What causes of swollen feet and ankles?

What causes of swollen feet and ankles?

The below list explains some of the most common causes of swollen feet and ankles (i.e. oedema in these areas): 

Lymphedema (lymph node drainage blockage)

This condition refers to an accumulation of lymphatic fluid in the tissues of the body that may develop as a result of issues with the lymph vessels wherein a blockage occurs, or if lymph nodes have been surgically removed. The disorder commonly affects the limbs and may cause swelling in one or both legs, ankles and feet.

The lymphatic system has a number of interrelated functions including maintaining fluid balance (homeostasis) within the body, combatting infection and the absorption of fats.  

This system drains excess tissue fluid (known as interstitial fluid) and returns it to the blood. This is vital in the maintenance of fluid balance as the body’s blood capillaries release small amounts of blood plasma and fluid into the surrounding tissues and without lymph drainage occurring, these fluids accumulate within the tissues and swelling (oedema/edema) occurs.

The fluid formed during the process of drainage is called lymph fluid. This fluid contains white blood cells (lymphocytes – B cells and T cells), chyle (fluid from the lymphatic vessels of the small intestines) and red blood cells as well as a concentration of foreign substances (antigens) and infectious agents (bacteria, viruses and fungi) when these are present in the body.

Lymph fluid travels along a complex network of lymph capillaries and vessels, similar to the circulatory system's capillaries and veins. These vessels are connected to the lymph nodes, here, the fluid will be filtered, and any unwanted substances trapped and destroyed.

When harmful invaders such as bacteria, fungi or viruses are detected in the lymph fluid, the lymph nodes create more white blood cells to fight off any potential infections, this may result in swelling of the lymph nodes (also referred to as ‘swollen glands’) as they go into overproduction of fluid. This swelling can be felt under the arms, above the collarbone, in the neck and groin and is often the first sign that the body is fighting infection.

The body has hundreds of lymph nodes, they are located deep inside, around the heart and lungs while some are situated closer to the skin’s surface such as under the arms or in the groin. The movement of the body’s skeletal and smooth muscles, as well as respiratory action, acts as a pump for moving lymph fluid through the lymph channels and back into the circulatory system.

If there is an issue with the lymph nodes or lymphatic system due to an infection or other health issues leading to lymph node removal (some cancer patients may have to have their lymph nodes removed should cancer spread to these tissues), the lymph fluid’s movement may be blocked. If lymph fluid that accumulates is left untreated, this can impair the body’s ability to heal wounds and lead to swelling and further infection. The fingers and toes may also swell as a result of circulatory issues with the lymph fluid.

If you have ever undergone treatment for cancer (recent or otherwise) and experience swelling of your lymph nodes, then it is advised that you see your doctor immediately. 

Another cause of lymphedema is an infection caused by a parasite of the filariidae species family. The condition is called filariasis and is usually characterised by unilateral swelling of the legs (i.e. only one of the legs swells) resembling the size and shape of an elephant’s leg, hence the swelling may be referred as elephantitis. The condition occurs due to the infection causing damage to the lymphatic system resulting in the malfunctioning of its drainage system.

Swollen feet and ankles in pregnancy and due to pregnancy complications

Feet and ankle swelling is common in pregnancy. Most women tend to start experiencing this type of swelling during their fifth month of pregnancy, however, the symptom can occur at any stage and tends to progress during the third trimester as the womb grows.


The reason for this is that by week 32 of pregnancy the body produces almost fifty percent more blood than normal to aid in supporting the developing foetus. This can put strain on the circulatory system and may result in fluid retention and swelling (oedema) of the hands, legs, feet, ankles and face. Changes in blood chemistry also shift more fluid into the body’s tissues.

Swelling may become more pronounced in the feet and legs too as the growing uterus takes up more space in the abdomen, increasing pressure on the veins of the legs and pelvis, hindering blood flow back to the heart and causing further fluid retention below the knees. This is usually exacerbated on hot summer days, when a pregnant woman has been on her feet for extended periods as gravity causes fluid to pool in the lower extremities and occasionally due to excessive caffeine or sodium intake.

