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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

General Update

I just wanted everyone to know that I’ve been a bit busy recently with some RL stuff.  Nothing to worry about, so no need to send me condolences or flowers, but canolis would be greatly appreciated thanks to blondemare for getting me hooked on them.

I am about half done the first hind limb conformation article and am expecting to have it completed and up before the end of this week.

Thanks to everyone for being patient, and of course for your continued support and participation.

Merc

The Bad And The Ugly – Halter Horses

For some strange reason I was under the impression that QH Halter horses had moved away from the muscle bound, post-legged creature when HYPP was confirmed to follow these horses’ bloodlines; that breeders immediately tested all their stock and culled (or at least stopped breeding) those positive for the genetic marker. I was wrong. Thank you to Steph C for making me ill.

Here is a nice, little summary of what took place and when concerning the AQHA and HYPP horses: http://www.aqha.com/About/Content-Pages/About-the-Association/Services/HYPP.aspx

From that AQHA report the QH breeding industry has had factual knowledge of HYPP for over TWO decades. Then why is this breeder standing TWO HYPP N/H ‘Champion’ Stallions? (Don’t forget to look at the broodmare page!)

In fact, I want to know why the AQHA would even allow a HYPP N/H individual (stallion or mare) to be eligible for what is essentially a ‘breed’ title, when they clearly recognize it as an undesirable genetic defect. After all, are halter horses not supposed to be the epitome of the breed, displaying true and pure breed characteristics derived from solid genetics?

From the interview of Dr. Sharon Spier in the AQHA link I provided, she said: “Impressive had numerous qualities, including excellent conformation, which gave him tremendous success in the halter ring.”

That led me to go looking for a picture of Impressive to see if her statement was true. Here is a picture of Impressive later in life.

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He certainly had some great conformation features;

  • Excellent length of hip
  • Good LS joint placement
  • Medium back
  • Excellent length of humerus bone
  • Medium neck length
  • Medium neck set
  • Deep, wide loin
  • Short cannon bones
  • Medium pasterns

On the weaker side of things, his ribcage didn’t carry back particularly well and his loin was longish.  His shoulder angle is a bit closed, he’s tied-in below the knees, and he doesn’t carry enough bone for his size.  While he’s straighter behind, he’s not post-legged.

At first I thought he was bull-necked, but looking at the odd and over-developed muscling behind his ears and throat, the lack of crest muscling and the line of muscling directly in front of the shoulder indicates that he hurt his neck at some point, such that the bull-neck posture is likely pathological.  The over-development of croup muscling is also likely from injury, particularly when we also consider the flat and angular loin.

And yes, he’s got quite a lot of muscle mass, which was one of the main reasons he was used for halter horse breeding.  It isn’t, however, grossly over-exaggerated like we see now in halter horses.

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Let’s take a closer look at one of this breeder’s champion stallions to compare conformation that is winning in the ring today.

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On the positive side, this stallion and the rest of the breeding stock (mostly) possess quite nicely structured and set necks of appropriate length.  Most have maintained medium backs; all have big hips and well placed LS joints, and loins of depth and breadth.  We also see the croup muscling coming forward and being full over the loin and into the back, that’s quite good.

While Impressive had a bit of a laidback shoulder, this stallion’s is quite laidback.  The shoulder angle, though, is a bit closed.

Like this stallion, most of the horses possess a steeper pelvis than Impressive, but body balance is similar being slightly downhill. This horse’s face is really too short.

The real big issues for these halter horses are the lightness of bone and the excessive post-leggedness.  The latter in this case causes the horse’s hamstrings and associated soft tissue to be attached too high and be too tight.  This (excessive post-leggedness) should be a deal breaker, all day long, every day, for ANY horse regardless of discipline, and when you combine that trait with joints that are too small and a massive body above you’re, at the very least, out of your mind to perpetuate it as a breeder.

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There’s absolutely no reason why halter horses can’t have conformation conducive to proper equine function.  There’s even less reason for why they shouldn’t.  Even if they never carry a rider, they should be able to do so at a higher level and stay sound doing it.  These halter horses do possess some really fine equine qualities.  It makes no sense to breed in and keep serious faults and genetic defects that are detrimental to health, soundness and longevity.  If people do so with the knowledge of what they’re doing, I have nothing good to say about them as stewards of horses, and if they do so out of ignorance; “Get a clue, people!”

Saddle Seatbelts

Known facts:

Seatbelts in cars save lives.
Riding horses carries inherent risk.
People fall off horses all the time and injure themselves, some fatally.

Pulliter System

Is having a seatbelt system like the one linked above a good or bad idea?

Comments are also welcome.