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.
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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.
Scenario #1: My Aching Feet!
The Signs: 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.
The Question: 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.
Diagnostic Dilemmas: The next step in any diagnostic work up of a 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.
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Why it Matters: 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 re-appears after that period of time, you’d be wise to consider taking further steps to pin down a diagnosis before continuing to treat.
Scenario #2: Not Quite Right
The Signs: 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.
The Question: 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 Dilemmas: 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 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.
Why it Matters: Treatment recommendations for simple hock arthritis is completely different from what would be recommended if the suspensory ligament is involved. Most important, a suspensory injury will require a period of rest and rehabilitation to allow for healing. If your horse simply has hock arthritis, he can typically be treated and go right back to work.
It might be tempting to simply treat your horse’s hocks and send him on his way. If he doesn’t improve, you can always take a closer look. This approach is risky. Because the suspensory ligament attaches to the cannon bone just below the hock, injections to treat the hock joints might make your horse’s injured suspensory ligament feel better, too—and if he goes back to work without feeling pain that ligament injury is likely to get worse. Worse yet, if your horse’s hocks get injected regularly as a maintenance procedure with an undiagnosed suspensory injury, the ligament could eventually be damaged beyond repair.
Scenario #3: Catastrophe!
The Signs: You pulled your horse out of his stall, and he was completely non-weight bearing on one leg. You call your vet immediately. Your vet doesn’t feel a throbbing digital pulse that might indicate a sole abscess, and your horse isn’t sensitive to hoof testers. Because an abscess is the most likely cause of a sudden, severe lameness, your vet even pulls the shoe to look for a tract or pus pocket but can’t find anything in the foot. Concerned, she pulls out the x-ray machine, and takes radiographs all the way up your horse’s leg but still finds nothing wrong. She administers pain relieving medications and tells you to leave your horse in his stall. The next day he’s still lame.
The Question: Did your horse just tweak something, or is there a serious injury you haven’t been able to identify, such as a stress fracture?
Diagnostic Dilemma: How could it be a stress fracture if radiographs are normal? Simple. A stress fracture, or crack, in the bone won’t show up immediately. It can take as long as 30 days for the bone along the fracture line to demineralize enough to be visible on radiographs. A bone scan is the ideal tool for identifying a stress fracture or bone injury right after it happens. If a bone scan isn’t in your budget, repeating radiographs 30 days after the injury first occurred might give you an answer.
Why it Matters: Stress fractures heal with an adequate period of rest—typically a minimum of 90 days. If they are stressed before they heal, however, they can blow apart. Your horse seems better after several weeks, and you decide to let him go out in his paddock or pasture. If a stress fracture were present but not identified, a catastrophic fracture could be life-threatening.
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Are you convinced? While it may seem like technology has just made things more complicated, in reality it’s made them better. When your horse comes up lame, it just makes sense to do everything you possibly can to find out why. With an accurate diagnosis in hand, you’ll have the information you need to pursue the most effective treatment available, and keep your horse both safe and sound.