Sam Laidlow needs surgery on a narrowed leg artery. The condition is rare, and endurance athletes are the people who get it

Sam Laidlow did not finish the Ironman World Championship in Kona on 10 October. The Frenchman, who won the world title in Nice in 2023, has confirmed that he has been struggling with iliac artery endofibrosis, a narrowing of a main artery to the leg, and will now have surgery, TRI247 reported.

It is an unusual diagnosis, but not an unknown one in triathlon. Austria’s Lisa Perterer had the same problem in both legs, had an operation at the end of last season, and finished sixth in Kona.

What the condition is

The iliac arteries carry blood from the abdomen into the legs. In endofibrosis, the inner lining of the artery, usually the external iliac, thickens with fibrous tissue and narrows the vessel. It is not the fatty build-up of atherosclerosis, and it typically affects young, fit people.

The proposed cause is mechanical: thousands of hours of hip flexion, especially in a low cycling position, combined with very high blood flow through the artery. TRI247 described it as a problem caused by repetitive hip flexion, which leads to the arterial wall thickening and reduced blood flow.

A 2025 scoping review in Vascular Specialist International gathered 43 studies published between 1997 and 2023, covering 443 athletes with the condition. Most were male endurance cyclists, and the left leg was affected more often than the right. The authors give an estimated global prevalence of 0.01%.

Why it is hard to spot

Because the narrowing matters most when blood flow is at its highest, symptoms usually appear only at hard efforts: pain, weakness, numbness or a sense of the leg “shutting down”. At rest the leg can seem healthy.

Perterer said it took her two and a half years to get a diagnosis. “Countless doctor visits, and the most common answer I got was: ‘You’re just getting older, Lisa’,” she wrote on Instagram, as reported by TRI247. “Running faster than tempo/IM pace? Not possible without my leg shutting down. On the bike, my balance was off (60/40), with constant pain.”

The review found that the ankle-brachial index, which compares blood pressure at the ankle with the arm, was used in about 84% of studies, alongside Doppler ultrasound and angiography.

What surgery involves

The review found that balloon angioplasty and stenting were more likely to be followed by a return of symptoms and further procedures. For athletes who want to keep competing, it concluded that endarterectomy with patch angioplasty, in which the thickened lining is removed and the artery is widened with a patch, remains the preferred treatment because of its high success rate and durability.

Recovery is slow. Perterer described four weeks without movement after her operation, followed by four weeks of light walking. She was diagnosed after winning Ironman Cozumel last November and had surgery straight after the T100 final in Qatar in December.

Laidlow has not said when he expects to race again. Much of the published evidence on endofibrosis comes from case reports and small series rather than trials, and athletes with leg pain at high intensity should see a vascular specialist rather than self-diagnose.