Varicose veins commonly develop when changes in superficial vein walls and valves contribute to venous reflux. This allows blood to flow backwards and increases pressure within affected veins, which can gradually become enlarged and twisted.
Several factors may increase the likelihood of developing varicose veins, including family history, increasing age, pregnancy, excess body weight, previous blood clots and spending long periods sitting or standing.
This guide explains why varicose veins develop, how healthy leg veins normally work, what venous reflux means, which veins may be involved and the factors associated with a higher risk of varicose veins.
Quick Answer: Why Do Varicose Veins Develop?
Varicose veins commonly develop when changes in the walls and valves of superficial leg veins contribute to venous reflux. Venous reflux means blood flows backwards instead of continuing efficiently towards the heart.
This backward flow can increase pressure within affected veins. Over time, the veins may stretch, enlarge and become twisted or more visible beneath the skin.
Factors associated with a higher likelihood of varicose veins include:
- family history
- increasing age
- pregnancy
- previous deep vein thrombosis
- overweight or obesity
- prolonged standing
- prolonged sitting or reduced movement
- hormonal influences
These are risk factors rather than guarantees. Some people develop varicose veins without having every recognised risk factor, while others with several risk factors may not develop significant varicose veins.
Learn More About the Causes of Varicose Veins
How Do Healthy Leg Veins Work?
Veins are blood vessels that return blood towards the heart.
Blood returning from the legs has to travel upwards against gravity. The venous system uses several mechanisms to support this process, including one-way valves and the calf-muscle pump.
Many leg veins contain valves that open as blood travels towards the heart and close to help limit backward flow.
Movement also plays an important role. When the calf muscles contract during walking and other activity, they compress nearby veins and help propel blood upwards.
| Mechanism | Role |
|---|---|
| Vein valves | Help limit backward blood flow |
| Calf muscles | Help propel venous blood during movement |
| Vein walls | Contribute to normal vessel structure and function |
| Deep and superficial veins | Work together as part of venous return from the legs |
| Perforator veins | Connect the superficial and deep venous systems |
Changes affecting these structures can contribute to abnormal venous circulation.
How Venous Reflux Contributes to Varicose Veins
Venous reflux is backward blood flow within a vein.
When superficial vein walls or valves do not function normally, valves may no longer close effectively. Blood can then flow backwards and increase pressure within the affected venous system.
Over time, affected superficial veins may:
- enlarge
- stretch
- become twisted
- become increasingly prominent beneath the skin
This process does not necessarily begin in the same vein in every person.
Reflux can involve the great saphenous vein, small saphenous vein, tributary veins, perforator veins or connections between superficial and deeper veins.
For this reason, the visible location of a varicose vein does not always show where the underlying reflux originates.
What Are “Leaky Vein Valves”?
The phrase “leaky vein valves” is an informal way of describing vein valves that do not close effectively.
Healthy valves help restrict backward blood flow. When valve function is impaired, blood may reflux in the opposite direction and contribute to increased venous pressure.
However, varicose vein disease should not be thought of simply as one faulty valve at the groin or behind the knee.
Changes in the vein wall, valve function and the pattern of reflux can involve different parts of the superficial venous system.
Great Saphenous Vein Reflux
The great saphenous vein (GSV) is a major superficial vein running from the foot along the inner leg and thigh before joining the deeper venous system near the groin.
Its valves normally help maintain blood flow in the appropriate direction.
When reflux occurs within the great saphenous system, pressure may increase in connected superficial branches. This can contribute to varicose veins along areas such as the inner thigh, around the knee or lower in the leg.
This does not mean that every visible varicose vein along the inner leg is caused by great saphenous vein reflux. The underlying pattern varies between individuals.
Small Saphenous Vein Reflux
The small saphenous vein (SSV) is another important superficial vein.
It travels mainly along the back of the calf and commonly joins the deeper venous system around the back of the knee, although its anatomy can vary between people.
Reflux involving the small saphenous system may contribute to varicose veins around the calf or back of the leg.
