His feet are bent, he can't walk any distance without it hurting, and he's only 15, and wants to know if it's worth having an operation? I think he's just scared, personally. I don't blame him, a lot of people would be, especially at that age... but it sounds to me like he needs that operation. As for painful braces, well, it'll be more painful in 5 years' time when he can't walk at all (not to mention people skitting at him through school if it gets worse, which they will do, but that's a minor point); and as for growth stunting, well, I'd rather be short but walk properly than tall and crippled in 20 years. It might not need an operation, but he should definitely see someone.
Doesn't growth happen at the knees too, anyway? As well as the upper leg? They can't put the whole thing in a brace...