Why is there a hole at the bottom of the anti embolism stocking?

Anti embolism stockings are long stockings made of elastic material and are usually available in knee, thigh and leg lengths.

Anti embolism stockings provide graded compression - highest at the ankle and decreasing pressure upwards - mainly for bedridden patients to improve blood circulation in the legs and prevent venous thromboembolism.

They are white in color overall and are easy to observe for bleeding and other conditions in the leg. There is also an "observation hole" on the bottom of the foot area, so that medical staff can easily observe the patient's blood circulation.

The observation holes also provide ventilation and warmth when you don't need to observe feet.