Drake having trouble with his legs

[Worm94]

Hello! A couple years ago we rescued two jumbo pekins off of the river, a duck and a drake. The drake had a leg injury when we caught him and his ankle was swollen but his hips were alright. Neither had good health, obviously, so we spent a while just giving them all the peas they could eat along with the all-flock the chickens got and some duck-specific feed as well. There were no other signs of illness or anything weird at that time nor since.
The duck is fine now, but the drake's never quite recovered on that one leg and it's taken a significant dip lately and I'm wondering if there's anything I can do for him. He's in good spirits and as active as he can be, but the one leg is worse and I guess because the other leg has been compensating for a while, it's not doing so well either.
Neither leg is paralyzed I don't think, but they don't seem to support his weight anymore.
Took a short video this morning, so I'll try and attach that here.
They still get peas here and there as a treat, and it's been very cold so rarely a handful of corn gets tossed out and whoever's fast enough gets a couple pieces, as well as veggie scraps whenever I've got em. I don't know how to upload a video so I posted a private video via youtube, I hope that works.

 

[nuthatched]

Does he get niacin supplements?

 

[Worm94]

Does he get niacin supplements?

We were giving him higher niacin based foods but we can try some supplements now. Would human vitamin B pills do anything (I only ask because we have a lot of those on hand) or should we just go straight to buying duck specific supplements?

 

[nuthatched]

We were giving him higher niacin based foods but we can try some supplements now. Would human vitamin B pills do anything (I only ask because we have a lot of those on hand) or should we just go straight to buying duck specific supplements?

Are they normal b complex?
https://www.backyardchickens.com/threads/help-weak-duckling….1640727/#post-28025822

 

[Worm94]

Let me check

Thank you, I went and looked at our pill bottles and a couple say B3 and I think that's niacin from a quick search around?
I just worry, I don't want to get it wrong somehow. I figure he'll definitely eat the pills if offered, they take treats from me all the time.
It might be that what we're feeding them isn't enough niacin because of their size, and if that's the case I'll definitely up what they get but all the others seem alright so far.
It might be too, that his old injury is flaring because of the cold and I've wondered about arthritis. If that was the case, I remember I was able to give small doses of some pain meds to a chicken a couple times, but ducks are new territory.
I'm reading thru some forum stuff trying to get a better idea too.