Edema is swelling caused by fluid trapped in your tissues. It’s most common in the legs but can affect any part of the body, like swollen ankles from varicose veins or hand edema from trauma.
Lower extremity edema is often experienced in both legs. It is typically caused by systemic medical conditions such as congestive heart failure, heart valve disorders, poor kidney function, too much salt intake, or obesity. However, sometimes people may have swelling in one leg. Let’s examine what causes swelling in one leg only, how it’s diagnosed, and available treatment options.
Common Causes of Single-Leg Swelling
Someone may have only one leg swollen while the other one looks perfectly normal for many reasons, but the mechanism is generally the same.[1]
If your veins are compressed or are otherwise damaged and impaired, it is harder to circulate blood. This pressure can lead to overstretched veins, making you more susceptible to malfunctioning valves.
When this happens, the blood can’t efficiently move upstream, so it’s likely to pool and cause venous reflux and swelling.
Medical Conditions Associated with Single-Leg Swelling
A DVT occurs when there’s a blood clot in a deep vein, typically in the leg. The clot obstructs normal blood flow, increasing pressure and fluid in surrounding tissues.
Significant swelling in the leg ensues, which generally involves the entire lower extremity where the clot occurs. In addition to swelling, a DVT can be painful. You’ll likely feel heaviness and tenderness in the leg, which can also feel warm to the touch. [2]
There is a higher chance of DVT after prolonged immobility, travel, surgery, etc. If you suspect this, you should immediately seek medical attention and have a venous ultrasound scan. If you are diagnosed with a DVT, you will be prescribed a blood thinner to dissolve the clot.
Injury or Trauma
Think about the last time you injured one of your limbs. It probably led to pain, redness, bruising, and swelling, at least while it healed. When you have significant trauma to the leg (like sprains or fractures), it damages blood vessels and soft tissues in a way that makes fluid leak into areas around the injury site. This causes swelling.[2] You’ll notice even more inflammation as the body sends immune cells and blood flow to the area. The swelling will go down over time as the injury heals.
Infection
A common leg infection is cellulitis, which refers to an infection of the subcutaneous tissue. This happens when bacteria enter your skin and cause an inflammatory response, triggering more blood flow, immune cells, and fluid buildup in the infected area. This activity leads to swelling paired with pain, warmth, and redness.[2 Infections are typically treated with antibiotics.
Lymphedema
Your lymphatic system is a network of vessels through which lymph drains from your tissues into your blood. Lymphedema occurs when this drainage system isn’t working correctly.
It can occur after lymph nodes are removed or damaged, preventing proper lymphatic fluid flow and causing the impacted leg to swell. It can also occur after surgery, infection, trauma, or cancer. If not treated, lymphedema can cause heaviness in the leg, skin changes, ulcers, and an increased risk of infection that can be debilitating.[2]
Compression therapy, physical therapy, lymphedema pumps, and massage therapy can help decrease swelling in the leg.
Venous Insufficiency
Venous insufficiency occurs when leg vein valves aren’t working properly to return blood to your heart. This causes blood to pool in your lower extremities where it’s not supposed to be, it increases pressure in your veins, leaking fluid into nearby tissues and causing swelling in the leg.[1][2]
This swelling can worsen if you sit or stand for long periods or lead a sedentary lifestyle. If venous insufficiency isn’t managed, it can cause additional problems, like swelling, skin discoloration, enlarged painful varicose veins, and in some cases, wounds or ulcers.
May-Thurner Syndrome
May-Thurner Syndrome happens when your right iliac artery (which carries blood to the right lower leg) compresses the left iliac vein (which carries blood from your left leg back to your heart), restricting blood flow, which can lead to one-sided left leg swelling.
This pressure causes blood to pool and fluid to build up in the leg, which could result in swelling, pain, and blood clots.[3]
This syndrome can be diagnosed with a CT scan. If Indicated, the compressed vein can be opened with placement of a venous stent during an outpatient minimally invasive procedure called a venogram. Relieving this obstruction can bring significant improvement in the leg swelling quickly after the procedure.
Certain Cancers
Certain types of cancer can lead to swelling in one leg only by blocking lymphatic or venous drainage — particularly if there’s a tumor or metastatic cancer cells in the way. Cancers may compress nearby blood vessels or lymph nodes, making it harder for blood and fluid to circulate normally and cause swelling.
