Though almost none of the Christian symbolism books write about it, the legs contain a lot of information for us. Very important symbolically in other systems, the leg is a passive symbol in Christianity; that is, we would not look at a leg and say, “Oh, this means . . .” but we could look at a leg to give us clues about what is going on.
Saint Rocco is usually depicted lifting his garment and showing the wounds on his legs, often with a dog licking the wounds. If we see bare feet with the marks of the crucifixion on them, we know that they belong either to the resurrected Christ or to one of the saints that were no known for experiencing the stigmata. If we see a man in shackles around his ankles we can assume it is somebody like St. Paul in prison.
Saint are almost always shown standing. It is a sign of power to stand. If a person is seated it most likely will be God on His throne or Mary Queen of Heaven or a else a great sinner on slovenly repose. If one is on their knees it is either a person in prayer such as the children at Lourdes praying before the Blessed Virgin, or someone under trial such as Jesus in the Garden or the prodigal son seeking forgiveness.
Bare legs are most often a sign of some sort of trial or sensuality. With few exceptions, most saints are pictured with their legs completely covered as if to say, “What I stand for is more important than my well turned leg!” Exceptions to this would be saints such as St. Sebastian in order to better show his suffering or Saint Michael in order to demonstrate his great power. Notice Satan, devils, and persons of loose morals are often showing off their legs. Rarer is the depiction of the Prince of Darkness in a long flowing robe, he is more of the miniskirt kind. Other times he has not human legs at all.
That is not to say that nudity/the body is something bad. When it is displayed for inappropriate reasons, then it is a sign of something gone wrong in the world. But when displayed modestly or for noble purposes, it is a thing of exquisite beauty.