|X-Rays & the Prepurchase Evaluation
studies (x-rays) have become an integral part of the equine
evaluation. Potential horse buyers commonly
request x-rays as part of the veterinary inspection process.
And, as you know, many horses have “failed” examination
based on radiographic findings, such as bone spurs in the hocks
or enlarged channels in the navicular bones. But have you ever
wondered exactly what information radiographic studies provide
the horse buyer?
First of all, we must realize that radiographs (x-rays) reveal
only one small part of the whole picture. Radiographs provide
structural information; in other words, they
tell us what things look like. More specifically, they tell
what bone looks like. Since soft tissues all have a similar density
on x-ray film, we often don’t get a lot of insight into
problems that effect tissues such as tendons, ligaments, muscles,
synovial membranes, etc. Therefore, a normal radiographic study
doesn’t confirm normal/ healthy soft tissues.
Secondly (and more importantly), the true source of pain and
lameness (i.e. inflammation) is radiographically invisible.
In other words, we can’t “see” inflammatory
cells on x-ray film. What we can see are potential effects that
inflammation may or may not have on associated bony structures.
Therefore, the normal radiographic appearance of bone
does not confirm the absence of active inflammation. Likewise,
the abnormal appearance of bone does not always confirm the presence
of active inflammation.
This is especially true in low-motion areas, such as the distal
tarsal (hock) joints and the navicular region. Ironically, most
horse buyers request radiographic studies of these two areas before
It is not to say that radiographic examination does not provide
the veterinarian with valuable information and that taking x-rays
is a waste of time. It is very important to know what bone looks
like, especially in suspect areas. However, since there is poor
correlation between what is observed radiographically (i.e. what
the tissue looks like) and what is observed clinically (i.e. what
tissue acts like), the veterinary examiner must be careful during
interpretation of the x-ray study (especially when assessing low-motion
It is not
uncommon the hear of a sound horse “failing”
a prepurchase exam due to abnormal radiographic findings, only
to watch it perform beautifully for years to come. Likewise,
it is not uncommon to hear of a lame horse “passing” prepurchase
examination due to normal radiographic findings, only to watch
the new owner invest a lot of time and money in trying
to diagnose and treat the lameness.
veterinarians tend to be hesitant to make recommendations that
conflict with radiographic findings, especially if they
abnormal. This is undoubtedly one of the repercussions of our
current legal system. However, it is very important that the
buyer understand exactly what information is contained within
the radiographic study so as not to disregard the veterinarian’s
In our opinion,
the horse buyer should have specific reason(s) for requesting
radiographic examination of a horse, rather
than just to see what “shows up”.
The Atlanta Equine Clinic recommends prepurchase radiographic
evaluation under the following circumstances:
1. If the client wants “baseline” studies
that will allow for future radiographic comparison of certain
If a horse develops lameness, for example, as
a result of a sore joint 5 years after purchase, it would be nice
to know what osseous (bony) changes have occurred in that joint
since the time of purchase. Veterinarians can more accurately assess pathologic conditions in bone and joints through the
process of image comparison. By taking images at the time
of purchase, we are assuring our- selves the luxury of comparative
interpretation in the case that a future problem arises. This
is better, of course, than passing judgment on a lesion based
on a single radiographic study.
developmental orthopedic disease (DOD), such as osteochondrosis,
In young horses particularly, there is often concern that a manifestation
of DOD is present. The most common manifestation of DOD is osteochondritis
dissecans (OCD). Since many OCD lesions are subclinical (i.e.
do not result in swelling or lameness), the veterinarian may
not be able to detect their presence based on clinical evaluation
alone. In these cases, radiographic examination would be indicated
to determine if such lesions exist. This is sometimes referred
to as an “OCD hunt”, since there is often no preconceived
notion as to what might show up. Since DOD lesions can eventually
become clinically apparent (i.e. eventually cause lameness),
radiographic presence may be considered significant in regard
to future performance of the animal. Exactly how the lesion(s)
might affect future performance depends on their type, size,
location. It is important to realize that the only way to
confirm that there is no evidence of DOD is to radiograph every
joint in the horse’s body. Since this is generally
not practical, the veterinarian usually selects the 2-3 most commonly
affected areas to study.
clinical evidence of inflammation is evident in a high-motion
There is much better correlation between clinical and radiographic
impressions of high-motion versus low-motion joints. Therefore,
the presence of radiographic lesions in high-motion joints can
provide us with invaluable information concerning both the degree
and duration of a problem. One could accurately predict, for example,
that if significant bony abnormalities are visible radiographically
in a high-motion joint (such as the fetlock joint), that there
will likely also be some clinical abnormality (such as a positive
flexion test). This is not always the case with lower-motion areas,
such as the distal tarsal (hock) joints.
resale value of the animal is important to the client.
As most of us know, ugly x-ray studies have and will continue
to adversely affect the sale of horses. Even though we’ve
determined that not all radiographic abnormality means poor performance
and not all radiographic normality means good performance,
what specific joints look like might be important when it comes
time to sell the horse. Just remember, the results of an x-ray
study provide a lot of information... we just need to be careful
how we interpret the information.