs.

Unlike other causes, hypothyroid-related edema is usually non-pitting. You might also notice other telltale signs like unexplained weight gain, constant fatigue, dry skin, hair thinning, or cold intolerance.

5. Obstructive Sleep Apnea (OSA)

You wouldn’t think your nighttime breathing has anything to do with daytime leg swelling, but untreated sleep apnea can lead to persistent swelling in the legs, especially when paired with high blood pressure or fluid-retaining conditions like heart or kidney disease. During sleep, fluid that’s pooled in the legs during the day can shift upward toward the neck and chest. This fluid shift may worsen upper airway obstruction, contributing to more severe OSA symptoms.

6. Pregnancy

Your body’s doing something amazing—but growing a human can put serious pressure on your veins. While a bit of swelling is normal, sudden or severe swelling (particularly with headaches, vision changes, or high blood pressure) can be a sign of a hypertensive disorder called preeclampsia, a medical emergency. Mild, gradual swelling is common in late pregnancy due to increased blood volume and pressure on pelvic veins. Always report new swelling during pregnancy to your provider.

Medication-Related Swelling

Sometimes, the culprit behind your puffy ankles is hiding in plain sight: Your medicine cabinet. Certain prescriptions are known to stir up swelling, either by relaxing blood vessels a little too much, making your body cling to salt and water, or putting extra strain on your kidneys.

According to Dr. Reincke, common culprits include:

• Calcium channel blockers (like amlodipine)
• NSAIDs (like ibuprofen or naproxen)
• Steroids (like prednisone)
• Cancer therapies (like chemotherapy or immunotherapy)
• Hormonal therapies (like estrogen or testosterone)
• Diabetes medications (like thiazolidinediones)
• Antidepressants (like trazodone, mirtazapine, and escitalopram)

That said, don’t stop taking any medication on your own, even if you think it’s causing the swelling. Talk to your doctor first. There’s often a safer alternative or a simple tweak in the dose that can make a big difference.

When to Seek Care: Red Flags

Some types of leg swelling need urgent medical attention, says Dr. Reincke. Call your doctor or get immediate care if you notice:

• Sudden swelling in one leg with pain, warmth, or a change in color: This could be a sign of a DVT, and it requires fast treatment to prevent serious complications.
• Swelling with shortness of breath or chest pain: These symptoms could point to heart failure or a pulmonary embolism. Both can be life-threatening.
• Fever with red, tender, or hot skin: This may indicate cellulitis.
• Rapid weight gain with leg swelling and fatigue: This can be a clue that your body is holding on to fluid due to heart, kidney, or liver problems.
• Sores, ulcers, or weeping skin: These are symptoms often seen in advanced venous disease or lymphedema, and they can lead to infection and poor wound healing.
• A foot that becomes cool, numb, or pale: This could suggest reduced blood flow to the limb, possibly from a blocked artery, which requires immediate emergency evaluation
• Shortness of breath, chest pain, dizziness, or changes in vision or speech: These can be signs of a serious cardiovascular or neurological event. This is also recommended for emergency evaluation.

How Clinicians Diagnose the Cause

Think of diagnosing swollen legs like solving a medical mystery—it’s part detective work, part medical science. Your provider isn’t just glancing at your ankles and calling it a day. They’re gathering clues to get to the root of what’s really going on.

Questions to expect from a clinician about leg swelling

It all starts with the basics: a thorough conversation and hands-on exam. Your provider may ask things like:

• When did the swelling start, and how has it changed over time?
• Is it in one leg or both?
• Are there other symptoms?
• What medications are you taking?
• Have you traveled recently, had surgery, or a long period of immobility?

Depending on what they find, your provider may order certain tests to get a clearer picture:

• D-dimer blood test and leg vein ultrasound
• BNP blood test and possibly an echocardiogram
• Complete metabolic panel and urine test
• Venous reflux ultrasound in your legs
• Complete blood count test and wound culture
• Lymphatic imaging

Evidence-Based Treatments by Cause

There’s no magic fix for swollen legs (sorry, TikTok hacks won’t cut it). But there are proven treatments that actually work if you know what’s behind the swelling in the first place. Let’s break it down by cause.

Venous Insufficiency

Here are common treatments your doctor may recommend when blood pools in your legs from faulty veins:

• Compression stockings: These high socks gently squeeze your legs to push blood back toward your heart and reduce swelling.
• Leg elevation: Resting your leg above heart level helps fluid drain up and out.
• Weight management and exercise: Maintaining a healthy weight reduces strain on your veins, and regular walking or calf exercises keep blood moving.
• Avoiding prolonged standing: This precaution helps ease pressure on your veins, resulting in less swelling.
• Procedures like endovenous ablation or vein stripping: These minimally invasive treatments close or remove faulty veins so blood can reroute through healthier ones.

