The Short Loin and Other Myths

How often have you heard it?  "The Lhasa should have a long body and a short loin".  "A long loin is not good as it is weak."  "A short loin is strong".  And the good word associated with "back" is "short".  The bad word is "long".  Where did all of this come from?  Certainly not from the standard which in all cases throughout the world asks for a rectangular outline - "longer than tall".  And no Apso standard in the world asks for a short loin.  No standard even defines where the loin is.  So in this article we will attempt to answer 4 questions:

1. Where exactly is the loin, and how does one measure it?

2. What determines loin length?

3. If it should be "short", why?

4. If it should be long, why?

I would like to lay a bit of anatomical foundation for the discussion.  The axial skeleton of the dog consists of a skull, 7 cervical (neck) vertebrae, 13 thoracic vertebrae, each one carrying an attached rib, 7 loin vertebrae, the sacrum and the tail with a variable number of vertebrae - up to 26.

The flexibility of the torso is mainly confined to the loin.  Why? The torso consists of the thoracic vertebrae and their attached ribs, and the loin and sacrum.  There is no mobility in the sacrum which consists of 3 fused vertebrae.  Likewise the chest cavity is a more or less rigid box containing the heart and lungs.

The first 9 ribs are attached fairly rigidly to the sternum.  There can be very little flexion or extension at all in this segment. The next three ribs are connected at their terminal ends to a rubbery piece of cartilage which then connects to the sternum.  Very little freedom of movement there either.  The last, 13th, rib is floating and not connected except by muscles to the 12th rib.  In addition to the bony and cartilaginous  attachment of the ribs, they are also connected to each other by strong bands of muscle which can contract to narrow the chest cavity laterally, or relax to expand it.  These muscles also limit the flexion and extension of the spine.

What we are left with, to the rear of the rigid protective box of ribs and thoracic spine, is the loin - 7 vertebrae which are free to move in dorsal flexion and extension, lateral flexion, and twisting motions as well.

Well, what is the loin and what is it that some people erroneously call the loin? The loin is the chunk of lumbar spine and paraspinal muscles as indicated in the attached diagram.  The loin is 7 vertebrae long.  The entire spine from the top of the scapular spine (at the 2nd thoracic spinal process) to the sacrum is 19 vertebrae long.  The lumbar vertebrae are larger than the thoracics, so that the loin comprises approximately 45% 0f the length of the back from wither to pelvis. The only anatomically correct way to measure the loin is along the spine, not on the sides of the dog.

Some have stated that the loin is the area from the last rib to the wings of the pelvis.  Again, this is not the loin.  the loin is the area from the 13th thoracic vertebra to the first sacral vertebra. It is a segment of the spine consisting of the 7 lumbar vertebrae and their associated attached muscles.  It is the same part of the dog that  when taken from a hog, you buy as "loin of pork".  What they are describing may be termed the flank, but it cannot be termed the loin, because that term already has an anatomical definition upon which canine anatomists and hog butchers agree.  That name is already taken - and has been so for hundreds of years.

Some have described the loin as anything from 1 to 3.5 inches.  My question to you is - should a rather long-bodied mountain dog be rigidly or flexibly coupled?  If you say rigidly, then you are describing the short, rigidly coupled fox terrier type of body.  Some breeders have evidently been trying to change the apso to that style of body for years, but IMHO that is not  an Apso.

If you say flexible, then I want to know how much flexion do you think a dog with a 1 inch loin could have?  Or even a 1 inch flank? (since that seems to be the anatomical area that everyone has been referring to as the loin.)

The flank length will vary with the length and angle of the last two ribs. The loin is ALWAYS proportional to the length of the rest of the spine. Embryologically, the spine forms as one tube which then segments into the vertebrae and associated muscles.  These early segments are called somites.  See figure attached. There is no way to breed a dog to have long thoracic vertebrae and short lumbar vertebrae.  Therefore, if you have a rectangular dog (longer than tall) it will have a relatively long loin as well.  God made the rules - I didn't.

Furthermore, a very short loin would interfere with flexibility.  A long stiff dog would not be agile.  If the ribs are too close to the pelvis, the thoracic cage impinges on the pelvis on turning and flexing the body.  - Like a short-waisted human figure.

Finally, where does it say, in any standard, that the loin should be short? Where oh where did this myth arise?  I think I know - the same place the "short back" cult came from.  To its credit, the Canadian standard says, "LOIN: too long a loin adds excess length to the back and results in a loss of strength to the forepart of the body. If the loin is too short there will be a loss of flexibility."  While there is some question as to length causing a loss of strength, the latter part of this sentence is very obviously true.