While mild oedema is to be expected during pregnancy, should swelling move up the calf (leaving an indentation when light pressure is applied, known as ‘pitting oedema’) and be accompanied by discolouration of the legs or if it rapidly develops in the face or hands in the third trimester, this may be a warning sign of a condition known as pre-eclampsia (formerly referred to as toxaemia).  

Pre-eclampsia is a severe condition that typically develops after week 20 of pregnancy. The condition is characterised by high blood pressure, also known as hypertension, and protein in the urine, known as proteinuria. High blood pressure may occur even if there have never been any issues with it in the past.

While the exact cause of preeclampsia is unknown, it is thought to be the result of poor oxygen flow to the placenta due to issues with its development and function. As a result, the problematic placenta releases certain substances, one of these is a protein that may cause damage to the placental and endothelial cells. Endothelial cells are specialised cells that line the blood vessels.

Oedema occurs as a result of preeclampsia due to elevated blood pressure within the blood vessels and resulting damage to endothelial tissues causing the fluid in the blood vessels to flow into the surrounding tissues.

Some of the other, more notable early signs and symptoms of this condition include:

  • Visual issues (blurre vision and seeing flashing lights)
  • Pain experienced just below the ribcage in the centre of the abdomen above the navel (an area called the epigastrium)
  • Severe headache
  • Infrequent urination
  • Nausea
  • Vomiting

It is advised that you make an appointment with your doctor or gynaecologist if you are pregnant and notice sudden and/or severe swelling accompanied by any of the above symptoms during pregnancy.

Ankle or foot injury

If you have suffered an injury to your ankle or foot this may result in swelling. This form of swelling is commonly seen in people who participate in sports such as dancing, field sports or running. The most common injury to result in oedema is a sprained ankle. This may occur due to a misstep or impact which causes the ligaments (fibrous bands of tissue connecting the bones together at the joints) that are responsible for holding the ankle in place to stretch past their usual range of motion, resulting in a tear and damage to the ankle.

Sprained ankle

A fracture to the foot or ankle may also cause significant swelling of the affected area/s.

Oedema resulting from ankle and foot injuries is due to the blood vessels dilating in order to allow fluid to move into and accumulate within the soft tissue that surrounds the affected area as the body attempts to heal the trauma that has been sustained. Blood flow is increased and certain white blood cells (known as leukocytes) will also be moved into the affected area, resulting in inflammation. Warmth and redness are caused by the increase in blood flow and associated inflammation, and bruising around the torn ligaments may also occur. Bruises are manifestations of blood forming under the skin.

If you want to reduce the swelling caused by these types of injuries, elevating your leg on a pillow or stool immediately after the trauma occurs can help to prevent blood flow to the area and the progression of swelling.  It is best to avoid walking or putting pressure on the affected foot or ankle and using ice packs and possibly wrapping the ankle or foot with a compression bandage may also be helpful.

Venous insufficiency

In some cases, swollen feet and ankles are a result of a condition known as venous insufficiency. This refers to a disorder wherein the blood struggles to move from the veins in the feet and legs to the heart.

Blood in vein

Normally, the one-way valves in the veins will ensure that blood is constantly moving back to the heart. In order to do this, blood will have to flow upward (against gravity) from the veins of the legs. The muscles of the feet and calves contract and squeeze the veins with each step, acting as a lever and assisting in this process.

If the one-way valves have been damaged due to a vein disorder, such as varicose veins or blood clots, then this may lead to venous insufficiency. As a result of the damage, blood reaching the valves may leak back down the vessels and fluid will accumulate in the soft tissues of the feet, ankles and legs. This pooling of blood, or rather, a collection of blood is known as stasis. CVI (chronic venous insufficiency) can lead to skin ulcers, skin changes like hyperpigmentation or discolouration, a rash (called stasis dermatitis), and infection which may exacerbate swelling.

Infection (Cellulitis)

Cellulitis, a common bacterial infection of the skin, can affect any portion of the body but commonly manifests in one of the lower legs and results in redness and swelling. The affected area will be swollen and painful and the infection is able to spread rapidly to other parts of the body.