Deep Vein Thrombosis

A blood clot in a deep vein is serious and needs fast, careful management, including:

• Anticoagulation therapy (blood thinners like apixaban or warfarin): These medications prevent the clot from growing or moving.
• Monitoring for complications: Providers will watch for signs of clots moving to the lungs (like shortness of breath or chest pain).
• Guidance on physical activity: Gentle movement, such as walking, is usually encouraged to maintain circulation.

Lymphedema

With lymphedema, the goal is to keep things flowing and prevent flare-ups with the help of:

• Decongestive lymphedema therapy: This comprehensive approach combines massage, compression, skincare, and movement.
• Manual lymph drainage: Gentle massage helps move fluid out of swollen areas.
• Compression garments: These are worn long-term to manage daily swelling by supporting lymphatic and venous flow.
• Exercise: Light movement (like walking or stretching) keeps lymph fluid moving.

Infection (Cellulitis)

Early treatment is key to stopping cellulitis from spreading, including:

• Prompt antibiotics (oral or IV, depending on severity): These help stop the infection before it spreads.
• Rest and elevation: Keeping the swollen leg elevated can reduce inflammation and ease pressure.
• Monitoring for systemic spread: Be on the lookout for fever, chills, or red streaks—these may signal the infection is worsening.

Systemic Conditions (Heart, Kidney, Liver, Thyroid)

Here’s what to do if leg swelling is a symptom of an organ issue:

• Manage the underlying condition: Treatment may involve medications for heart failure, thyroid hormone replacement, or dialysis for kidney issues.
• Diuretics: These medications flush out excess fluid, but should only be used under the guidance of a doctor.
• Lifestyle changes: Cutting back on sodium, tracking fluid intake, and sticking to your medication plan can help reduce swelling.

Self care and lifestyle strategies for leg swelling

Injury or Overuse

When swelling follows a fall, workout, or strain, it’s often your body’s way of saying “take it easy.” Here’s what to do:

• RICE protocol (Rest, Ice, Compression, Elevation): This is the go-to method for easing swelling and discomfort in the first days after an injury.
• Physical therapy: Rehab exercises rebuild strength and mobility as you heal.
• Anti-inflammatory meds: Over-the-counter medications like ibuprofen may reduce pain and swelling.

Self-Care and Lifestyle Strategies

“Simple steps like leg elevation, regular walking, reducing salt, and staying hydrated can go a long way in preventing or relieving swelling,” says Dr. DePasquale.

Because sometimes the most powerful changes come from your daily routine. Here are some simple ways you can combat run-of-the-mill leg swelling in your day-to-day:

• Move regularly: Staying still is like inviting water to settle in your feet. Set a timer every hour to stand, stretch, or take a quick walk—your legs (and heart) will thank you.
• Ankle pumps and calf raises: Think of these as mini workouts for your vascular system. A few reps here and there keep the blood flowing—perfect for desk sessions, long drives, or flights.
• Leg elevation: Prop your legs up above heart level for 15 to 30 minutes, two to three times a day. This helps move fluid out of the lower legs and back into circulation.
• Watch your salt: A high-sodium diet can cause your body to hold onto excess fluid. Start reading food labels, cook at home when you can, and choose fresh foods over processed options to keep salt in check.
• Stay hydrated: Oddly enough, drinking water helps flush out excess fluid. Dehydration tricks your body into hanging on to water, so sip smart.
• Maintain a healthy weight: Extra body weight can put pressure on your veins and worsen swelling.
• Avoid smoking: Smoking stiffens blood vessels and slows down fluid return. The best thing you can inhale for your legs is just good old-fashioned air.
• Daily foot and skin checks: Check your legs and feet for cuts, sores, irritation, or changes in skin color (especially if you have diabetes or circulation issues). Catching these problems early can prevent complications.

Compression 101 (Use and Cautions)

Compression stockings can be a game-changing tool for managing lower-extremity edema. But compression isn’t one-size-fits-all, and it’s not for everyone, says Dr. DePasquale. If you have a history of peripheral artery disease (PAD) or poor circulation, compression stockings should only be used under medical supervision, as compression could actually make things worse. Here’s what to keep in mind:

• For mild symptoms: A light compression level of 10–20 mmHg is often enough for people with minor swelling or who are on their feet all day.
• For moderate to severe swelling: You may need 20–40 mmHg or stronger compression, but it’s important to talk with your doctor before using higher levels.
• Get the right fit: Compression only works if it fits properly. Too loose, and you won’t see benefits. Too tight, and you can cut off your circulation.
• Wear them consistently: Regular use is key for results. Ask your provider for the best plan for you.

Always check with your doctor before starting compression therapy, especially if you have numbness, tingling, or cold feet.

