Heavy or tired legs, itching sensations, or swollen ankles can be the first signs of a chronic venous disease. The Clinical Etiological Anatomical Pathophysiological (CEAP) classification is the most used system to distinguish between different clinical manifestations, causes and locations of chronic venous disease.

You can find a comprehensive description on the manufacturer JOBST's website.
Venous Disease: Causes, Signs and Symptoms | JOBST USA
Signs and symptoms of chronic venous disease