The infection is usually caused by Streptococcus (groups B, C and G) and occasionally by Staphylococcus (S. aureus) bacteria. Cellulitis occurs when one of these strains of bacteria enter the skin through a crack or cut, including those due to insect bites and surgical incisions. Chronic eczema and psoriasis may also lead to the development of this condition.

Below are some of the symptoms of cellulitis:

  • A rash or skin sore that develops rapidly
  •  A warm feeling around the affected area
  • Inflammation and redness of the skin
  • Swelling (oedema/edema)
  • Tenderness and pain in the affected area
  • Fever
  • Leakage of clear, yellow fluid or pus

If you think you may have cellulitis, make an appointment with your doctor as soon as possible.

Peripheral oedema and diabetic neuropathy

Various treatments for diabetes such as insulin can result in oedema of the legs and feet. Mild swelling from insulin is commonly seen in a number of individuals beginning treatment for diabetes, this will generally resolve on its own within a few weeks.

Diabetes can also result in a condition known as diabetic neuropathy. This is a type of nerve damage that may occur as a result of prolonged, long term hyperglycaemia, which refers to the exposure to high blood glucose (sugar) levels) in type 1 diabetes and in type 2 diabetes, causing damage to the nerve fibres of the lower extremities which results in oedema.

High blood glucose inhibits the ability of the nerve fibres to transmit messages. It also weakens the walls of capillaries (small blood vessels) that supply the nerves with nutrients and oxygen. Oedema then results from this interference and damage as fluid begins to accumulate.

Infection forming under foot

If you have diabetes, it is advised that you keep an eye out for sores and/or blisters on your feet, as nerve damage may blunt pain sensations and cause foot issues to progress. If you notice a sore or blister that seems infected, then make an appointment to see your doctor.

Blood clots

Your blood flows through arteries, veins and capillaries, also known as blood vessels. As long as your heart is always beating, your blood will be flowing and is pumped by the heart into the different glands, cells and organs of the body. After reaching these points, your blood will then return back to the heart via valves in the veins and the contraction of the skeletal muscles which act as a pump, squeezing the blood through your veins and back to the heart.

Blood clots may form if you are immobile for extended periods (either during long journeys or due to health reasons that require bed rest) and your muscles are not regularly contracting to squeeze and push the blood back to your heart. When blood becomes stagnant it will begin to form small clots on the walls of veins. An initial clot may grow gradually to either partially or completely block a vein, thus, preventing blood from returning to the heart. Blood clotting in a vein is known as venous thrombosis.

If blood clots develop in the vein of your leg, this can stop blood from returning to your heart, resulting in the swelling of the foot and ankle. Blood clots may be superficial, meaning they occur just beneath your skin, or they can be deep within the body, this is known as deep vein thrombosis (DVT). Deep clots can block one or more of the major veins in your legs. If this occurs, the clots have the potential to be life-threatening should they move and travel to your lungs or heart.

If you experience swelling in one of your legs, accompanied by fever, pain and/or a change in the colour of the affected leg, then you should call your doctor immediately or head to the nearest emergency room.

Heart, kidney or liver disease

Heart failure

In some cases, swelling in the feet and ankles may be a sign of an issue relating to heart or kidney or liver disease. If you notice swelling in your ankles in the evenings and you have not been on your feet for an extended period, this may be due to water and salt retention as a result of right-sided heart failure.

Heart failure generally begins on the left side of the heart as the left ventricle is unable to efficiently pump blood. This creates a build-up of pressure within the left side of the heart, which will eventually cause the right side to fail. In heart failure, the heart’s main pumping chambers, known as the ventricles, may stiffen or not fill with enough blood between beats.

Some cases of heart failure may occur due to damage or weakening of the heart, this causes the ventricles to dilate to a point where the heart is unable to keep up with the demands of the body to function. Both left-sided and right-sided heart failure may result in fluid building up in the legs, with right-sided failure resulting in notable swelling of the legs, ankles and feet.

Kidney disease

Swollen feet and ankles are also a sign of chronic kidney disease (CKD). CKD refers to a condition wherein the kidneys no longer function as well as they should. There are several conditions that can lead to the kidneys becoming diseased or damaged, some of these include diabetes, hypertension (high blood pressure) or ageing, as advanced age may affect the strength and capabilities of the kidneys.

