Fluid buildup or inflammation may cause pain and swelling in the left leg, explains Mayo Clinic. Fluid buildup in the leg is called peripheral edema and it has various potential causes, including conditions of the lymphatic and circulatory systems. Inflammation may result from rheumatoid arthritis, among other causes.
Standing or sitting too long may cause fluid buildup that leads to swelling of the leg, according to Mayo Clinic. The condition may also result from serious health issues including heart failure, thrombophlebitis, pericarditis, lymphedema and cirrhosis. It may also occur from chronic kidney disease, acute kidney failure or a reaction to prescription medications. A leg may swell as a result of inflammation due to injury such as a broken or sprained ankle. Serious conditions that may cause inflammation include cellulitis, knee bursitis, Achilles tendon rupture, gout and osteoarthritis.
If leg swelling occurs in tandem with prolonged chest pain, confusion, fainting, dizziness or difficulty breathing, seek emergency medical care, advises Mayo Clinic. Such combined symptoms may indicate a serious heart condition or a blood clot in the lungs. Also seek immediate medical care if the leg begins to swell for no known reason or as the result of a physical injury. Over-the-counter pain medication may reduce painful swelling in the leg, and elevating the leg may decrease the swelling associated with fluid buildup. Patients should not stop taking prescription medications without consulting a doctor, even if the medication is suspected of causing the swelling.