Dr. Joe Dowd says the device has helped him troubleshoot difficult cases and document the hard-to-see lameness

by Natalie Voss // Feb 20, 2024

When someone first suggested he try a new sensor system called the Lameness Locator on horses at Santa Anita Park, Dr. Joe Dowd says he, like many other veterinarians, was hesitant.

The Lameness Locator, known more formally as the Equinosis Q, is comprised of two sensors placed on a horse’s poll and the point of the hindquarters, together with an accelerometer strapped to the right foreleg. In tandem, the equipment is able to measure changes in stride length, poll height, and hindquarter height, and combine this data to find asymmetries in a horse’s movement. The information gets reported back to software that can show veterinarians which limb is moving abnormally, and whether the issue seems to be on the impact or push-off phase of the stride. While the human eye can capture the equivalent of 15 visual frames per second, the Lameness Locator can gather data on the equivalent of 200 frames per second.

Dowd, who is a partner at the Equine Medical and Surgical Group, said it’s a tall order for many veterinarians to believe the machine can see something better than they can, let alone process that information better than a human.

“Veterinarians are the ones who are slow to adopt it. They’re the sticking point in my environment,” said Dowd, who said trainers, by contrast, are on board with the system after one or two uses. “They don’t feel they need it. I felt the same way, exactly the same way, until somebody I respected introduced me to it.”

And the system does have its limitations – it’s not going to be able to tell you if a muscle group is sore, for example, and it’s calibrated to focus on the limbs and not the back. But in his time working with it, Dowd says the Lameness Locator has become an excellent tool for both diagnosis and communication.

In a presentation at the recent Tex Cauthen Seminar held by the Gluck Equine Research Center, Dowd explained the way he uses the Lameness Locator in his practice.

Sometimes, a trainer or veterinarian can easily tell from watching a horse jog which leg is bothering them and possibly even whether the discomfort is high or low in the limb. Those are the simple cases, because the clinician knows where to begin. A veterinarian like Dowd will apply a lidocaine or mepivacaine injection (colloquially known as a “block”) to a localized part of a limb, which temporarily numbs the structures at and below the block, then has the horse jog again to see if the asymmetry went away. Veterinarians typically start blocks low in the leg move upwards, stopping when the horse looks totally comfortable. At that point, they can feel confident the problem is somewhere between the most recent block and the one before it.

When a horse is lame in multiple limbs, or the lameness is slight and inconsistent, it’s harder to decide where to start. Those are the cases where Dowd will apply the Lameness Locator. The software that accompanies the sensors measures the symmetry between two halves of a trot stride for each leg. It then shows the veterinarian a series of charts that demonstrate how far outside an average range the horse’s symmetry is. The system understands that not every stride will be perfectly symmetrical on even the healthiest of horses, so it uses a vector sum of the whole data set to determine whether the symmetry is in or out of average range. Dowd will use the charts as a guide to begin blocking the horse. If the horse has only one core issue, the next jog with the device will look normal when he’s successfully blocked the right part of the affected leg. In cases where the horse has problems in multiple places, he’ll see the graphs resolve in the area he blocked, but start to shift more severely in a different limb or phase of stride.

All of this quantifies what a veterinarian is already trying to accomplish in a lameness exam. Dowd says he feels confident he or anyone else can say whether a block made 0 difference or 100% difference in a horse’s motion (telling them conclusively that they have found either none of the lameness source or all of it), but when you’re trying to quantify a subtle change in between 70% or 90% improvement for example, it’s easy to be too subjective. It’s easy for an observer to see that a horse has improved compared to the start of an exam, but to miss that there’s still a reduced hitch in the stride. Horses will also adapt to blocks over the course of an exam and may shift their movement in a way that makes them appear to be going better than they are. In the cases Dowd summarized, the Locator’s results tended to quantify what he already suspected, or gave him specificity he was lacking.

Dowd recounted the case of one horse who was presented to him to get approval for a timed workout. The 3-year-old had raced in another jurisdiction and had come to the trainer’s barn after an auction. Dowd didn’t like the way the horse moved, telling the trainer he thought the horse was sore everywhere. Eventually the trainer came to him and said he’d spoken with the previous trainer, who said “he’s always like that. He gallops a mile and he warms up and he’s better.”

“’Listen, that’s hearsay,’” Dowd recalled telling the trainer. “’You don’t know the horse. I don’t know the horse. I can’t pass him.’”

Eventually, the trainer agreed to send the horse to a referral hospital for a bone scan, but there was a scheduling delay. In the meantime, Dowd decided to try the Lameness Locator on the horse. His exam, combined with the Locator’s results, showed discomfort low in all four limbs. Radiographs revealed evidence of Palmar Osteochondral Disease in all four legs, and the total cost to the connections was less than half of what a bone scan would have run to tell them the same thing. The horse got four months of turnout and returned to the races successfully after both Dowd’s observation and the Lameness Locator validated that the asymmetries in his stride were gone.

In that situation, the Locator both assisted in getting to the diagnostic answers the team needed but also provided data illustrating for the trainer what Dowd was seeing. In other cases, it has allowed for early intervention to stop minor problems from becoming more serious.

“It can provide a means of diplomacy,” said Dowd, who encourages other practitioners to give the Locator a try. “The machine doesn’t lie. It’s simply recording data.”