Kind of looks like his femur is rotated, but could just be a bad case of splayed legs. (A rotated femur is usually a genetic defect, and typically can't be corrected without surgery and gets increasingly painful for the keet as it grows and gains weight, so I usually end up putting those keets down after 4 days with no improvement with a brace on the legs, ugh tho). Try bracing him up with a strip of vetwrap or stretchy self sticking bandage, or even a regular fabric bandaid cut in half lengthwise will work in a pinch. I have had pretty decent luck using a thin 1/4" strip of vetwrap tho (the length of the width of a normal sized roll), it only sticks to itself, good stuff. Here's a description of how I applied the vetwrap brace, and a pic...
I start with wrapping it around one leg one full wrap, then I do the same with the other leg making sure the legs are the normal distance apart (look at a normal keet for a comparison). Also make sure the ends of the wrap meet in the middle, then twist it between your fingertips and press it together pretty good to get it to adhere to itself. (Sometimes I'll put a thin strip of black electrical tape in the middle between the legs where I have twisted the ends together to help keep the ends from untwisting and coming loose, tends to keep the brace on longer). The vetwrap should be snug but not super tight around the legs. It loosens up over the next day or so and may come off on it's own, but the keet is usually walking fine by then anyway. Just keep an eye on the brace, replace it if needed. Usually within 2-3 days of having the brace on constantly, my keets have been fine.
It takes them a little while to get used to it, so you may need to pick him up and put him on his feet a few times until he can figure out how to deal with the brace. I don't think separating him from the others does much good, you want the others to stimulate it to get up and walk plus he will be stressed if separated... I'd just keep an eye on it and correct it/put it on it's feet if needed.
Bedding that provides good traction definitely is a MUST, if you can use old towels (make sure there are no loose strings, the keets will obsess about them and eat them), or if you can use rubberized shelf liner he may do better as far as getting traction and correcting/healing the leg problem.
This is not the best pic of the brace, but maybe you get the general idea...
ETA... The sooner you brace him up the more/better of a chance he has of healing. The more he uses the injured joint, the more damage is done.