It’s also possible for cancer treatments, like radiation or surgeries, to promote leg swelling by damaging lymphatic vessels or veins.[2]
Arthritis
Arthritis is the inflammation of joints. It can cause swelling in one leg when inflammation triggers an increase in fluid in tissues surrounding the affected leg. Arthritis can make it harder to move around as it is, which can be worsened when leg swelling is involved.[4]
Diagnosing the Cause of Swelling in One Leg
Diagnosing the cause of swelling in one leg requires a physical exam and evaluation of your medical history by a licensed healthcare provider. They will ask questions about the onset of the swelling and the symptoms you’re experiencing, followed by a series of diagnostic tests.[5][6]
Common tools used to understand what causes swelling in one leg only include blood tests, MRI, or ultrasound imaging, as these can help identify root causes like tumors, infections, or DVTs.
Treatment Options for Swelling in One Leg
When you have a single swollen leg, it’s important to take it seriously, get it checked out, and start the recommended treatment. The appropriate treatment depends on your symptoms and root cause.[7]
Some of the commonly prescribed treatments to help reduce swelling in one leg include:
- Managing Underlying Conditions: If you have venous insufficiency or lymphedema, for instance, your vascular specialist will review your diagnosis and can formulate a treatment plan to improve your symptoms.
- Elevation: Elevating your affected leg above your heart periodically can help alleviate swelling by redirecting fluid away from the area.
- Compression Therapy: Compression stockings can be very effective in applying light pressure and reducing swelling. These are especially helpful for people who sit or stand for prolonged periods or during travel.[8]
- Exercise: Moving your body improves circulation and helps reduce swelling. Try low-impact movements like walking, swimming, or biking.
- Nutrition: What you’re eating is important for all aspects of health, including circulatory issues and swelling. Prioritize minimally processed foods like fruits, vegetables, whole grains, nuts, seeds, legumes, and other lean proteins while reducing added salt and sugar that can make inflammation and swelling worse.[9][10]
When to Seek Medical Attention
If you’re experiencing swelling in one of your legs that isn’t going away or is getting worse, it’s time for medical attention. Early intervention is key to understanding what causes legs to swell and addressing yours safely and effectively.
Our team at Empire Vein and Vascular Specialists is ready to help you figure out what causes one leg to swell and more. Contact us at 1-800-VARICOSE or send us a message to schedule a consultation today.
Sources
- Scherer K, Khilnani N. Evaluation and Management of Patients with Leg Swelling: Therapeutic Options for Venous Disease and Lymphedema. Semin Intervent Radiol. 2021;38(2):189-193. doi:10.1055/s-0041-1727162
- Gasparis AP, Kim PS, Dean SM, Khilnani NM, Labropoulos N. Diagnostic approach to lower limb edema. Phlebology. 2020;35(9):650-655. doi:10.1177/0268355520938283
- Badawy E, Seif MA, Elmoheen A. May-Thurner Syndrome: A Neglected Cause of Unilateral Leg Swelling. Open Access Emerg Med. 2020;12:121-125. Published 2020 May 1. doi:10.2147/OAEM.S246018
- Poudel P, Goyal A, Lappin SL. Inflammatory Arthritis. [Updated 2023 Apr 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507704/
- Mutluer FO, İndelen C, Dinçer N, Aslan G, Ateş MŞ. Unilateral leg edema: Is it always vascular?. Turk Kardiyol Dern Ars. 2018;46(8):706-709. doi:10.5543/tkda.2018.85601
- Gasparis, A. P., Kim, P. S., Dean, S. M., Khilnani, N. M., & Labropoulos, N. (2020). Diagnostic approach to lower limb edema. Phlebology. https://doi.org/10.1177/0268355520938283
- Scherer K, Khilnani N. Evaluation and Management of Patients with Leg Swelling: Therapeutic Options for Venous Disease and Lymphedema. Semin Intervent Radiol. 2021;38(2):189-193. doi:10.1055/s-0041-1727162
- Kolluri R. Compression therapy for treatment of venous disease and limb swelling. Curr Treat Options Cardiovasc Med. 2011;13(2):169-178. doi:10.1007/s11936-011-0114-0
- Lent-Schochet D, Jialal I. Physiology, Edema. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537065/
- Ma X, Nan F, Liang H, et al. Excessive intake of sugar: An accomplice of inflammation. Front Immunol. 2022;13:988481. Published 2022 Aug 31. doi:10.3389/fimmu.2022.988481