Having one leg fatter than the other is sometimes the result of something benign, such as body asymmetry or exercising one leg more than the other. However, it is also sometimes a sign of something more serious, such as arthritis, water retention due to organ failure, or a blood clot.
One swollen leg is generally less cause for concern than swelling in both legs. If one leg is swollen, it is usually a sign that there is a problem within the leg itself. The swelling is perhaps due to arthritis or recent injury, or because the leg has been overused during workouts.
Swelling in one leg sometimes indicates a more serious condition such as a blood clot, which is able to travel through the body and cause harm elsewhere. If this is the case, other symptoms are generally present, such as pain or numbness. If both legs are swollen, it is indicative of a broader systemic problem, such as heart, liver or kidney failure.
If both legs are swollen, one leg sometimes swells more than the other so that it is difficult to notice the swelling in the leg that is less affected. Whether one or both legs swell up for no obvious reason, if the condition persists or if you experience other symptoms, such as chest pain or shortness of breath, consult a physician to ensure nothing serious is wrong, says WebMD.