While
the exact mode of inheritance is unknown, it is probably polygenetic.
The congenital form of medial luxation (kneecap dislocated to the inside of the knee) is most common in toy breeds, not excluding Havanese, and is considered inherited although
the exact mode of inheritance is not known.
The exact mode of inheritance of LPD has been debated among researchers.
Regardless of
the exact mode of inheritance, statistical analysis of this and other studies reveals that LPD has a high degree of heritability.
The condition is rare but is seen more commonly in Staffordshire bull terriers in which pedigree analysis supports a hereditary etiology for the condition but is insufficient to determine
the exact mode of inheritance, [148, 149].