The Up And Down Of It – Hind Limb – Part 1 (Addendum Added-2/25/14)

Even though we are discussing the hind legs last, they are of singular importance. Along with the pelvis, they decide how a horse is ‘geared’; high revs with a short stroke for sprinting, or lower revs with a longer stroke for dressage – and everything in between.

The LS joint is the upper most joint of the haunch, not the hip joint, and covers only about six inches of surface area. It joins the horse’s entire hindquarter to its ribcage (and thusly to its front). Think about that for a moment, the entire haunch is attached to the rest of the horse by an area the size of your hand. It’s why the loin and sacrum are often the first areas of stress and injury in the horse.

It’s important to understand how the whole haunch works as one. Tendons and muscles that run parallel with the horse’s bones create a ‘stay system’ that coordinates the opening and closing of the joints:

  • If the stifle joint closes then the hock joint also closes, or if the stifle joint opens then the hock joint also opens
  • If the loin coils (via the LS joint) then the stifle joint closes, or if the loin flattens (via the LS joint) then the stifle joint opens

There is no way around the stay system without causing damage to the horse. It should now become apparent why such traits as table top croup (overly flat pelvis), post-leggedness (overly straight hind leg causing open joints) and over-angulation (overly crooked hind leg causing closed joints) are serious faults in the horse.

Table Top Croup

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We can see that the flat croup of this horse causes the femur to be positioned quite vertical (indeed, in a vertical position associated with a racehorse in full extension – see diagram), in turn creating a very open stifle angle of approximately 143 degrees. Imagine the amount of loin coiling that would need to happen for this horse to lower the haunch for collection.  The fact is the LS joint doesn’t have that kind of range of motion. Conversely, imagine what happens if this horse flattens its loin just a little, how that will put the femur completely vertical and further open an already open stifle joint, stressing it.  This horse is functionally post-legged in the upper half of his leg and it would not be a surprise if he suffered from sticking stifles.

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Post-legged

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Our post-legged horse has a much steeper pelvis and it’s a good thing as it puts his femur far less vertical than our first horse making a stifle angle of 130 degrees. If he had a more typical pelvic slope he’d be overly open in this joint, but as it stands he’s already got enough problems. His hock angle is a whopping 160 degrees. Note the racehorse below in full hind leg extension (via fully flattened loin and fully opened stifle) only has a fully opened hock angle of 160 degrees. The horse’s hock doesn’t, and isn’t supposed to open to create a perfectly straight leg. That means that if this horse flattens its loin just a little, which has to happen as part of normal striding, his hock will be pressured to hyperextend.  The horse will try and protect himself by taking itty, bitty steps behind.

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Over-angulation

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This horse has a steeper pelvis as well, but also the most horizontal femur because she’s standing with the leg too far underneath herself artifically closing the thigh joint. Of course, because of the stay system that also artificially closes the stifle and hock joints. Despite that we can still clearly see that over-angulated hind legs possess more closed joints; 115 degrees for the stifle and 140 degrees for the hock – adjusted 5 degrees higher for a properly aligned stance behind nets 120 and 145 respectively. Horses built like this live with joints perpetuately a bit closed, which comes with its own stresses (and possible injuries – ie. curbs). Opening the joints would relieve those stresses, but because of the stay system the horse would have to flatten its loin along with the opening of those joints, and now you’ve got a hollow horse with trailing hocks.

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For comparison sake, below are a hind limb suited to dressage and a hind limb suited to racing.  Pelvic slopes are very similar, and though the dressage leg is more angulated, and the racing leg straighter, we’re not talking gobs of difference between a horse that can piaffe in her sleep and a racehorse who thunders down the track in excess of 35mph.

I included a second racehorse hind limb to look at, Secretariat.  He had a steeper pelvis (about 5 degrees) than the dressage horse, but note again that the angles created are not hugely different.  This should make it obvious to all, that extremes like the examples above are bad for horses and should not be perpetuated.

Lastly, take note the difference of femur to tibia bone length ratio in the dressage horse vs the femur to tibia bone length ratio in the racehorses.  That is a key factor in ‘gearing’ and will be discussed in more detail in a subsequent article.

Dressage Hind Limb

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Racing Hind Limb

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Secretariat

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jrga made an excellent suggestion that I also mark the hind leg of the second racehorse in the racing picture to show maximum folding (closed joints) of a properly constructed equine leg as a comparison to the fully extended (open joints) of a properly constructed equine leg.  So here is that picture remarked.  Of special note is that the pelvis and tibia become parallel, and the femur and cannon bone become parallel as a result of full and proper coiling of the LS joint.  It can not happen this way for horses with non-concurrent hind limb angles, or a table top croup. 

Horse-racing-3 - Hind Leg Marked - Both Horses

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The Long And Short Of It – Part 1 – Hip/Pelvis

Conformation is an extensive topic and many get overwhelmed.  To help make it easier to digest, I’m going to break things down into really small chunks and hope that prevents choking on the technical data. 

Following is part one of three discussions on the length of the hip, back and loin, respectively, and what that means to the horse.  For clarity and comprehension sake assume the discussion is always about ‘riding’ horses, as opposed to ‘draft’ or ‘racehorses’.   Many aspects will apply to the latter two as well, but there are also exceptions.  I will periodically make mention of those exceptions, but for everything else go with ‘this applies to riding horses regardless of discipline’.

