Diagnosis of Lameness in the Horse

By Liz Devine DVM, MS, DACVS-LA, Pilchuck Veterinary Hospital

An experienced horse owner can tell when a horse’s gait is off, and the resulting loss of use can prove very frustrating. The temptation is to give the horse a day or two off and rush them back to work, but that is not always a good approach.

An Accurate Diagnosis Is Key

When you notice the lameness, it is best to consult with your veterinarian to determine the most effective course of action. An immediate appointment with your veterinarian is not always necessary, but by consulting with them you can decide how long to wait before the horse is seen and what to try at home to help resolve the issue.

Because lameness is often a symptom of an underlying problem, an accurate diagnosis is the single most important factor in the successful treatment of lameness. Working with a veterinarian to determine the root cause of lameness will help get the horse back to work as quickly as possible, with the least risk of recurrence. It’s well worth the time and effort to pursue a professional diagnosis.

Lameness Exam

Planning enough time for the initial lameness exam is critical. To get a correct diagnosis, your veterinarian will do a complete physical exam and will need a precise history from you, including information on:

  • The severity and duration of lameness,
  • Whether it is consistent or waxes and wanes • Any previous treatments and their effects

It’s easy to forget pertinent pieces of information when you are stressed about your horse’s health, so keeping a journal or writing down dates is helpful.

Your veterinarian will start by examining each of the limbs to try and find swollen tendons or joints and figure out what is normal for your horse. Hoof testers are used to squeeze different areas of the foot to see whether there is an abnormal or painful response.

Your veterinarian will also want to watch your horse move as a part of the exam. Horses are typically examined on both hard and soft surfaces, so expect to move between the road or a parking lot and an arena if one is available. They will also want to see the horse move in a straight line and in lunging circles. In some cases, they may want to see the horse move with a rider on its back, so have your tack available at the appointment. Your veterinarian will also perform flexion tests, where the limb is held in a position that stresses certain
 
joints and then the horse is trotted away. Finding the conditions that exacerbate the lameness make it easier to localize the source of the pain.

Nerve/Joint Blocks

In the absence of findings (such as swelling) during the physical exam, it is often necessary to perform serial blocks to figure out what part of the limb is painful. Numbing medications are injected around the nerves or joints to see if the lameness improves when the horse is trotted again. If it does improve, this demonstrates the pain is coming from the numbed area. If the lameness does not improve, the block is repeated on another area. It may be necessary to block different areas on different days in order to find exactly where the pain is coming from. Precise localization of the problem is necessary, so that subsequent diagnostics can identify the cause of the pain and enable effective treatment.

Radiographs (X-rays)

Radiographs are often recommended once the lameness is localized to a specific region of the limb. Radiographs allow vets to look at the bones in the limb, but do not allow for evaluation of soft tissue structures. Combined with the information gained from blocking, radiographs can help diagnose osteoarthritis; bone fragments due to developmental disease or trauma; cysts; fractures; and boney column alignment.

Ultrasound

Ultrasound is used for the evaluation of soft tissue injuries and is also used to look at the surface of the bone. To get a quality image, your veterinarian must clip and properly prepare the target area and have access to a dimly lit, quiet area for the examination. Ultrasound helps vets diagnose moderate to severe injuries in the distal limbs and the stifles but is less effective in very mild or subtle lesions.

Nuclear Scintigraphy (Bone Scan)

In some cases, the entire limb has been blocked and the lameness has not improved. In other cases, the horse does not tolerate a blocking exam, or the lameness is subtle enough that blocking isn’t effective. In these cases, bone scans are very helpful in localizing the lameness; however, further imaging is almost always needed in order to make a definitive diagnosis.

Magnetic Resonance Imaging (MRI)

MRI is very helpful with lameness diagnosis because it evaluates both the bone and soft tissues. MRI is particularly useful when lameness is localized to the foot because it visualizes the structures within the hoof capsule. It is also effective at diagnosing subtle soft tissue injuries in other parts of the limb and detecting damage to the bone before it shows up radiographically.

Multiple Visits Are Common

Simple problems are often diagnosed and treated in one visit, but horse owners should prepare for the possibility that a definitive diagnosis will require multiple visits. Although spending the time to figure out the cause of the lameness can feel like a tedious process, it will greatly increase the chance of successfully treating the issue.