What causes varicose veins to form?

This question asks what goes wrong inside the vein. We read three publishers on it and set their passages side by side.

Weak valves let blood pool

The sources point to weak valves or weak vein walls, with blood collecting and the vein swelling over time. That is all this page claims.

Three publishers on the cause

The NHS describes the valve problem this way: "Varicose veins happen when the valves that control the flow of blood in your vein do not work properly."

Cleveland Clinic points at the vein itself: "Weakening of your vein walls causes varicose veins."

MedlinePlus adds the pooling step: "If the valves are weak or damaged, blood can back up and pool in your veins. This causes the veins to swell, which can lead to varicose veins."

A second MedlinePlus page says: "The vein swells from the blood that collects there, which causes varicose veins over time."

The source is those four passages. Our reading is a plain order of events: weak valves or walls, blood backs up, the vein swells.

What to put to your clinician

Ask the clinician treating you what is behind the weak valves in your own legs. The sources above do not answer that. Three guides are worth reading first: a patient guide to varicose veins, a radiology page on evaluation and treatment and a list of questions to ask your doctor.

Why your valves weakened is not answered here

None of the passages explains why a given person's valves weaken. A Westerville reader asking "why me" needs an exam, not a general source.