The small saphenous vein should not be confused with the popliteal vein. The small saphenous vein belongs to the superficial venous system, while the popliteal vein is a deep vein located behind the knee.
Perforator Vein Reflux
Perforator veins connect the superficial venous system with the deep venous system.
Their valves normally help direct blood between these systems.
When some perforator veins become incompetent, abnormal blood flow may contribute to increased pressure within connected superficial veins.
Not every person with varicose veins has clinically significant perforator reflux, so the importance of individual veins needs to be considered in the context of the overall clinical findings.
What Increases the Risk of Varicose Veins?
Varicose veins usually cannot be attributed to one single factor.
Genetics, ageing, pregnancy, previous venous disease and other factors can influence the likelihood of developing them.
Family History and Genetics
Varicose veins can run in families.
People with close relatives who have varicose veins may have a higher likelihood of developing them.
Inherited differences may influence characteristics such as vein-wall structure or valve function.
However, genetics does not guarantee that a person will develop varicose veins, and people without an obvious family history can also develop them.
Increasing Age
Varicose veins become more common with increasing age.
Age-related changes can affect the elasticity of vein walls and the function of vein valves, potentially making efficient venous return more difficult.
Age is therefore a recognised risk factor rather than a direct guarantee that varicose veins will develop.
Pregnancy
Varicose veins may first appear or become more noticeable during pregnancy.
Several changes can contribute, including:
- increased blood volume
- hormonal changes
- changes in venous blood flow
- increasing pressure within the abdomen as pregnancy progresses
Some pregnancy-related varicose veins may improve after childbirth, while others may persist.
Assessment and treatment decisions during pregnancy require individual medical advice.
Previous Deep Vein Thrombosis
A previous deep vein thrombosis (DVT) can affect blood flow within the deep venous system.
A blood clot may damage valves in affected deep veins, and some people develop longer-term venous changes after DVT. These are sometimes referred to as post-thrombotic changes or post-thrombotic syndrome.
A previous DVT is therefore important medical history when assessing leg swelling, skin changes or varicose veins.
Learn About Deep Vein Thrombosis
Overweight and Obesity
Overweight and obesity are associated with a higher likelihood of varicose veins.
Additional body weight may influence venous pressure and can contribute to the overall burden on the venous system.
However, body weight is only one factor. People across a wide range of body sizes can develop varicose veins.
Prolonged Standing
Occupations or daily routines that involve long periods of standing may be associated with a higher likelihood of varicose veins.
When someone stands relatively still, the calf-muscle pump is less active than during walking.
Regular movement can help activate the calf muscles when prolonged standing cannot be avoided.
Prolonged Sitting and Reduced Movement
Long periods of sitting can also reduce activation of the calf-muscle pump.
Changing position and incorporating regular movement into the day may support normal venous circulation where practical.
This should not be interpreted as a guarantee that regular movement will prevent varicose veins, particularly when genetic, age-related or other risk factors are present.
Hormonal Influences
Hormonal changes may affect vein walls and venous function.
This may partly contribute to changes seen during pregnancy and other periods of hormonal change.
Hormonal influences are best considered as one component of a person’s overall risk rather than as a single cause.
Does Smoking Cause Varicose Veins?
Smoking should not be described as the single direct cause of varicose veins.
Varicose veins are generally associated with a combination of changes affecting superficial vein walls, valve function, venous pressure and individual risk factors.
Smoking has well-established harmful effects on cardiovascular and general health. People who smoke can discuss smoking cessation with an appropriate healthcare professional.
Are Varicose Veins Genetic?
Genetics can contribute to varicose vein risk, but varicose veins are not determined by genetics alone.
Having a parent or close relative with varicose veins may increase susceptibility. Age, pregnancy, previous venous disease, body weight and prolonged periods of limited movement may also contribute.
This means members of the same family can develop very different patterns and severity of venous disease.
Can Varicose Veins Be Prevented?
There is no proven way to prevent every case of varicose veins.
Some important risk factors, including genetics, increasing age and pregnancy, cannot simply be avoided.
