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Managing young horses: based on Growth Plates.

Not Own Photo, in process of referencing/deleting.

There is always lots of debate as to when to back and ride young horses. As our knowledge of horse anatomy has improved, the reasons against starting early have moved to be based on when growth plates close. I think this is a good thing, as it shows that the industry is beginning to really accept science and use it to improve the welfare of horses. However, I think it is important for people to understand that knowledge of growth plate fusion is not just important for backing and riding away horses, but for managing them from birth.

What are growth plates?

For those of you who are not familiar with growth plates or growth plate fusion, a growth plate (epiphyseal plate) is a line of cartilage at the ends of the long bones. These areas are responsible for bone growth and development. Growth plate fusion, is when the bone stops growing and the cartilage growth plate fuses into bone. In horses, this process starts from the bottom up, with joints at the bottom of the legs fusing first.

When do Growth Plates close?

Understanding growth plate fusion and when it occurs in different parts of the body is vital for managing young horses. This is because, until fusion has taken place, we can change or control (to an extent) how the bone grows. Here are some tables of when areas typically go through fusion:

BoneFront LimbHind Limb
Inside HoofBefore BirthBefore Birth
Pastern6 Months6 Months
Fetlock Joint6 – 12 Months6 – 12 Months
Metacarpal/Metatarsal12 – 18 Months12 – 20 Months
Knee/Hock2 Years2 – 3.5 Years
Radius & Ulna/Tibia & Fibia3.5 Years3.5 Years
Elbow/Stifle3.5 Years4 Years
Humerus/Femur3.5 Years4 Years
Scapular/Pelvis4 Years5 Years
A rough overview of when Growth Plate Fusion has typically finished in the limbs
Bone/AreaWhen Fuses
Neck3 Years
Jaw5 Years
Back (behind the withers)6 Years
Withers6+ Years
Atlas & Axis (Bones joining neck to head)6+ Years
A rough timeline of when other areas of the body go through growth plate fusion.

Affecting bone development

Being able to affect bone growth is usually seen as a negative thing linked to training horses too young. Many racehorses are started before 2 years of age and many go on to have problems with their back in later life, such as kissing or rotated spines and misaligned pelvic problems. This can be related to the fact that they are having weight on their back up to 5 years before their spine has stopped growing.

However research has also suggested that while starting racehorses young puts them at risk of back problems in later life, it can protect their limbs from serious injury during their racing career. So when it comes to racehorses, understanding growth plates can both help and hinder the horse.

Many horses are born with conformational limb deformities, such as pigeon toe. Although these problems can be improved by remedial trimming and shoeing, if this problem is addressed while the growth plates are still open, there is a good chance of correcting the problem for good. Therefore a better knowledge of growth plates can help improve the quality of our horses.

I was lucky that the stud at University used a lot of remedial trimming, sometimes shoeing the young horses they produce. I have been able to see first hand the before and after results, and understand that if action had not been taken, the problem is often likely to get worse before growth plate fusion, due to the pressure on the bones.

There really isn’t an excuse for young horses to have terrible leg confirmation any more. You should be only be breeding from good quality animals and we should be improving on any limb confirmations while they are young. Not only does this make them better riding horses, capable of more athletic jobs, but it will also help keep them sound and comfortable for longer. More breeders should be embracing the knowledge of growth plates to improve their young horses, rather than just turning them out in the field and hoping for the best.

Last Updated on 04/05/2022

2 thoughts on “Managing young horses: based on Growth Plates.”

  1. Pingback: Thoroughbred growth rates: Ready to Race? | EquiPepper

  2. Pingback: New Season – New Start | midwest endurance rider

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