By Dr. Deb Bennett:

"Owners and trainers need to realize there's a definite, easy-to-remember schedule of fusion - and then make their decision as to when to ride the horse based on that rather than on the external appearance of the horse. For there are some breeds of horse - the Quarter Horse is the premier among these - which have been bred in such a manner as to LOOK mature long before they actually ARE mature. This puts these horses in jeopardy from people who are either ignorant of the closure schedule, or more interested in their own schedule (for futurities or other competitions) than they are in the welfare of the animal.

The process of fusion goes from the bottom up. In other words, the lower have fused; and the higher up toward the animal's back you look, the later. The growth plate at the top of the coffin bone (the most distal bone of the limb) is fused at birth. What this means is that the coffin bones get no TALLER after birth (they get much larger around, though, by another mechanism). That's the first one. In order after that:

2. Short pastern - top & bottom between birth and 6 months.

3. Long pastern - top & bottom between 6 months. And 1 year.

4. Cannon bone - top & bottom between 8 months. And 1.5 years.

5. Small bones of knee - top & bottom on each, between 1.5 and 2.5 years.

6. Bottom of radius-ulna - between 2 and 2.5 years.

7. Weight-bearing portion of glenoid notch at top of radius - between 2.5 and 3 years.

8. Humerus - top & bottom, between 3 and 3.5 years.

9. Scapula - glenoid or bottom (weight-bearing) portion - between 3.5 and 4 years.

10. Hindlimb - lower portions same as forelimb

11. Hock - this joint is "late" for as low down as it is; growth plates on the tibial & fibular tarsals don't fuse until the animal is four (so the hocks are a known "weak point" - even the 18th-century literature warns against driving young horses in plow or other deep or sticky footing, or jumping them up into a heavy load, for danger of spraining their hocks)

12. Tibia - top & bottom, between 2.5 and 3 years.

13. Femur - bottom, between 3 and 3.5 years.; neck, between 3.5 and 4 years; major and 3rd trochanters, between 3 and 3.5 years.

14. Pelvis - growth plates on the points of hip, peak of croup (tubera sacral), and points of buttock (tuber ischii), between 3 and 4 yrs.and what do you think is last? The vertebral column, of course. A normal horse has 32 vertebrae between the back of the skull and the root of the dock, and there are several growth plates on each one, the most important of which is the one capping the centrum. These do not fuse until the horse is at least 5 1/2 years old (and this figure applies to a small-sized, scrubby, range-raised mare. The taller your horse and the longer its neck, the later full fusion will occur. And for a male - is this a surprise? -- You add six months. So, for example, a 17-hand TB or Saddlebred or WB gelding may not be fully mature until his 8th year -something that owners of such individuals have often told me that they "suspected").

The lateness of vertebral "closure" is most significant for two reasons. One: in no limb are there 32 growth plates! Two: The growth plates in the limbs are (more or less) oriented perpendicular to the stress of the load passing through them, while those of the vertebral chain are oriented parallel to weight placed upon the horse's back.

Bottom line: you can sprain a horse's back (i.e., displace the vertebral growth plates) a lot more easily than you can sprain those located in the limbs. And here's another little fact: within the chain of vertebrae, the last to fully "close" are those at the base of the animal's neck that's why the long-necked individual may go past 6 years. to achieve full maturity). So you also have to be careful - very careful - not to yank the neck around on your young horse, or get him in any situation where he strains his neck."

(Follow-up piece to Bone Fusion Schedule)

"That being said, even if the trainers do not use chemicals to sore horses having horses on stacks is harmful in and of itself. Mechanical soring happens because the big lick horse has to travel with more than 50% of its weight on the hind end which the back and hind legs were never designed to do. This will result in arthritis in the hind legs and in particular the hocks. Second, the weight of the pads is supported fully by the front legs (don't buy that business about so many ounces over the entire weight of the horse-according the laws of Physics, it is completely false!)

The front legs of the horse are not attached to the skeleton through any kind of bony attachment. Only muscle, ligaments and tendons hold the front legs on to the rest of the horse. These muscles, ligaments, and tendons attach into the spine at the neck. Starting immature horses (under five or six) in pads increases the stresses on the incompletely formed vertebrae and can lead to wobblers (in case you were wondering why so many TWH have wobbles and why TWHBEA says its not inherited). The other thing is that the natural breakover point of the hoof is delayed far beyond the time it was designed to break over. There is a suspensory apparatus in the leg whose function it is to pick the front leg off of the ground as the horse travels forward. This is done mechanically with little to no muscle involved. Now delay the breakover and the suspensory apparatus is over-ridden and the horse has to use the muscles in his neck and shoulder to pick up the leg. This means using the muscles in a fashion they were never intended to be used. The muscles get sore as well as the insertion point of the muscle exerting forces on the bone (that it was not intended to take) which results in muscle tears and arthritis. The other thing is that even if the horse is not chemically sored most padded horses are trained and shown in action devices aka, chain. Not the legal 6 oz. chain either but heavy chains that are going to hurt. Why? Because if you put something on a horse's pastern that does "not hurt" they will walk funny for about 10 minutes and then forget about it. So it doesn't work to train with action devices unless you are willing to inflict pain.

In conclusion, if a trainer really KNOWS horse anatomy and physiology he will either:

1.) not pad and not delay the breakover point or

2.) decide that the future well being of the horse is not as important as this week's paycheck and will ignore what he knows is harmful.

And then there is option 3.) which is that the trainer learned about horses 30 years ago (for about a week) and hasn't learned a thing since then."

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Altho the above was directed towards the TWH industry, you can see that it applies to Icelandic Horses also. Whether or not there is actual chemical soring, there are still problems with weighted shoes and road founder in enhancing front end action.

Detrimentally, what wins in the show ring, is the future of the breed.