Leg pain can have many causes, but your description of aching after prolonged standing or sitting suggests a possible buildup of fluid in the leg veins (chronic venous disease, venous insufficiency). Chronic venous disease occurs when the valves in your leg veins don't work properly to keep blood moving efficiently from your legs to your heart.
Orthostatic hypotension — also called postural hypotension — is a form of low blood pressure that happens when standing after sitting or lying down. Orthostatic hypotension can cause dizziness or lightheadedness and possibly fainting. Orthostatic hypotension can be mild. Episodes might be brief ...
This type of low blood pressure happens after sitting up or standing too quickly. Poor blood flow. Conditions such as cardiomyopathy, heart attack, irregular heartbeat and transient ischemic attack could cause dizziness. Also, a drop in the total amount of blood flowing through the body may cause the brain or inner ear not to receive enough blood.