It’s spring in Florida and that means my docs are out checking new foals to make sure they’re healthy. With their long, awkward, spindly legs, it’s a wonder any foal can ever stand up and run around, but they seem to accomplish it somehow. No foal is a match for my feline elegance, but sometimes, a foal is born with legs more crooked than usual, or his legs become that way over time. If you’ve got a foal around, it’s really important for you to know what to look for in limb conformation. What you do now to take care of your new foal can set him up for success (or potential crippling lameness problems) for the rest of his life. Crooked foalsYeah, no pressure! The good news is my doc can fix a lot of these issues if they are identified in time. Now let’s talk about what we mean by “crooked foals”.

There are 2 major categories we’ll discuss: Angular limb deformities and flexural limb deformities. I know those names are kind of intense, but here is a super basic breakdown: an angular limb deformity looks crooked when viewed from the front, while a flexural limb deformity looks crooked when viewed from the side. There are different causes and treatments for each of these, so let’s look at them a bit closer. This week we’ll talk about Angular limb deformities, and we’ll go over flexural limb deformities in part 2.

Angular limb deformities (ALD)

An ALD is an inward or outward deviation of the leg from midline, when viewed from the front (or back) of the foal. We call an outward deviation “valgus” and an inward deviation “varus”. Then we add the name of the joint at which the deviation starts. So for example, if you’re looking at a foal from the front and his legs are straight until the knee (carpus), then the lower legs deviates outward, he would have a “carpal valgus”.

It’s not uncommon for a foal to have a mild “knock kneed” appearance at birth, but it’s really important to have an exam by a vet to ensure that it’s not a conformation problem that is going to extend into adulthood. This type of deformity can have several different causes, some present when the foal is born and some developing over time. The treatment is very different depending on the cause, so you’ve gotta have my doc out to find out what the underlying problem is. Here are several potential issues:

• Incomplete ossification of the cuboidal bones

During gestation, the small bones in the foal’s carpus (knee) and tarsus (hock) turn from cartilage into bone. We call them cuboidal bones since they’re roughly shaped like little cubes.  Normally, these bones are fully turned to bone (ossified) by the time the foal is born. If the foal is born premature, or the mare was sick during pregnancy, or for one reason or another the baby doesn’t “cook right”, those little cuboidal bones are still cartilage when the foal is born. Here’s the big problem with that – cartilage is much softer than bone and not meant to support the foal’s weight through the joints. If there is only soft cartilage where bone is supposed to be, it can be crushed by the foal standing and moving around on it. Once it turns into bone, it will be fixed in whatever shape it was deformed into, dooming the horse to joint pain and lameness on a malformed joint. So we really have to start working on these cases immediately – you really don’t want to wait long before calling my doc to have a look! Foals that have signs of prematurity should have x-rays taken of their knees and hocks to make sure the bones are fully developed into bone. If incomplete ossification is found, the foal will need his legs splinted and to stay resting in the stall. My doc will take x-rays at intervals to check when the bones have formed. Once the bone is there, the foal will be allowed to resume more normal activity. If we can keep the bones from crushing, they will ossify over time and the prognosis is good.

Normal  ossification of the bones in a foal’s carpus

 The bones of this carpus are incompletely ossified – that’s why they don’t show up on this x-ray.

See the crushed bone in this hock? You don’t want your foal’s hock to end up looking like this!

• Laxity of ligaments around the joint

Sometimes the ligaments that hold the joint straight are a bit too loose when the foal is born. My doc might notice this when she manipulates the joint. She would be able to manually straighten the leg, but when the foal stands on it, it becomes crooked again. If she takes an x-ray and is satisfied that those cuboidal bones aren’t the problem, that’s probably good news, since ligament laxity will usually improve in time. Controlled exercise and growth of the foal will usually resolve this problem.

• Disproportionate growth

This is the most common cause of angular limb deformity and can be caused by unbalanced nutrition, excessive exercise, or overload of the limb, which damages the growth plate. As the foal grows, one side of the leg increases in length faster than the other, resulting in an angular limb deformity that develops over time. My doc has several tools at her disposal to influence the rate of growth to correct the imbalance so that the limb will straighten up over time. The trick is she has to be able to do this while the growth plates are still active. Different growth plates close at different times, and for some joints (especially the fetlock) we have to act sooner than others. Unfortunately, if you wait too long to call my doc and the growth plate has mostly closed, there isn’t a whole heck of a lot she can do. For the fetlock, we have to act before the foal is 2-3 months old, so don’t mess around!

For a foal that is only mildly affected, therapeutic trimming of the hoof and glue-on shoes may be enough to help the foal stand more correctly and encourage the joints to align correctly. For a more significantly affected foal, a surgical procedure called a “periosteal strip” (aka “periosteal transection and elevation”) can be used to stimulate the growth rate on the side of the limb that is lagging, helping it to catch up to the other side. However, in situations where the foal is more severely crooked or when there is not much time left until the growth plate closes, a procedure called a “transphyseal bridge” may be needed to correct the deviation. This involves temporarily placing a metal implant across the growth plate to slow the rate of growth on the side of the leg that is growing faster, allowing the opposite side to catch up. The implant is usually one screw or two screws with a wire in between. It will be removed when the foal’s leg has straightened.

This screw is used as a transphyseal bridge to show the growth on that side of the limb so the opposite side can catch up.

You’ve waited a long time for your foal to be born, so give him the best start by having him evaluated at regular intervals. My doc will make sure those legs are growing nice and straight and help you avoid CAT-astrophe!

Until next week,

 Tony

PS – Don’t forget to check out our podacst page. It is filled with tons of knowledge. I am quite certain you will learn something new!