All of the above Filas are steep in croup. This adds to the high rears that we see in this breed and our own.

In the first picture, we see a long legged Fila which raises his front. Had this Fila had the correct front, his rear would be very high.

High rears are not just a puppy phase in Mastiffs. High rears are a genetic result of poor planning when pairing dogs for breeding. Low tail sets usually indicate a steep croup and this leads to sloping toplines with loaded fronts.

When all the weight is pushed up front, through a sloping topline towards the front end of a Mastiff, it can create a number of issues. This places an extra burden on the dogs pasterns and leads to compression issues over time. It also creates poor aesthetics, as balance is compromised.

Level toplines with level rears are due to a number of factors, but the most important factor is a croup that is not too steep. A steep croup in a Mastiff can move the rear legs towards the front, instead of the rear legs being behind the dog as in the picture below............

(Beau Ideal)
The rear is level compared to the Filas above.
Unfortunately, some have come to accept high rears and expect that in our breed. If we recognize certain traits that can give us an indication of future issues, we can reduce these high rears and eventually make them a rarity instead of the norm.

When choosing a pup study it's parents and then study the pup. Become aware of traits like the angle of croup and try to pick level toplines. This will reduce your odds of winding up with a Fila rear instead of a proper Mastiff rear!

It should be worth noting, that as beautiful and acclaimed as Beau Ideal was, she actually was too long in the leg up front! This aided her nice topline, as it raised her front, but was structurally incorrect. This may have been accompanied by a short humerus as well.