There are many causes for leg pain including Achilles tendinitis, varicose veins, deep vain thrombosis They're more likely to happen if you're inactive for long periods, like on a long flight or car ride. You're also at risk if you're overweight, or you smoke, or take certain medications....This can happen when the arteries in your legs become damaged and hardened....some other causes are herniated discs,sciatica, stenosis of spinal canal etc...I would suggest you to consult nearest physician for clinical examination if needed they will only refer you to concerned specialists.