The reason why a lot of people may be having leg problems in cornish x crosses is a simple solution. I didn't think about it until a few days ago but a lot of talk is said about how people want to raise the cornish past their intended 5 lb live weight intentions. Genetically they were bred to reach 5 lbs live weight at the max. Many people try to get 10 lb dressed weight birds out of these same strain of broilers. Their body frame wasn't genetically designed for this. Tips on avoiding this is to stick to a strain that is genetically designed for a "roaster" type chicken. Every strain is in someway a cornish x rock cross but there are different classes. Many belive the class is different only by the weight of the bird, that infact they are all the same genetic cross but at different ages. This however is not true. For instance a cornish hen, fryer, and roaster are all infact seperate strains of birds. Genetically designed for their intended weight and lifespan. So again to avoid leg problems don't raise your birds past the 6-8 week time frame for "fryer" lines. And if you choose to do so make sure you get a roaster line that is genetically equiped to handle a lifespan of 10-12 weeks and that their frame can hold 14 lbs of live weight. I know that a common strain is ross 308 for fryers. A common roaster strain however is a ross 508. Most hatcheries will tell you what strain of broiler eggs they are setting. If they don't I would find one that does. As this will help prevent deaths and injurys that normally happen with backyard enthusiast.