The main functions of your kidneys are as follows:

  • Filtering out any waste material from your bloodstream, this is then passed out of the body in your urine.
  • Controlling the body’s water balance.
  • Aiding in the control of blood pressure, this is partly done by regulating the amount of water and sodium that is passed out in your urine (which influences blood volume), and partly through the production of renin, a hormone which elevates blood pressure.
  • Producing a hormone known as erythropoietin, this stimulates bone marrow to produce red blood cells, aiding in the prevention of anaemia.
  • Aiding in maintaining the chemical balance of the blood and regulating calcium, potassium and sodium levels.
  • Activating vitamin D.

If these functions are impaired as a result of chronic kidney disease or damage, this can result in fluid retention in your lower legs, causing swollen feet and ankles.

Liver disease

If you have liver disease then this may affect your liver’s production of albumin, a specialised protein that plays a vital role in fluid balance and prevents blood from leaking from blood vessels into the surrounding tissues. If there are inadequate amounts of this protein, this may result in fluid leakage which leads to swelling.

Liver disease

Swelling of the legs is generally a more severe symptom of advanced liver disease, known as cirrhosis. This is a condition, which occurs during the later stages of liver disease, is characterised by scarring of the liver due to chronic infections (hepatitis B and C) or autoimmune liver disease, chronic alcoholism and a variety of other health conditions.

Cirrhosis is the result of the liver’s attempts to heal itself from damage which causes scar tissue to form. The more scar tissue present, the more difficult it is for the liver to function correctly. If you notice swelling in your legs accompanied by some of the below symptoms, then speak to your doctor immediately:

  • Fatigue
  • Bruising easily
  • Bleeding easily
  • Itchy sin
  • Jaundice (yellowing of the eyes and skin)
  • Swelling of the abdomen
  • Nausea
  • Vomiting
  • Weight loss

Side effects of medications

There are a number of different drugs that can result in swollen feet and ankles as a side effect of their use. Some of these include:

  • Those containing hormones such as oestrogen which is found in hormone replacement therapy and contraceptives, as well as testosterone.
  • Some types of medications for blood pressure known as calcium channel blockers, which include:
    • Amlodipine (Norvasc)
    • Nifedipine (Afeditab Adalat, Nifedical, Procardia, Nifediac)
    • Verapamil (Isoptin SR, Covera-HS, Isoptin, Calan, Verelan)
    • Diltiazem (Cartia, Dilacor, Cardizem, Diltia, Tiazac)
    • Felodipine (Plendil)
  • Steroids which are used in the treatment of inflammatory conditions, some examples of these drugs include:
    • Anabolic steroids
    • Corticosteroids (Prednisone)
  • Antidepressants which include a group of drugs known as tricyclics, some of these are mentioned below:
    • Amitriptyline (Endep, Elavil, Vanatrip)
    • Nortriptyline (Aventyl, Pamelor)
    • Desipramine (Norpramin)
    • MAO (monoamine oxidase) inhibitors which include tranylcypromine (Parnate) and phenelzine(Nardil) – These are not as commonly used as these medications were first introduced during the 1950s to treat depression and have since then been replaced by more advanced options.
  • NSAIDs (Non-steroidal anti-inflammatory drugs) – These aid in reducing pain and decreasing fever and inflammation when used in higher doses.
  • Diabetes medications used to treat issues with blood sugar levels and include drugs such as:
    • Insulin
    • Byetta
    • Actos
    • Metformin
    • Januvia
    • Victoza

Before prescribing any medication, your doctor is likely to inform you of the potential side effects (should they feel this is warranted). If you suspect that swollen feet and ankles are a side effect of a drug you are currently taking, then speak to your doctor about this as soon as possible.

In most cases, the benefits of the above-mentioned drugs outweigh the side effect of mild swelling, however, should swelling become more severe or cause pain, then it is best to chat to your doctor about swopping medications. Never change or discontinue prescribed medications without your doctor’s explicit consent.

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