Common Causes of Lower Limb Swelling and When to Seek Help

Lymphoedema is the medical term for persistent swelling, where the accumulation of excessive amounts of protein-rich fluid (lymph) results in swelling in one or more regions of the body. Whilst lymphoedema can be present in many body regions, depending on its cause, it most commonly affects the arms and legs.

1. Congenital abnormalities
Congenital abnormalities of the lymphatic system can lead to primary lymphoedema by affecting the development, number, or function of lymphatic structures. These structural differences may be present at birth (lymphoedema praecox) or become apparent later in life (lymphoedema tarda), resulting in reduced lymphatic drainage capacity and gradual fluid accumulation.

2. Cancer treatment
Having surgery, radiation therapy and/or chemotherapy for treatment of cancer, can impair lymphatic system function in ways that increase the risk of developing lower limb swelling. Surgical removal of lymph nodes—common in pelvic and gynaecological cancers—reduces the body’s ability to drain lymph, leading to fluid build-up in the legs. Radiation therapy can further damage lymph vessels by causing inflammation and subsequent tissue scarring (fibrosis), which can restrict fluid flow. Chemotherapy may also contribute indirectly through inflammation or increased infection risk. These combined effects can overwhelm the lymphatic system over time, resulting in swelling that may appear months or even years after treatment.

3. Recurrent skin infections (cellulitis)
Repeated episodes of skin infection (known as cellulitis) can damage lymphatic vessels through causing inflammation and tissue fibrosis. Each infection further impairs lymphatic drainage, creating a cycle where swelling increases the risk of future infections, and infections worsen the swelling.

4. Venous disease/insufficiency
Chronic venous insufficiency occurs when the veins in the legs cannot effectively return blood to the heart, leading to increased pressure in the lower limbs. Over time, this pressure can overwhelm the lymphatic system, contributing to fluid build-up and the development of lower limb lymphoedema.

5. Immobility/dependent oedema
Reduced movement, such as with prolonged sitting, standing and air travel, limits the muscle contractions that help pump lymph fluid back toward the abdomen. Without this muscle-pumping action, gravity causes fluid to pool in the lower limbs resulting in dependent oedema. If dependent oedema is not managed, it can develop into a secondary lymphoedema where swelling is persistent rather than intermittent.

6. Surgery or other physical trauma
Surgical procedures or traumatic injuries can directly damage superficial lymphatic vessels or lymph nodes, disrupting normal fluid transport. Scar tissue formation may also obstruct lymph flow. This can reduce lymphatic system function and cause a secondary lymphoedema to develop.

7. Chronic inflammation
Chronic inflammatory conditions, e.g. lipoedema, can lead to changes in tissue structure and lymphatic function by causing tissue fibrosis and vessel damage, reducing the efficiency of lymphatic drainage and contributing to fluid accumulation.

8. Obesity
Excess body weight places additional strain on the lymphatic system and can physically compress lymph vessels, impairing flow. Obesity is also associated with low-grade inflammation, which can further damage lymphatic structures and increase the risk of developing lymphoedema.

9. Malignancy
Cancers in the pelvic or abdominal regions can obstruct or invade lymphatic pathways, preventing normal drainage. Tumours may compress lymph vessels or nodes, while cancer-related inflammation can further compromise lymphatic function.

10. Filariasis
Whilst not common in Australia, Filariasis is a parasitic infection transmitted by mosquitoes that targets the lymphatic system. The parasites damage lymph vessels and nodes, leading to severe and chronic swelling of the lower limbs, commonly known as elephantiasis.