Kristen Gasnick, PT, DPT, is a medical writer and a physical therapist at Holy Name Medical Center in New Jersey.

Oluseun Olufade, MD, is a board-certified orthopedist. He teaches as an Assistant Professor of Orthopedics at Emory School of Medicine in Atlanta, Georgia.

Many different conditions can cause lower back pain or swelling in the legs and feet, but not as many conditions cause both.

Swelling in the legs and feet is caused by edema (swelling) and/or inflammation. Some conditions that can cause both lower back pain and swelling are not serious and can be treated at home, while others demand medical attention.

This article will explain conditions that can cause both lower back pain and swelling in the legs and feet, and how to diagnose and treat them.

Some conditions that cause swelling in the the legs and feet from edema, as well as low back pain, include varicose veins, kidney disease, and pregnancy.

Varicose veins, also called spider veins, are enlarged, twisted veins that mostly occur in the lower legs. Varicose veins result from increased blood pressure and weakening of blood vessel walls and valves of the affected veins. They are more common in people of older age, female sex, and those with a family history of chronic venous insufficiency.

Varicose veins are also more likely to develop after prolonged standing and with other conditions such as obesity, pregnancy, chronic constipation, or tumors. Varicose veins often cause leg aches and pains, and swelling in the feet and legs, from insufficient blood flow from the legs back to the heart.

While varicose veins do not directly cause lower back pain, it can develop from conditions like obesity and pregnancy that increase the risk of developing varicose veins.

Kidney disease and resulting renal (kidney) failure can cause pain in the lower back below the rib cage and at the sides of the body. Renal conditions that affect kidney function also cause edema in the legs and feet due to increased sodium and fluid retention because the kidneys cannot properly filter out sodium from the blood.

Back pain commonly occurs with pregnancy due to the increased strain that the developing baby and associated weight gain places on the lumbar spine. The developing baby within the uterus also stretches the abdominal muscles, which weakens their ability to provide support. Altered pregnancy hormones also increase the laxity of ligaments, which can further weaken the stability of the lumbar spine, leading to lower back pain.

Swelling in the legs and feet can occur during pregnancy from increased fluid accumulation. To accommodate the growth and development of a baby, the body’s blood plasma volume will increase by 30% to 50%. This increase in blood volume consequently causes excess fluid to accumulate in the body, especially in the legs and feet due to the distance away from the heart.

Conditions like arthritis, sciatica, ankylosing spondylitis, piriformis syndrome, arachnoiditis, and infection can cause lower back pain and swelling in the legs and feet from inflammation.

Arthritis, including rheumatoid arthritis and osteoarthritis , is an inflammatory condition that can affect multiple joints of the body, including the spine, hips, and knees. Symptoms of arthritis include joint pain, stiffness, inflammation, and swelling. Arthritis can cause lower back pain while simultaneously resulting in knee, lower leg, and ankle swelling if the joints of the legs including the hips and knees are also affected and inflamed.

Sciatica produces pain in the lower back and down the legs from compression of the sciatic nerve. Other symptoms that can result from sciatic nerve compression or irritation include numbness, tingling, and swelling in the legs.

Ankylosing spondylitis is a chronic inflammatory form of arthritis that most commonly affects the back and neck, resulting in neck and lower back pain, stiffness, fever, and fatigue. Ankylosing spondylitis can also affect tendons and ligaments, especially the Achilles tendon and plantar fascia, which can cause inflammation and swelling around the feet and ankles.

Piriformis syndrome is a condition caused by irritation, spasm, or injury to the deep piriformis muscle of the back of the hip, causing sciatic nerve irritation and resulting pain, numbness and tingling down the affected leg. Piriformis syndrome can also cause pain in the lower back as well as swelling in the affected leg.

Arachnoiditis is a condition that results from inflammation of the arachnoid layer, one of three membranes that surround and protect the brain and spinal cord. The arachnoid layer can become inflamed from a bacterial or viral infection, direct injury to the spine, chronic nerve compression, irritating chemicals, or complications from spinal surgeries and procedures.

Symptoms of arachnoiditis include chronic lower back and leg pain, numbness, tingling, burning, muscle cramping and spasms, and altered bladder, bowel, and sexual function. Weakness, paralysis, and swelling in the lower limbs may also occur.

Infections can affect multiple parts of the body and cause a variety of symptoms. Cellulitis is a frequently occurring bacterial skin infection that affects the legs, resulting in pain, tenderness,  redness, warmth, and swelling.

If cellulitis progresses, it can also cause osteomyelitis (a bone infection) that can cause lower back pain, and meningitis (inflammation of the membranes that surround the brain and spinal cord), which can cause back and leg pain, weakness, fever, headaches, fatigue, nausea, vomiting, and other neurological symptoms.

The source of your lower back pain will help guide your treatment options. These include:

Swelling in the legs and feet can result from a variety of different causes so treatment will vary. Treating any underlying condition is necessary first before attempting other treatments, which include:

Back pain and swelling in the feet and legs that have not improved after one month warrants a visit with your healthcare provider to help determine the underlying cause. Having both symptoms at the same time without an injury to either your back, legs, or feet may indicate an underlying condition that needs to be treated. 

If you exhibit significant pain, redness, warmth, and swelling in your legs, or experience fever, chills, nausea, vomiting, or diarrhea, you should seek immediate medical attention as these are signs of an infection.

Lower back pain and swelling in the legs and feet are common symptoms, but they occur less frequently together. Causes of both symptoms concurrently include varicose veins, pregnancy, kidney disease, arthritis, ankylosing spondylitis, arachnoiditis, systemic infections, and sciatic nerve compression from piriformis syndrome. 

Treating the underlying causes of lower back pain and swelling in the legs and feet comes first, often through medication, followed by symptom management including stretches, core strengthening, weight loss, heat, and ice to alleviate lower back pain, and compression stockings, leg elevation, exercise, and fluid and sodium regulation to alleviate leg and feet swelling.

If you have been experiencing symptoms for more than one month without any improvement, make sure you see a medical professional to determine the underlying cause and receive appropriate treatment.

Some conditions that affect the back can also result in swelling in the legs if the blood vessels and/or nerves traveling from the back to the legs are impacted.

You should go to the hospital immediately if you exhibit significant pain, redness, warmth, and swelling in your legs, or experience fever, chills, nausea, vomiting, or diarrhea. These are signs that an infection is likely present.

Back pain and general body aches are among the most frequently reported symptoms of COVID-19. Swelling and redness in the toes and feet have also been reported. 

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Soi V, Yee J. Sodium homeostasis in chronic kidney disease. Adv Chronic Kidney Dis. 2017;24(5):325-331. doi:10.1053/j.ackd.2017.08.001. 

The American College of Obstetricians and Gynecologists. Back pain during pregnancy.

Vricella LK. Emerging understanding and measurement of plasma volume expansion in pregnancy. Am J Clin Nutr. 2017;106(Suppl 6):1620S-1625S. doi:10.3945/ajcn.117.155903

Jankovic D, Peng P, van Zundert A. Brief review: piriformis syndrome: etiology, diagnosis, and management. Can J Anaesth. 2013;60(10):1003-1012. doi: 10.1007/s12630-013-0009-5. 

National Institute of Neurological Disorders and Stroke. Arachnoiditis information page.

Centers for Disease Control and Prevention. Cellulitis: all you need to know.

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