Making a Diagnosis

Is your horse lame? Learn why it’s important to do what it takes to make an accurate

diagnosis you treat.

When I entered equine practice 30 years ago, I got my schedule from the office at the beginning of the day, then checked in when I had finished my appointments. I carried a beeper, and when I got a page, I had to stop at a convenience store along my route to use a pay phone. If I had to take radiographs, I developed them at the end of the day by dumping them in vats of chemicals in the practice darkroom. If I needed more or different views, I had to go back to the farm to repeat the process. Diagnosing a lameness was tricky, and chances were a horse would be treated based on a “likely guess” about what was wrong. Sore hocks? Inject them with corticosteroids and see if that helps. Sore feet? Talk to your farrier about corrective shoes.

Times have changed. These days, my cellphone is always at my side. My office can reach me any time they need me, and so can my clients. The beeper is long gone, and I haven’t seen a pay phone in years. I can take as many radiographs as my heart desires on the digital system, and if I don’t like what I see, I can simply repeat the view—right then and there. I honestly don’t know how any of us did it “back in the day,” but I do know things are better now. Technology has not only improved on the things we use every day, it’s also opened up a whole new world of tools for diagnosing lameness, and has led to treatment options that increase the chances for a successful outcome.

If you’ve had horses forever, you may long for the day when things were simple and wonder if it’s really necessary to do all of those things your vet recommends when your horse comes up lame. Yes it is, and in this article I’m going to show you why. I’ll look at three common scenarios where a lameness might not be exactly what it seems, and show you how making assumptions and treating the wrong thing is likely to be unsuccessful. Not only that, you’ll see how making a bad decision because you didn’t have a diagnosis can be downright dangerous for your horse.

The Signs:

My Aching Feet!

Your horse has always started out a little bit stiff and is sensitive to shoeing changes, but otherwise he’s been pretty sound—until last week when he had an obvious head nod. Your vet came out to do a lameness exam and saw that your horse was exhibiting a right front lameness that seemed more pronounced when longeing on a circle to the left. He trotted off lame when your vet flexed the lower joints of both front legs, and when your vet performed a nerve block that eliminated sensation to the back portion of your horse’s right front foot his lameness disappeared and shifted to the left side.

Does your horse have navicular bone issues? Or could he have a soft tissue injury in his foot? In times past, a foot-origin lameness that blocked to the heels might have been labeled navicular disease and treated accordingly—with corrective shoeing, pain relieving medication and possible corticosteroid injections in the coffin joints. Now we know that it’s not that simple. There are many different structures that can be injured within the foot and successful treatment depends on identifying the underlying problem.

The Question:

The next step in any diagnostic work up of a

Diagnostic Dilemmas:

lameness that blocks out in the foot is taking radiographs, and obvious signs of navicular bone degeneration can help identify the bone as the source of pain. Radiographs can also provide clues about soft tissue structures that might have been injured where they attach to bone. Unfortunately, ultrasound examination to assess the soft tissues of the feet is challenging because the hoof wall makes it impossible to assess structures deep within the hoof. Magnetic resonance imaging (MRI) has become the gold standard to diagnosing foot-related lameness because it provides a detailed look at both bone and soft tissue structures.

Optimal treatments for foot-related lameness varies widely, depending on the specific structures involved. For example, corrective shoes applied for a horse with navicular bone or bursa problems will be completely different from those recommended for a collateral ligament injury. And while soft tissue injuries might be treated with injections with a regenerative therapy such as platelet rich plasma (PRP) to help encourage healing, bone problems might warrant bisphosphonates that target bone inflammation and pain. Without a specific diagnosis of the structure(s) involved, treatment decisions can only be made with a best guess approach.

Many foot-related problems will improve with corticosteroid injections in the coffin joints. So why not start by injecting your horse’s joints? If your horse has a soft tissue injury within the foot and you inject his joints, he’s likely to feel better. If you put him right back to work, there’s a good chance that soft tissue injury will get worse. If the work is hard and your horse no longer feels pain, he might even experience a catastrophic injury that could threaten his career.

If an MRI simply isn’t in your budget, you can safely make a compromise and inject his joints if you take care to exercise him very lightly for a minimum of 30 days. If the lameness reappears after that period of time, you’d

Why it Matters:

be wise to consider taking further steps to pin down a diagnosis before continuing to treat.

The Signs:

Not Quite Right

Your horse has been feeling “not quite right” behind for several months, and it’s getting worse. Your veterinarian performs a lameness exam. She determines that your horse is lame on the left hind leg, and that he has a positive flexion response to the middle joints of the both hind legs. He’s also sensitive to palpation of the area just below the left hock where the suspensory ligament originates.

Does your horse have hock arthritis or a suspensory ligament injury—or both? In times past, if your horse flexed off in the middle joints of his hind legs, there’s a good chance your vet treated your horse’s hocks with corticosteroid injections and sent you on your way. Now we know that hock problems and hind suspensory ligament issues commonly go hand-in-hand, and it’s important to know the difference.

Diagnostic blocks of the hind legs can be difficult (and dangerous!) if a horse resents the placement of needles, and distinguishing between hock and suspensory pain with blocks is complicated by the fact that there can be crossover between the responses of these two structures. Even if local anesthetic is placed directly in the lower hock joint, it’s possible the origin of the suspensory ligament will be impacted. That said, blocks may still be necessary to help pin down a diagnosis.

Radiographs can be helpful in this situation—and are a crucial part of making an accurate diagnosis in this case. Hock arthritis is typically diagnosable on radiographs. If the suspensory

The Question:

Diagnostic Dilemmas:

ligament is injured at the point of attachment to the bone, a radiographic view that’s focused on this point of attachment just below the hock can show reactive bone in that location. If a suspensory ligament problem is suspected, the next step will be an ultrasound examination that may provide a definitive answer. However, there are instances of suspensory injury where the ultrasound will be normal. If your vet is still suspicious of a suspensory problem even with a normal ultrasound exam, she may recommend further diagnostic steps.

Acoustic myography is a technique that measures pressure waves in tissues, and has been shown to provide information about whether the suspensory ligament is functioning normally. This diagnostic tool can provide information to help diagnose suspensory ligament injuries that may not be detectable with an ultrasound. Nuclear scintigraphy (bone scan) is another potential diagnostic step that could be taken to identify a suspensory ligament injury at the attachment to the bone. For a bone scan, your horse will be administered a radiographic substance intravenously that’ll accumulate in areas of increased blood flow. If the bone is inflamed, a hot spot will be detected. Finally, an MRI can be used to obtain a detailed picture of both bone and soft tissue structures. This is likely to be a last step in a complicated case. Unlike for feet where an MRI can be performed with your horse standing and sedated, an MRI of the hock/high suspensory area will typically require general anesthesia in order to control movement.

Treatment recommendations for simple hock arthritis is completely different from what would be recommended if the suspensory

Why it Matters: