Legs may swell for numerous reasons. Some of the possible diagnoses are listed in this leaflet.
Types of swollen legs
There are many different kinds of swelling of the legs. One leg or both legs could be swollen. If both legs, it could be symmetrical or worse on one side. A specific part of the leg(s) could be swollen, or the entire leg(s). It could have come on suddenly or gradually. It could be there all the time, or it could come and go. It could be painful nor not. Taking into account all these things will help narrow down the likely cause.
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Where could the swelling be coming from?
Most often the swelling comes from fluid in the spaces between the cells in the legs. When this is the case it is called oedema. It is called pitting oedema if a dent made when you press with your fingertip stays in the skin after you have taken the fingertip away.
By James Heilman, MD, CC BY-SA 3.0 , via Wikimedia Commons
The swelling could also be coming from skin, bones, tendons - from any tissue of the leg.
See also the separate leaflet called Oedema (Swelling) for further information.
What causes swollen legs?
The most common cause of swollen legs is oedema. This is a collection of fluid in between the cells, which are the building blocks of the tissues of our body. Oedema can occur in one particular part of the body, or it can be generalised. If generalised, gravity takes the fluid to the part of you which is hanging down, or 'dependent'. This type may be called 'dependent oedema' by a healthcare professional. For most people, this oedema affects their legs and tends to improve overnight after you have had your legs up. See the separate leaflet called Oedema (Swelling).
If both legs are swollen to the same level, this is likely to be oedema. Causes of oedema affecting both legs symmetrically include:
- Heat. Some people will find their legs swell up a little in hot weather. Usually this is nothing to worry about and does not need treatment.
- Long journeys or being immobile for other reasons. If your legs are hanging down and not moving for long periods of time, you can develop swollen legs. This improves once you are walking about again, or once you lie down at night. This happens because your muscles are not working to move the blood in your blood vessels around. This means the blood pools in the bits of you which are hanging down, putting pressure on the blood vessels and forcing fluid out into the spaces between them. To avoid this, get up and walk around regularly if possible. If not, move your feet and legs around as much as you can.
- Pregnancy. Pregnant women may have swollen legs in late pregnancy. Usually this is nothing to worry about, but if you are pregnant, your midwife will be doing regular checks to be sure you don't have a blood pressure problem (pre-eclampsia) causing it.
- Heart failure. If you have this condition, your heart is not working as effectively to push the blood around your circulation. You may also feel out of breath, and this can be worse when lying down flat at night or on walking.
- Anaemia. This is a problem with the red blood cells of your body.
- Kidney diseases such as nephrotic syndrome, acute kidney injury and chronic kidney disease.
- Conditions where there are low levels of protein. If there are low levels of protein in the blood, less fluid is drawn into the blood from the surrounding areas. Conditions causing low protein levels include malnutrition, nephrotic syndrome, liver failure, and a gut condition called protein-losing enteropathy.
- Side-effects of medicines such as calcium-channel blockers.
- Having very low thyroid levels (hypothyroidism). This is normally accompanied by other symptoms such as tiredness and gaining weight.
- Idiopathic oedema. This means there is oedema but no specific cause has been found for it.
What causes one swollen leg?
There are numerous causes including:
- Injuries - for example, fractures, sprains, large bruises.
- Wear and tear arthritis (osteoarthritis) - in particular this might affect a knee (or both knees) or the big toe(s).
- Joint problems caused by inflammation - for example, gout, rheumatoid arthritis, psoriatic arthritis. One or more joints would be warm, red and painful.
- Skin infections - for example collections of pus (abscesses) or cellulitis.
- Skin reactions - for example an allergy to a bite or sting or medicine.
- Deep vein thrombosis (DVT). This is a blood clot in the deep blood vessels, which most commonly affects the calf. You are more at risk of a DVT if you have recently had a period of time when you didn't move very much. Examples include a long plane journey, an illness, an operation. If you have cancer, your risk is also increased.
- Bone infection (osteomyelitis).
- Lymphoedema. In this condition lymph fluid collects in the tissues because it can't drain very well. This is usually because the lymph nodes are blocked for some reason. This can happen after an operation, after radiotherapy, or due to cancer, injury or infection.
- Baker's cyst. This is a soft swelling at the back of your knee.
What are the symptoms of swollen legs?
Having 'swollen legs' is a symptom itself, but legs can be swollen in different ways. The clue to the cause (and therefore the treatment) may well be in the type of swelling. The swelling can be:
- One-sided or both-sided. Oedema due to conditions of general body systems is usually on both sides and is symmetrical (for example, if due to heart failure or pregnancy or kidney problems.) One-sided swelling is more likely to be due to a problem with a particular part of that leg.
- In a specific area or generalised. Swelling around joints is usually caused by injury or a type of arthritis. Swelling in specific areas of skin may be caused by allergy or infection. Swelling around the back of the heel suggests a problem of the Achilles tendon, etc. Generalised swelling, especially if on both sides, is likely to be oedema.
- Painful or painless. Painful conditions include infections, deep vein thrombosis (DVT), injuries and joint problems. Oedema is not usually painful, although legs can ache and feel tight.
- Accompanied by red (inflamed) or normal skin colour. If the skin is reddened, it may be due to an infection (such as cellulitis), or inflammation (for example, gout, rheumatoid arthritis or DVT). However if both legs are red then infection as a cause is very unlikely.
