The leg that swells with congestive heart failure is actually both legs.
If you have only one leg that is swelling, then it's a sign of a blood clot or a vein issue, instead of heart failure, although swelling in one leg could also be a sign of poor circulation.
When you have congestive heart failure, the congestive heart failure often causes swelling to occur in both legs, and it often starts in your feet and ankles.
The fluid buildup with congestive heart failure that leads to swollen legs, feet and angles is called peripheral edema and is caused by gravity as well as your heart's ability to pump blood effectively.
When your heart is struggling to pump blood, like it does in congestive heart failure, your kidneys retain excess salt and excess water.
And the blood flow also slows down.
When this occurs, it results in blood backing up in your veins, forcing fluid into your body's tissues.
And because this is a systemic circulatory issue, which is often linked to right sided heart failure, the gravity causes the fluid to settle downward, affecting both your legs equally.
If the swelling in your legs is related to congestive heart failure or heart failure, you will usually notice that when you press a finger into the swollen area of the leg, that it leaves an indention that takes awhile to fill back in, which is called pitting edema.
You should contact your doctor if the swelling is occurring in one leg only as it's often a sign of a blood clot or vein issue, instead of heart
Or if the swelling in your leg or legs is accompanied by any sudden weight gain, fatigue or shortness of breath.
Or if the swelling in the leg or legs is accompanied by any pain, redness or warmth.
If you think you may be experiencing congestive heart failure you should seek medical attention as that is also a serious health issue that needs to be checked by a doctor.