Just grabbing the dog at the waist and estimating the distance between the end of the ribcage and the muscle of the upper thigh may give you a rough estimate of the length of the flank, but it is not a "measurement" of the loin length.  Please refer again to the textbook illustration of how to measure the loin, and read the accompanying legend.  The loin IS the 7 lumbar or loin vertebrae, easily measured by counting to 7 forward along the spine beginning with the easily palpable last lumbar, just in front of the pelvis.  Since this involves measuring easily palpated BONY landmarks, it is accurate as well.  It is extremely easy to feel the first and last lumbar vertebrae.  The shape of the spines is different from the thoracics and the sacrals.  Where even the slightest lateral curvature of the spine can throw a measurement of the flank way off, the midline measurement is always the same, and  there is minimal possible error.

We might ask "what is the point anyway"? The standard makes specific reference to the body height and length based on precise landmarks. Some standards give a measurement of the nose length as well. Since no standard even mentions a measurement of the loin, measuring it may not be worth the trouble. My mother always said "If it is not worth doing right, then it is not worth doing at all!"  I think she may be on target in this case. Since the apso standard does not request a particular length of loin, my only interest in the loin is to see if it is strong - as the standard states it should be.  But if for some reason someone wants to measure the loin, there is only one way to do it - the right way.

Can grabbing the waist be useful in telling whether a dog is "well ribbed up"?  Yes I suppose so.  The length of the flank may give some indication of the slant and length of the last few ribs, ("well ribbed up" implies relatively long terminal ribs) but that can better be estimated by palpating the ribs themselves..

I think that the "short loin" cult, like the "short back" cult is something which has crept into our notions of the breed, even though it exists nowhere in any standard, and is even refuted in the earliest standards:

"Body.  There is a tendency in England to look for a level top and a short back. All the best specimens have a slight arch at the loin and the back should not be too short; it should be considerably longer than the height at the withers. The dog should be well ribbed up, with a strong loin and well developed quarters and thighs." - Lionel Jacob, 1901

Notice that Mr. Jacob describes the loin correctly as the keystone arch of the  lumbar spine. There is no implication here of a short back or loin as being correct. He wants strength in the loin, and good development of the hind quarter. The idea that weakness is synonymous with length is erroneous. Long and thin might be weak, as would short and thin, but long and well developed may, for good reasons, be stronger than short.

There are good anatomical reasons for wanting good sized lumbar vertebrae, with resultant length of loin. The loin musculature is what provides the coupling for the rear drive.  The powerful muscles which originate on the lumbar vertebrae and last rib and insert on the pelvis are the rearing muscles - the psoas major and minor and the quadratus lumbricalis, assisted by the longissimus dorsi and the strong fascia of that muscle.  The amount of muscle in the loin will depend on the surface area upon which the muscle originates.  Less length and width of the vertebra, the less muscle you can have.  So it does not follow that length = weakness. THIS IS A MYTH.

This is what McDowell Lyons has to say about the loin:

" Between the thoracic section and the pelvis or croup, we have the loins, consisting of seven vertebrae.  These are longer and wider than the dorsal (thoracic) vertebrae and their spinous processes are short, thin and wide, being inclined forward to give better support to the action of the dorsal or rearing muscles in this vicinity.  This section does not receive support from the other bones in the framework but sets like a bridge or arch between the two business ends. ... The keystone arch should be sought in all breeds for the loin section, but generally this should not be greater than necessary to provide structural support.  If there is to be a deviation, let it be upward into a roach for those will not sag and become soft as quickly as a loin without any arch."

How many Lhasas do we see (even the very short backed ones) with tipped up pelves and sagging loins?  Everyone seems to fault a slight roach in the topline, and overlook the truly unsound sagging loin.  In the quest for the mythologic short loin, we can breed for miniaturization of the vertebrae - and some breeders may have accomplished this.  With it they have achieved sway backs, with weak and unstable musculature. Is this healthy?  Is this what a mountain dog needs to survive?

In summary:  We have found out where the loin actually is and how to measure it.  A short loin on a long dog is an anatomic oxymoron.  Nature does not manufacture the spine in pieces - either all the vertebrae are short, or they are all long.  The length of the flank depends on the length of the loin and the length and angle of the last few ribs. A well developed strong loin IS called for in every standard of the Lhasa Apso.  The size of the vertebrae (length and width) determines the amount of musculature of the loin.  It follows that small, foreshortened vertebrae will result in a weak loin, rather than a strong one.

So is there any merit to attemping to "measure" the loin?  the standard does not even mention it, so my answer is: If you want to measure it, do it right, otherwise measuring by cruder means is irrelevant. The length of the loin will always be in a fixed ratio to the length of the entire spine, so why bother?  If the dog is well balanced  with a broad, muscular, slightly arched loin, the loin length is correct.