General measures that may support circulation or help manage some leg symptoms include:
- walking and remaining physically active
- avoiding unnecessarily long periods without movement
- changing position during prolonged sitting or standing
- maintaining a healthy weight where appropriate
- elevating the legs when this helps relieve swelling or discomfort
These measures should not be described as a cure or a guarantee that varicose veins will not develop.
What Symptoms Can Occur With Varicose Veins?
Some people have clearly visible varicose veins with few symptoms, while others experience discomfort.
Possible symptoms include:
- aching
- throbbing
- leg heaviness
- tired or uncomfortable legs
- ankle or lower-leg swelling
- itching
- cramping
- discomfort following prolonged standing
- changes in skin colour or texture
These symptoms can have causes other than varicose veins. The presence of visible veins does not automatically prove that they are responsible for a person’s pain, swelling or other symptoms.
Explore Varicose Vein Symptoms
Can Varicose Veins Cause Complications?
Many people with varicose veins do not develop serious complications.
However, chronic venous disease can sometimes be associated with:
- persistent swelling
- skin pigmentation
- venous eczema
- inflammation of superficial veins
- bleeding from a varicose vein
- changes in the skin and underlying tissues
- venous leg ulcers
New, persistent or worsening symptoms should be appropriately assessed rather than assumed to be an unavoidable consequence of having varicose veins.
How Is the Cause of Varicose Veins Assessed?
Assessment usually begins with a medical history and clinical examination.
A clinician may ask about:
- current symptoms
- when symptoms occur
- family history
- previous pregnancies
- previous DVT or other blood clots
- previous vein treatment
- medications
- occupation and activity
- other relevant medical conditions
The legs may also be examined for visible veins, swelling, skin changes and other signs that may be associated with venous disease.
Duplex Vascular Ultrasound
When clinically indicated, duplex vascular ultrasound can provide information about vein anatomy and blood flow.
Ultrasound may help determine:
- whether venous reflux is present
- which superficial veins are affected
- the direction of blood flow
- the location and extent of reflux
- relevant connections between superficial and deep veins
- anatomical findings that may influence treatment planning
Not everyone with visible spider or reticular veins automatically requires vascular ultrasound. Whether imaging is appropriate depends on symptoms, examination findings and the suspected underlying condition.
Learn About Vascular Ultrasound
Does the Cause of Varicose Veins Affect Treatment?
Yes. The veins involved and the pattern of venous reflux can influence which treatment options may be considered.
Two people can have varicose veins that look similar from the outside but have different underlying venous anatomy.
Treatment planning may therefore consider:
- symptoms
- clinical examination
- ultrasound findings where indicated
- which veins are affected
- the location and extent of reflux
- previous treatment
- relevant medical history
- individual circumstances and preferences
Treatment should not be selected solely according to the appearance of a visible vein.
Varicose Vein Treatment in Melbourne
Not every person with varicose veins requires treatment.
Where treatment is clinically appropriate, the options considered depend on the underlying venous problem, symptoms, anatomy and assessment findings.
Depending on individual circumstances, treatment pathways may include conservative management or procedures directed at selected abnormal superficial veins.
Sclerotherapy
Sclerotherapy involves injecting a sclerosant into a selected vein to cause it to close.
It may be considered for certain superficial veins depending on their size, anatomy and underlying circulation.
Ultrasound-Guided Sclerotherapy
Ultrasound-guided sclerotherapy (UGS) uses ultrasound to help identify and guide treatment of selected veins.
Suitability depends on the anatomy involved and individual clinical findings.
Endovenous Laser Treatment
Endovenous laser treatment (EVLT) uses thermal energy delivered within a selected superficial vein to close it.
EVLT may be considered for selected veins with venous reflux where clinically appropriate following assessment and ultrasound.
Cyanoacrylate Vein Closure
Cyanoacrylate vein closure, sometimes called vein glue, uses a medical adhesive to close selected superficial veins with reflux.
Whether it is suitable depends on factors including vein anatomy, ultrasound findings, medical history and individual circumstances.
Ambulatory Phlebectomy
Ambulatory phlebectomy involves removing selected superficial varicose vein branches through small openings in the skin.
