What are the possible causes of severe leg pain?

Pinched nerve: There can be many causes. A pinched nerve, a block in one of the blood vessels going to the leg, muscle overuse from too much work, etc. If the pain persists, there is swelling or discoloration please see your doctor.

Possible causes: Your pain could be as a result of many different things. A thorough history and physical exam and possibly some laboratory and radiology exams are needed to determine the exact cause. Causes of pain may include: trauma (fracture, sprain, arthritis), infection, metabolic conditions (gout), circulatory, musculoskeletal or biomechanical abnormality and neurologic conditions (neuropathy).