Abnormal sensations in the leg can be due to pinching of the nerve root as it comes out of the vertebral column, compression or degeneration of nerve(s), reduced blood supply due to blockage of an artery, or blockage of impure blood flow from leg towards the heart through leg veins. It is important to know exact location and extent of the current like sensation (inner / outer / front / back / upper / lower portion of the leg), and also associated symptoms (like swelling, redness, increased temperature, weakness) to be able to decide what is its probable origin. Also, a clinical examination by a neurologist can find out additional information about its cause. In your case it appears to be stretch upon the nerve root, the most common cause of such a symptom. You should first consult a neurologist. Investigations like MRI of the lower spine can show if the nerve roots are compressed / pinched. A Nerve Conduction Study can also be helpful. A sonography study / doppler study can identify blockages in the blood vessels. All these tests are relatively expensive; a doctor’s advice will be the right first step.