It may be considered alone or in combination with another treatment where clinically appropriate.
For a broader comparison of treatment pathways:
Compare varicose vein treatment options in Melbourne
When Should Varicose Veins Be Assessed?
Consider seeking medical advice if varicose veins are associated with persistent or concerning symptoms such as:
- ongoing pain or heaviness
- persistent leg or ankle swelling
- significant changes in skin colour
- eczema-like changes around the lower leg
- bleeding from a varicose vein
- a painful, hard or inflamed superficial vein
- a wound around the lower leg or ankle that heals slowly or repeatedly returns
New unexplained pain or swelling affecting one leg can have causes other than varicose veins, including deep vein thrombosis, and may require prompt medical assessment.
Frequently Asked Questions
What is the main cause of varicose veins?
Varicose veins commonly develop when changes in superficial vein walls and valves contribute to venous reflux, allowing blood to flow backwards and increasing pressure within affected veins.
Genetics, age, pregnancy and other factors may influence a person’s susceptibility.
What are leaky vein valves?
“Leaky vein valves” is an informal description of valves that do not close effectively.
When this happens, blood may flow backwards. This abnormal backward flow is known as venous reflux.
Does having varicose veins mean the valve at my groin has failed?
No. Reflux can occur in different parts of the superficial venous system, including the great saphenous vein, small saphenous vein, tributaries, perforator veins and their connections.
When clinically appropriate, vascular ultrasound can help identify the pattern and location of reflux.
Can varicose veins occur behind the knee?
Yes. Varicose veins can occur around the back of the knee and calf.
In some people, reflux involving the small saphenous vein or connected superficial veins may contribute.
Are varicose veins inherited from your mother or father?
Varicose veins can run in families, but inheritance is not as simple as receiving the condition from one particular parent.
Family history is one recognised risk factor among several.
Can a DVT cause vein problems later?
Yes, in some people. A previous DVT can damage deep vein valves and alter venous circulation.
This may contribute to longer-term venous problems known as post-thrombotic changes or post-thrombotic syndrome.
Can pregnancy cause permanent varicose veins?
Varicose veins can develop or become more prominent during pregnancy.
Some improve after childbirth, while others may persist. The outcome varies between individuals.
Does sitting all day cause varicose veins?
Prolonged sitting may contribute to risk because the calf-muscle pump is less active when the legs remain relatively still.
However, sitting should not be considered the sole cause of varicose veins.
Does standing all day cause varicose veins?
Long periods of standing are associated with a greater likelihood of varicose veins.
Other factors, including genetics, age, pregnancy and venous anatomy, may also contribute.
Will losing weight make varicose veins disappear?
Not necessarily. Weight management may support general health and may reduce factors contributing to venous pressure where excess weight is present, but losing weight does not guarantee that existing varicose veins will disappear.
Can exercise repair damaged vein valves?
Exercise supports circulation and activates the calf-muscle pump, but it should not be described as repairing an incompetent vein valve.
Persistent symptomatic venous reflux may require clinical assessment.
Can varicose veins return after treatment?
Yes. Varicose veins can recur, and new abnormal veins may develop after treatment.
Treatment does not guarantee that a person will never develop varicose veins again.
Find the Right Vein Assessment Pathway
The reason varicose veins develop can differ between individuals. Visible veins alone may not show where reflux originates or which veins are involved.
Clinical assessment and, where appropriate, vascular ultrasound can help clarify the underlying pattern before treatment is considered.
Compare varicose vein treatment options in Melbourne
Medical Disclaimer
This article provides general educational information only and is not a substitute for individual medical advice, diagnosis or treatment.
The causes of leg symptoms can vary, and visible varicose veins are not always responsible for pain, swelling or other symptoms. An appropriately qualified healthcare professional can advise whether further assessment or treatment may be appropriate for your circumstances.
Seek prompt medical attention for new unexplained one-sided leg pain or swelling, particularly if deep vein thrombosis is a concern. Call Triple Zero (000) for urgent symptoms such as sudden difficulty breathing, chest pain, coughing up blood or fainting.
