I think the gabapentin may be contributing. It causes dependent
edema esp when it is hot and humid.

I have some problem with my left ankle...swelling and going down. It is a surgical site, with some internal damage to the instep so I think it is just edema from not draining well. + some arthritis.

I had very swollen legs and knees from Norvasc ...a blood pressure drug. Some of the calcium channel blockers do that too.

Sometimes it can be other things going on... if you have inflammatory issues, like arthritis, that will do it too. The swelling from fluid edema usually goes down when you put the leg up or at night when sleeping. And then it returns each day as the day wears on. Swelling from inflammation does not go down like that as a rule.