duckling with limp leg

Yesterday, the duckling was running all around. This morning, it has a limp leg. How do I go about checking if it has a broken leg without possibly hurting it further? If it is broken, what do I do for it? Can I do anything for it? It is healthy otherwise and I would hate this to be its undoing.

Other than the possibility of a broken leg, what else might it be? Could it be a deficiency thing? If so, why only one leg and so quickly? The other leg is fine. Both legs are a nice color of orange, no outward sign of injury and no bruising that I could see.

I am finding that it is a never ending struggle with these little guys. I wish things were easier... This duckling is about a month old.

I have had this happen and with the young one I just watched. It rested more often and by the next day there was no sign of a sore leg at all so I think they just over exerted running through the uneven horse paddock.
I have had a couple older ducks with sore legs. If they seem to get worse not better get some help to catch it easier so that you don't have it hurt itself more. Then check for anything that would cause pain like a sore or infection (sorry can't help with that). Anyway, I've had 2 sore legged hens one Rouen which I popped into a large dog kennel with water and food within reach but so that she couldn't move much. It took about 2weeks but she's perfectly fine now however I thought we were going to put her down because it seemed bad. Now I was away and when I came home found a Buff hen with a sore leg so she is currently on bed rest and yesterdays check showed me that she can weight bare now so a few more days to fully heal Hope your ducky did nothing more then overexert

The duckling is getting along fine. It still has a limp leg, but has learned (quite quickly I might add) to hopping around fairly quickly on the one good leg. It is eating and drinking and still seems to show no sign of pain. We have decided to continue to watch it, but leave it alone as it seems to have learned to get around its problem.