If your ankle is swollen, and you haven't injured it, this may indicate that you are suffering from oedema. Oedema occurs when too much fluid is retained in the areas between the cells in our body.
According to Footsmart.com, there is a raft of factors that can cause ankle swelling, including taking oral contraceptives or undergoing hormone replacement therapy; abusing diuretics or laxatives; abusing drugs in general; eating too much salt and consuming too many carbohydrates; a history of phlebitis or varicose veins; sodium retention; allergic reactions, trauma to the ankle and neuromuscular disorders.
If you do have oedema, it will result in "pitting," which means that when you press down on the swollen area, an indentation will result and last long after you have quit pressing down.
Medicinenet.com notes that various medical conditions can result in ankle swelling. Arthritis is a rheumatic disease that can cause swelling and inflammation of the joints. Cellulitis, which is a bacterial infection of the skin and of the tissues underneath the skin, can spread and cause swelling, redness and tenderness. Pregnancy can cause swelling in the ankles. If you are pregnant and suddenly notice extreme swelling in your ankles, face or feet, contact your doctor. This could indicate that you are suffering from toxaemia or pre-eclampsia. One of the symptoms of congestive heart failure is swollen ankles because the body is filling up with fluid. If your kidneys are failing, your ankles may swell. If you have a blood clot in your leg, which is called deep vein thrombosis, this can result in swollen ankles.
Advancedvenoussolutions.com informs that a condition called venous insufficiency can cause swollen ankles. This condition is also called venous reflux and refers to the impaired return of venous blood from the feet and legs to the heart. This can result in varicose veins. Venous insufficiency occurs because a valve is absent or damaged or because the vessel walls are over-dilated and, as a result, blood pools rather than being returned to the heart.
Of course, any standard sprain, break or bruise to the ankle can cause it to swell. If you have been standing for too long, this may cause your ankles to swell. If you have a sunburn or have been bitten by an insect, expect to swell.
Medications that may cause your ankles to swell, according to Nlm.nih.gov, include blood pressure-lowering drugs, which are called calcium channel blockers (diltiazem, amlodipine, nifedipine, verapamil and felodipine); testosterone and hormone replacement drugs; antidepressants including MAO inhibitors (such as phenelzine and tranylcypromine); tricyclics (nortriptyline, desipramine and amitriptyline) and steroids.