Innate malformations of the skeleton appear relatively frequent, particularly in the limbs. The occurring defects are extremely variable, and appear isolated or combined with other changes.
For a perfect development and growth of the skeleton  a large amount in genes is required, so that the genetic causes for malformations are varied and their appearance cannot be explained yet completely by their molecular interference.
On this account the  limb malformation are classified by clinical aspects, which often overlap with molecular defects.