Lameness is one of the most common problems encountered in equine veterinary medicine. The majority of lameness cases are localized to areas within the distal limb; however, the sources, causes, and locations of lameness are diverse. The cause of lameness in horses can be quite complex and often hard to determine. In addition to traditional methods of making a diagnosis, advanced technology is making it easier and more precise for veterinarians to determine the specific cause of lameness in horses.

Lameness may be extremely subtle, affecting only the horse's performance or "felt" by the rider. The more advanced diagnostic techniques are typically reserved for horses in which the more traditional methods of evaluation, such as physical examination, lameness evaluation, and nerve/joint blocks, are unable to locate the site of the lameness. Ancillary diagnostic techniques that may be used include videotaping the gaits of the horse and replaying the video in slow motion, evaluation of the horse across a force plate, use of a kinematic gait analysis system, and diagnostic imaging techniques. By placing small reflective markers on key anatomic locations, 3-dimensional kinematic and kinetic data can be obtained with a camera system to assess locomotion.

Nuclear scintigraphy, thermography, and other diagnostic modalities are sometimes employed to try to determine the location of the lameness. Nuclear scintigraphy, also referred to as bone scanning, can help identify subtle injuries of bone and soft tissue. The procedure involves injecting a labeled radioactive substance into the jugular vein and imaging the uptake of the radioactive material into bone and soft tissue with a gamma camera. Increased uptake is often referred to as a "hot spot." This imaging modality is most useful for acute-onset lamenesses. Nuclear scintigraphy is much more sensitive than radiography for assessing active areas of bony changes, which are most often associated with stress fractures, infection, or other types of bony injury.

In thermography, a visual image is produced from infrared radiation (heat energy) emitted from the skin surface, which may be an indication of inflammation below the surface. The image is typically displayed in colors that correspond to different temperatures.

Once the location of the lameness has been determined, the region may be further evaluated using other diagnostic procedures, including synovial fluid analyses, radiography (X rays), ultrasonography (sonograms), computed tomography (CT or CAT scan), or magnetic resonance imaging (MRI). A synovial fluid sample from a joint or tendon sheath can be useful in certain cases to assess the white blood cell count and protein concentration and other characteristics of the fluid. In cases where joint infection is suspected, synovial fluid can be submitted for bacterial culture and antibiotic susceptibility testing. Radiography is most useful for assessing bony abnormalities including degenerative joint disease (arthritis), osteochondral chip fractures, osteochondrosis, condylar fractures, navicular bone abnormalities, osteomyelitis, and other abnormalities involving bone. Ultrasonography is typically most useful for assessing injuries or abnormalities of the soft tissue such as tendonitis and suspensory ligament desmitis; however, it can also be useful for assessing bone and joints in certain circumstances. Computed tomography provides a three-dimensional assessment of structures and is most useful for assessing bone abnormalities. Currently, CT isn't widely available for horses, and its use is affected by the fact that horses must be placed under general anesthesia and that only the distal limbs can be evaluated. MRI provides a three-dimensional view of structures, especially soft tissues such as tendons, ligaments, bursae, articular cartilage, and joint capsules. Traditionally, MRI has also required horses to be under general anesthesia, which have limited its utility; however, newer equipment, technology, and computer software have enabled MRI to be used in standing, conscious (tranquilized) horses to assess distal limbs.

It should be evident that evaluating lameness in horses involves a comprehensive approach. With today's technologies, the equine veterinarian is better able to diagnose lameness problems. An understanding of the complex nature of lameness in horses and the need for a logical and comprehensive diagnostic approach by an equine veterinarian will reduce frustration and yield satisfaction to horse owners. (For more, see


Rustin M. Moore, DVM, PhD, Dipl. ACVS, is a professor of equine surgery and Director of the Equine Health Studies Program at Louisiana State University's School of Veterinary Medicine. Daniel J. Burba, DVM, Dipl. ACVS, is also a professor of equine surgery at LSU.

About the Author

Rustin M. Moore, DVM, PhD, Dipl. ACVS

Rustin M. Moore, DVM, PhD, Dipl. ACVS, is a professor of equine surgery and Director of the Equine Health Studies Program at Louisiana State University's School of Veterinary Medicine.

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