As mentioned in the article ‘To Plow Or Not To Plow’, hip length is important for power potential; the more length, the more power potential.  This potential is based on two principles; more length for muscle mass, and more length for leverage.   There is no such thing as a ‘too long’ hip in equines, but there certainly is ‘not having enough length’

The horse needs to possess power to perform tasks.  Arguably, some tasks require more power than others, but it also takes power to engage and collect and while we don’t need every horse to collect to the highest degree, we do need them to engage to protect themselves and perform even the simplest tasks correctly and well.

I’m going to use the same set of horses for all three parts of this series.  I’ve randomly picked individuals from sale ads; some from www.dreamhorse.com/ and some from www.equinenow.com/

  • Poor hip length: < 30%
  • Average/Adequate hip length:  30-32%
  • Good hip length:  33%+
  • Great hip length:  35%+

To determine hip length we measure the horse’s body length and divide that number into the hip length number to arrive at a percentage. 

  • Body length is measured from point of shoulder to point of buttock. 
  • Hip length is measured from point of hip to point of buttock.

Here is a picture of the horse’s skeleton with the three points marked (in red) so you can see where to find the bony points.  Palpating your own horses will improve your ability to spot the points on other horses without touching.  It is harder to see these points when covered in flesh, and even harder sometimes in photos.  We often use differences in lighting and shading to spot the points in photos.

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Horse #1 – 10yr old QH Stallion

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Because of the amount of muscle and how smoothly it ties from one body part to another it’s more difficult to see the points, particularly the point of shoulder.  There is a shading difference and a ‘wrinkle’ in the skin/muscle that helps us find the point of hip.  Being even a bit off in the points can greatly affect the measurement from a photo.  When the eye gets good enough you no longer need to get out the ruler and protractor to have a real sense of the horse’s proportions, ratios and angles.

Below I’ve marked where I believe the points to be.  Now measure body length and hip length and divide the hip number by the body number to come to a percentage.

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My measurement comes to a hip of just under 36.5%.  Our figures are going to vary a little bit depending on how big (or small) the diagram is on our screens and how accurate we each are at measuring from point to point, but we should all be getting a hip figure that clearly states this horse has ‘great’ length of hip.

Horse #2 – QH Gelding

The roaning on this horse makes it a bit harder to see the point of hip, but he’s got a little dark speck right on the front edge of it.  The point of shoulder is easier see.  Now, before you peek, does this horse appear to have as much hip length as the first horse, or less?  If less, do you think he’ll still fall in the ‘great’ category?

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My measurement on this horse’s hip is a bit under 35%, so not as generous as horse one, but certainly a quite good length of hip.

Horse #3 – 4yr old QH

This horse has lots of smooth muscling on his haunch, especially pants muscling.  His pelvis is steeper, but does it have length to it?  Does it possess ‘good’ length?  His front end muscling is very muddy, so seeing the point of shoulder is difficult.

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I measure about 34.5%, so another one with a quite good hip length.  Don’t get fooled by a steeper pelvis that at quick glance can appear short.  Quarter Horses get knocked for some disastrous traits purposely bred into them over the years (and we’ll get to those at some point down the road), but one area where they rarely fail is in pelvic length.

Horse #4 – Arabian Stallion

It’s really easy to see the point of shoulder and buttock on this horse.  The point of hip is a bit harder, but there’s a darker spot of shading that helps us locate it.  Now that we’ve seen three very good lengths of hip, what is your first impression about this horse?

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This one is about 31%, falling in the adequate/average category.  It’ll get the job done for the horse, but he isn’t going to be setting the world on fire in the power department.  He’s a much lighter built horse, and this is not a breed we think about for pure power but they have been praised for their speed.  Speed develops from power potential, though, so this one is not going to be particularly fast for his breed. 

There is one thing to take special note of; this horse possesses what is termed ‘table top croup’.  This is a significant fault in a horse as it makes engagement and collection more difficult to achieve.  With the pelvis so flat, the natural tendency will be for hollowing the back, trailing the hocks, and high-headedness.

 Horse #5 – TB Gelding

So what are your first impressions about this guy’s hip?

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If you thought, ‘well, that doesn’t look like a very good length of hip’, then you were right.  This guy has about 29% and that is poor.  He does possess two ‘saving graces’.  One of them is an exceptional lumbo-sacral joint placement.  This is a situation where a trait or group of traits can significantly balance/nullify/make less weak a poor trait.  The second ‘saving grace’ will be discussed in Part 3 of this series.

Horse #6 – Paint Mare

So, what do you think about this mare’s hip length?

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If you guessed adequate/average then you were right.  She’s about 31%, same as the Arabian stallion.  I suspect, though, that some of you thought she fell into the poor category as the TB gelding before her. 

We’re going to talk more about this one in Part 3 of the series as well, since this horse – even with the better hip length – is a far weaker individual than the TB gelding with the poor hip length.  This is a case exactly opposite to that of the TB gelding; here we have a horse that possesses a faulty, but highly significant trait, which overrides many good traits and makes the entire individual weak.

Take a look in your barn and around the Internet and test your eye.  Look at hips and guess at their length then take the time to find the points and measure to confirm or correct your estimations.  It’s the only way to develop your eye.