Iliac artery endofibrosis (IAE) is a rare but significant condition affecting endurance cyclists and runners. This vascular disorder — associated with repetitive strain and high-intensity exercise — can compromise blood flow to the legs, causing pain and reduced performance. Understanding the causes, symptoms, and treatment is essential for athletes wanting to maintain performance and avoid long-term complications.
What is iliac artery endofibrosis?
Iliac artery endofibrosis is a condition in which the inner lining of the external iliac artery thickens abnormally. This thickening reduces the artery’s diameter and elasticity, limiting blood flow to the legs during exercise.
Which arteries are involved?
Most cases involve thickening of the external iliac artery. Sometimes, though, the thickening affects other vessels, such as the common iliac or femoral arteries. Often, only one side is affected.
Causes of iliac artery endofibrosis
The exact cause isn’t fully understood, but several factors contribute:
- Repeated mechanical stress. Repetitive strain leads to fibrous tissue forming and narrowing inside the artery. Because of prolonged high-intensity exercise, elite athletes are particularly at risk.
- Cycling posture. The forward, hip-flexed position of a cyclist can cause the artery to kink.
- Bike fit. An improper bike fit increases strain and kinking of the artery.
- Enlarged hip flexor. An enlarged iliopsoas (hip flexor) muscle can kink the iliac artery.
Symptoms of iliac artery endofibrosis
Symptoms occur with exercise and stop almost immediately with rest. The most common is muscle cramping in the buttocks, thighs, or calves. Other symptoms include numbness, tingling, coldness, fatigue, and reduced power output in the legs.
How is iliac artery endofibrosis diagnosed?
This condition is often underdiagnosed, because its symptoms overlap with other causes of exertional leg pain, such as:
- Metabolic or muscular conditions, such as anaemia or muscle diseases (McArdle’s syndrome)
- Nerve entrapment in the groin, thigh, or calf, or sciatica
Diagnosis needs a thorough assessment. Your doctor examines you before and after exercise to assess the leg muscles, blood supply, and nervous system. Sometimes a whooshing sound (a bruit) can be heard over the pulses in the groin.
Specific tests confirm the diagnosis:
- Ankle-brachial index (ABI). Blood pressure is measured in the arms and ankles before and after five minutes of intense cycling or running, and the ankle pressure is divided by the arm pressure. A normal ratio is around 1.0; a lower value indicates reduced blood flow to the legs. Athletes often have normal ABI values at rest, but the ABI in the affected leg typically drops after exercise — a level below 0.5 is highly suggestive of this condition.
- Doppler ultrasound of the arteries uses sound waves to measure blood-flow speed, which is much higher after exercise. Ultrasound can also reveal thickening or kinking of the arteries.
- MR angiography (MRA) gives a more detailed view of the artery, including its thickness and any kinking. This is often needed to decide whether surgery is required.
- Blood tests help rule out metabolic causes of vascular disease, such as diabetes, high cholesterol, and anaemia.
Treatment of iliac artery endofibrosis
Treatment depends on the severity of symptoms and imaging findings.
Conservative treatment
For milder symptoms, we recommend conservative management: reducing training intensity and duration, adjusting the bike setup to minimise hip flexion, and physiotherapy to improve hip flexibility and strength (with a focus on the psoas muscle). Antiplatelet medication, such as aspirin, may improve blood flow. Changing sporting activity is another option.
Ways to optimise the bike setup include raising the handlebars, bringing the saddle forward to avoid hip hyperflexion, and avoiding pulling upwards on the pedals (which can enlarge the psoas muscle).
Surgery
Open surgery is recommended for more severe symptoms and pathology. Less invasive options, such as stents, aren’t appropriate for this condition.
The type of surgery depends on the pathology:
- If the external iliac artery is kinked by its attachment to the psoas muscle, surgery releases the fibrous tissue.
- If the external iliac artery is longer than average, it may be surgically shortened.
- If the symptoms are caused by fibrosis of the vessel wall, an endarterectomy removes the fibrosis, thereby restoring blood flow.
Outcomes of surgery are usually excellent, with a return to high performance within about three months.
Frequently asked questions about iliac artery endofibrosis
How common is iliac artery endofibrosis in elite athletes?
It’s more common than many realise. One study suggested that up to 20% of elite cyclists may have some degree of iliac artery flow limitation. Skiers, runners, and rowers can also be affected.
How do you tell iliac artery endofibrosis from compartment syndrome?
Both cause exertional leg pain, but the pattern differs. Iliac artery endofibrosis typically causes cramping in the buttock, thigh, or calf that eases almost as soon as you stop, often with a drop in the post-exercise ABI. Chronic exertional compartment syndrome causes a deep tightness that takes longer to settle and is not associated with vascular changes. Exercise testing and imaging distinguish them.
Can you keep cycling with iliac artery endofibrosis?
With milder disease, yes — by reducing training load, optimising your bike fit to reduce hip flexion, and working on hip flexibility. More severe cases limit performance and may need surgery, so persistent exertional leg pain shouldn’t be ignored.
Does bike fit cause iliac artery endofibrosis?
Bike fit isn’t the sole cause, but the hip-flexed cycling posture contributes to arterial kinking, and a poor fit adds to the strain. Optimising the fit — raising the handlebars and bringing the saddle forward — is a key part of conservative treatment.
Does iliac artery endofibrosis need surgery?
Not always. Milder cases are managed conservatively. Surgery is reserved for more severe symptoms and pathology, and outcomes are usually excellent, with most athletes returning to high performance within about three months.
Final word from Sport Doctor London about iliac artery endofibrosis
Iliac artery endofibrosis is a unique challenge for endurance athletes, particularly cyclists and runners. Early recognition of symptoms, an accurate diagnosis, and appropriate treatment can prevent long-term complications and help athletes continue performing at their best.
If you have exertional leg pain that isn’t settling, Dr Masci can assess you in London and, where a vascular cause, such as iliac artery endofibrosis, is suspected, arrange appropriate exercise testing and onward vascular referral. Contact the team here or call +44 (0) 203 488 0350.
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