- Pitting or not. Pitting means that if you press a fingertip into the swollen area and then take your fingertip away, a dent remains in the skin. (See photo earlier in leaflet.) Oedema tends to be pitting. Lymphoedema, a condition where there is a blockage to lymph fluid, does not usually pit so much.
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Are there any other symptoms?
In addition to the leg or legs being swollen, there may be other associated symptoms. Again, these help give a clue to the cause of the leg swelling. For example:
- Breathlessness which started at the same time as the leg swelling might suggest heart failure (if both legs) or DVT (if one leg) spreading to the lungs (pulmonary embolism).
- A high temperature (fever) suggests infection.
- Tiredness might suggest a more general illness, such as anaemia or kidney problems.
- Diarrhoea might suggest a gut problem affecting the amount of protein being absorbed in the guts.
- Being yellow (jaundiced) suggests a liver problem, such as cirrhosis.
- Swelling in other places other than the legs - for example, in the tummy, hands or around the eyes. This would suggest a problem with another or a general body system rather than a problem with the leg or legs.
Do I need to see a doctor for swollen legs?
If you don't know why you have swollen legs, or you know the reason but it isn't settling then see your doctor. There are so very many causes for swollen legs that it is important to make sure it isn't due to something which needs treatment.
If your legs swell up a little in the hot weather but go down again overnight, you don't need to see a doctor. Or if both ankles are a little puffy after a long flight but there is no pain or redness of the calf, and the puffiness settles quickly then you do not need to see a doctor. Minor swellings from bites or trivial injuries don't usually need medical attention. In most other situations, it is wise to consult a health professional. If you have swollen legs and are pregnant, make sure you keep your regular appointment with your midwife. Your midwife will regularly check your blood pressure, and check your wee (urine) for protein to make sure your swollen ankles are not a sign of anything serious.
When should I see a doctor urgently?
In some situations, the cause of swollen legs can be serious, and you should see a doctor as an emergency. Obviously if you have had a serious injury and think you have a broken leg, you would attend an accident and emergency (A&E) department.
You should see your GP urgently if you:
- Think you might have a deep vein thrombosis (DVT). This might be the case if one calf is warm, swollen, red and tender. You might have swelling in the foot of that leg. A DVT is more likely if you are not very active - due to being in a wheelchair, for example, or after an operation or illness. It is also slightly more likely if you have recently been on a long flight or if you use a combined hormonal contraceptive in the form of a pill, patch or vaginal ring.
- Feel out of breath.
- Have a high temperature.
- Feel generally unwell in yourself.
- Are in severe pain.
- Notice your skin has turned a yellow colour.
What will the doctor do?
Your doctor will want more information about the swelling in your leg(s). For example, when it started, if it hurts and whether it comes and goes or stays much the same. They will also want to know if you have been on any recent long journeys or had any times when you were not very mobile recently, and if you are on any medicines.
The doctor will examine your legs and then may go on to examine other areas. This might include your chest and/or tummy and groin.
Will I have to have any tests?
This will depend on the information the doctor has obtained by listening to you and examining you. In some cases, no further tests will be needed. In others, tests will be advised. These might include:
- Testing your urine. This can usually be done in the doctor's surgery. The urine is tested with a dipstick to see if there is any protein in it, which might suggest a kidney problem, for example.
- Blood tests. You might have blood tests to check you for anaemia or heart failure . Tests may be done to check the function of your kidney, liver or thyroid gland.
- A chest X-ray. This would check you for conditions such as heart failure or a pulmonary embolism.
- An ultrasound scan of the leg. This can look at the nature of the swelling and establish where it is coming from. It can be helpful to diagnose tendon problems (such as Achilles tendinopathy), DVT and other problems in the veins of the legs.
- An X-ray if a fracture or infection of the bone is suspected.
Depending on the results of these tests, other investigations may be needed in some cases.
What is the treatment for swollen legs?
Treatment will be different depending on the cause. If the cause is fluid in the legs (oedema), this can often be relieved in the short term by taking tablets called 'water tablets' (diuretics). Diuretics increase the amount of fluid that the kidney filters off to be passed in your wee (urine). So when you take diuretics you eventually pee away some of the fluid which was collecting around your legs.
However, diuretics are not used for many causes of swollen legs. A few examples of some treatments of some common causes are as follows.
- DVT is treated with medicines to thin the blood and break up the blood clot.
- Heart failure is usually treated with a number of medications to improve your heart function, including diuretic medicines.
- Skin infections (cellulitis) or bone infections (osteomyelitis) are treated with antibiotics.
- Where the cause is a medicine, that medicine can usually be changed, or stopped, or the dose reduced.
Are there any complications?
Again this depends on the cause. The most common complication in swollen tissue is infection. Where the skin is stretched, it is more prone to be dry. If it is dry, it is more prone to breaks in the skin, allowing germs from the outside of the skin underneath. This can result in cellulitis of the legs. If this is the case a large area of the skin of the legs becomes hot and red. It may cause a high temperature (fever).
Further reading and references
Management of chronic heart failure; Scottish Intercollegiate Guidelines Network - SIGN (2016)
Cellulitis - acute; NICE CKS, January 2023 (UK access only)
Deep vein thrombosis; NICE CKS, February 2022 (UK access only)