I've not seen a break, but the leg should be pretty swollen and bruised. Sprains are very common, from rooster horseplay to jumping down from roosts to high. He doesn't necessarily need quarantine, but I would cage him with food and water in the coop with the others for 1-2 weeks to rest the leg. Put a vitamin B Complex tablet crushed or dissolved in his food or water every day. Examine his footpad for bumblefoot (reddened swollen foot pad with a black dot,) look for swelling of the joints of the leg up to the hip, and feel for any displacement of the leg bones. My one experience with a hen who had a bad sprain lasted about a month or more with her limping and holding up the sore leg.He is 6-7 months. He eats a natural grain blend plus he is free range. He did not get vaccinated. And it's only 1 leg. Hope that helps. I'll be quarantining him now. How would I know if it's a break or a sprain. When I checked him I didn't notice any obvious breaks or swelling. Thank you!