Prevention and Recurrence Reduction

Swelling that starts in your lower legs doesn't always stay put—it can creep into your daily life if you're not careful. The key? Stay one step ahead (literally and figuratively). These simple, proactive habits can help keep puffiness from making a comeback:

• Travel smart: Whether you're on a long flight or road trip, aim to move your legs at least once an hour. Light compression socks and plenty of water can also help offset the effects of sitting still for too long.
• Workplace ergonomics: Standing still is not your friend. So if your job involves long periods of inactivity, small adjustments can make a big difference. Alternate between sitting and standing if possible, and schedule short movement breaks throughout the day.
• Review medications regularly: Bring a full list of your medications to your healthcare provider and ask if any might be affecting your legs.
• Control chronic conditions: Managing underlying health issues can reduce the risk of complications like swelling.
• Catch it early: Notice your socks leaving deeper impressions or your shoes feeling tight by evening? That’s your body whispering, “Handle this now.” With a little rest, elevation, or compression, you might avoid a full-blown flare.

What Not to Do for Swollen Legs

Swollen legs aren’t just an “ignore it and hope for the best” situation. Some habits that seem harmless—or even helpful—can actually backfire. If your feet and ankles are puffing up, here’s what to avoid:

• Don’t ignore new or worsening symptoms: Sure, you can chalk it up to a long day on your feet. But sudden swelling (especially in just one leg) could mean a blood clot, infection, or another urgent issue. When in doubt, don’t tough it out—get checked.
• Don’t stay still for too long: Whether you're parked at a desk or on a long flight, prolonged sitting or standing lets gravity take over and encourages fluid to settle in your legs. Try to move every hour to keep things circulating.
• Don’t wear overly tight clothing: Skip the ultra-snug socks, leggings with a vice-grip waistband, or anything that leaves deep impressions on your skin. These don’t count as compression therapy; they’re just cutting off circulation.
• Don’t self-prescribe compression stockings: On that note, while compression socks can be helpful, they’re not right for everyone. If you have circulation issues or conditions like peripheral artery disease, the wrong compression can actually worsen symptoms. Always check with your doctor first.
• Don’t go overboard on salt: Salty snacks and processed foods might be convenient, but too much sodium causes your body to retain fluid. A high-sodium diet can be a major contributor to preventable swelling.

The Takeaway

• Swelling from the knee down is often caused by fluid buildup, which may stem from minor issues like standing too long or more serious problems like blood clots, heart failure, or kidney disease.
• One-sided swelling usually points to a local issue (like injury, DVT, or infection), while swelling in both legs is more often due to systemic conditions or medications.
• Red flag symptoms—like sudden swelling, chest pain, shortness of breath, or fever—require prompt medical attention to rule out life-threatening causes such as blood clots or infections.
• Diagnosis involves a detailed history, physical exam, and targeted tests (such as ultrasounds or blood work) to pinpoint the underlying cause of leg swelling.
• Treatment is tailored to the cause, but may include compression therapy, medications, lifestyle changes, and procedures to improve circulation or drain fluid.
• Simple daily habits—like walking regularly, elevating your legs, limiting salt, and staying hydrated—can significantly reduce or prevent leg swelling for many people.

Frequently Asked Questions (FAQs)

What helps swollen legs from the knee down?

It depends on the cause, but some tried-and-true strategies include elevating your legs, wearing compression stockings (if appropriate), staying active with walking or calf exercises, and reducing salt intake. If the swelling is due to a specific condition like venous insufficiency, heart failure, or lymphedema, targeted treatments like diuretics, decongestive therapy, or vein procedures may be recommended by your provider.

Which organ causes leg swelling?

Several organs can be involved. The heart, kidneys, and liver are the big three when it comes to systemic (whole-body) fluid balance, but the thyroid and lymphatic system can also play roles. When these organs or systems aren’t functioning well, fluid tends to build up—often showing up first as swelling in the lower legs.

When should you go to the hospital for swollen feet and legs?

Call your doctor or head to the ER if you experience:

• Sudden one-leg swelling with pain or warmth
• Swelling with chest pain or shortness of breath
• Fever with red, hot, or painful skin
• Rapid weight gain, fatigue, or fluid buildup
• Cool, numb, or pale feet
• Dizziness or changes in vision or speech

Which leg swells with congestive heart failure?

That’s something of a trick question: It’s both! Both the right and left legs typically swell with congestive heart failure, especially by the end of the day. The swelling usually improves overnight when you’re lying down. This is because heart failure causes fluid to back up into the veins, leading to bilateral leg and ankle edema.

How to reduce swelling in the feet during pregnancy?

Mild swelling is common during pregnancy. To manage it:

• Elevate your feet above heart level a few times a day
• Stay well-hydrated
• Limit sodium intake
• Wear comfortable shoes and light compression socks (if approved by your doctor)

However, if the swelling is sudden or severe—especially if it comes with headaches, vision changes, or high blood pressure—it could be a sign of preeclampsia, which requires immediate medical attention.

If you’re unsure what’s behind your swelling, a quick medical evaluation can provide peace of mind and keep you safe.

General Medicine follows a strict editorial process, including using real experts to write our articles, vetted primary sources, fact-checking, a secondary medical review, and updates as necessary. This article was medically reviewed and fact checked by Swapna Ghanta, MD, and Ecler Ercole Jaqua, MD.