THE ROACH BACK
A true roach is any convex (upward) curvature of the spine. It doesn’t really matter if it starts before the withers, after the withers, in the upper or lower back, or is higher or lower than the withers. If the spine is arched anywhere along its length, it’s roached, although the roach can certainly vary in severity. A dog straining at the leash can appear roached, but may not be. The rear is driving forward and the front is stationary; something has to give. However, if the dog displays a curvature when free standing, posed or not, and when moving freely at the trot, it’s roached.

The roach is most common in German stock. The idea seems to be that it results in a stronger back. Yes and no. An arched back, like a Roman stone archway, is better able to withstand the stress of downward pressure, whether of internal organs or a litter of young suspended from below, or the weight of tunneled earth from above (which is why rodents and shrews are roach backed). It is not efficient for movement at the trot. The spinal column is like a string of flattened pearls on a wire. If it is bent, pushing it at one end will increase its bend and it will not efficiently transmit power along its length. If it is straight, that power is very efficiently transmitted. Also, the bent spine does not effectively straighten when needed, but the straight spine can bend if and when necessary in galloping or jumping. In canines, the straight spine is ideal.

It is possible and desirable for the musculature of the loin to show an arch, without any curvature of the spinal column. This is because the muscles are anchored to the dorsal spines of the lumbar vertebrae which describe a gentle arch, much like the dorsal fin of a fish, while the vertebral disks of the backbone remain strung in a straight line. Racing greyhounds are often flat backed (their show cousins tend to be the roached ones) but still show a pronounced arch in the loin muscles. It makes them more effective gallopers, as the muscles cause the spine to act as a spring to gather energy and release it in a great leap. Some cats show slightly roached spines, but they are not long-distance trotters like most large canines. Cats are over endowed with muscling compared to dogs, and this muscling enables them to excel as leapers, pouncers and high speed chargers.

Good moving American show dogs have good, straight spines, but they are often too long and lack arch in the loin. These dogs can be very affective at a trot but often cannot perform well at the gallop or in jumping. German dogs that show a roach tend to be better at the gallop and jumping but are not as efficient trotters. Both excess length and curvature make the spine more vulnerable to injury, sap energy, and lack efficiency.