Sore calves often mark the day after a good run (or a long climb up steep stairs). But sometimes calf pain -- especially when not linked to any type of injury -- may mean something else is amiss, and it's something you definitely don't want to ignore.
Your leg has a network of arteries and veins that move blood to and from your muscle and heart. The veins you can see beneath your skin are called superficial veins, and they move blood farther into the muscle itself, toward deep veins. Little valves inside the veins prevent blood from flowing the wrong way. However, clots may form due to a rupture in the vein, damage to a valve or an injury to the leg. This is a deep vein thrombosis (DVT). The pain stems from the clot's presence causing a blood flow blockage, which results in swelling.
If a clot breaks loose -- an event called an embolism -- it could travel through your body, block an artery in the lung or brain, and damage your lung -- a pulmonary embolism -- or cause stroke. This doesn't usually happen, but when it does, it can be very serious and potentially deadly. Doctors usually prescribe anticoagulation drugs and keep tabs on the clot to make sure it's not growing. People with DVT who are overweight or who smoke should make lifestyle changes, as both of these factors increase the risk and severity of DVT.