My husband was having an issue with swollen ankles and feet. Besides the usual things that help (drinking a lot of water, some exercise, lower salt, keeping legs elevated) what helped was an increase in his prescription diuretic med, which he already took for high blood pressure.

In the past, I also briefly had swollen lower legs and feet. The last time it was from prolonged sitting on planes and in the airports. It resolved itself, quickly. Other times were in reaction to injuries, such as to my knees or other leg areas after bad falls. My nephrologist also always checks them since it can be a sign of worsening kidney issues.

Have you tried the other "usual things"? The leg elevation is an easy and pleasant enough one.