What exactly causes "spurs"

[Jcavy]

My sister has her own gp and he something grew on his feet and she was worried it was "bumble foot" but I thought that strange since his environment was cleaned regularly and I found that it was spurs since there is no swelling.

But anyway, what causes and what can be done to prevent it.

[CavySpirit]

I don't think anything in particular causes them. I think that some pigs are just genetically prone to develop them.