Improvements in Diagnosing Lameness in Horses

Equine lameness can be defined as any abnormality or asymmetry in a horse's gait. This condition is frequently linked to pain within the horse's limb or elsewhere in the musculoskeletal system. Yet, there can also be instances of mechanical lameness, where the gait is abnormal without necessarily involving pain.

What can cause lameness?

Lameness can manifest in both the front and hind limbs, with a wide range of potential causes. Hoof injuries, such as abscesses or bruised soles from standing on hard objects, can suddenly cause significant lameness. Soft-tissue injuries, like ruptured tendons, and fractured bones can also lead to lameness.

Some cases of lameness develop gradually and worsen over time, often associated with wear and tear on the joints, tendons, or ligaments, known as orthopaedic-type lameness.

Certain equestrian disciplines are more prone to specific types of lameness due to the repetitive nature of the activities. For example, racehorses frequently experience injuries to the superficial digital flexor tendon from high-intensity galloping. Dressage horses may develop proximal suspensory desmitis in the hindlimbs due to the intense collection work required. Stifle lameness is common in showjumpers, who may often strike their stifles on the jumps.

Signs and Symptoms 

Horses exhibiting lameness often display a range of characteristic signs and symptoms. One of the most common indicators of unilateral (one-sided) forelimb lameness is the "head nod." As the lame limb hits the ground, the horse will raise its head and lower it again as the sound limb lands. This behaviour is believed to help the horse take the weight off the affected leg during the weight-bearing phase.

Another sign of lameness is a shortened stride in the lame leg. If both limbs are affected, the horse may exhibit a shuffling gait. Reduced joint flexion in the lame leg may also be observed, and horses with hind limb lameness may drag the toe of the affected leg.

Identifying hind limb lameness can be more challenging than forelimb lameness. In severe cases, a head nod may still be present, with the horse shifting weight forward when the lame hind leg is bearing weight. A more obvious sign is increased up-and-down movement of the point of the hip on the lame side, as the horse tries to minimise weight-bearing on the affected leg.

Some horses may "plait" the lame leg, swinging it outward and then back in, to avoid flexing the joints as much. Bilateral (both-sided) lameness, if mild, can be difficult to detect, and may be characterised by a reduction in performance and changes in behaviour, such as the horse becoming more irritable and reluctant to work. Severe bilateral lameness can be readily apparent, as the horse will be unwilling to move.

Additional behavioural cues associated with lameness include tail swishing, ear-pinning, and a fixed, pained expression in the eyes. Subtle signs of reduced performance should not be overlooked, as some stoic horses may not show overt signs of discomfort. More extreme manifestations of lameness-related pain may include bolting, rearing, and bucking.

Noticing these various signs and symptoms of lameness can help horse owners and caretakers identify and address the issue in a timely manner, ensuring the well-being and optimal performance of their equine companions.

Developments in Lameness Treatments

Equine lameness is a prevalent issue, with numerous horses affected each year. According to the 2015 USDA National Animal Health Monitoring System (NAHMS) study on equine management and select equine health conditions in the United States, 67% of horse operations reported one or more lame horses within the previous year. Approximately 60% of these lame horses underwent a lameness examination performed by a veterinarian.

Mild lameness is typically less concerning for horses with lower levels of athletic activity. Early detection and identification of the cause of low-level lameness can lead to timely treatment, resolution of the issue, and a return to the previous function. Mild lameness is more worrisome in high-performance horses, such as racehorses, three-day event horses, and endurance horses, as it may indicate the onset of a more significant problem. If left untreated, mild lameness can progress to a catastrophic injury, potentially ending the horse's career or even its life. Therefore, effective screening tools are needed to identify early, subtle lameness to prevent minor issues from developing into severe injuries.

The foundation of lameness and musculoskeletal injury diagnosis is a comprehensive lameness evaluation. Notwithstanding, there is poor agreement among veterinarians regarding the affected limb and degree of lameness in horses with mild lameness. Within the past two decades, equine motion analysis devices have been developed and have demonstrated superior accuracy in identifying low-grade lameness compared to visual examination by experienced veterinarians. These systems offer the advantages of ease of use and the ability to be utilised on the farm.

One such system is the Lameness Locator®, which is a user-friendly and precise tool currently employed by veterinarians worldwide. This system comprises three small sensors that can be easily attached to the horse and provide real-time information about the horse's lameness by identifying asymmetric head and pelvic movements. The Lameness Locator® also has the capability to record the type of footing and make comparisons between trials, such as before and after flexion tests and/or blocking.

New Systems for Lameness Analysis

In recent years, the equine industry has witnessed the development of additional motion analysis systems for evaluating horse movement. Two such systems, Pegasus® and EquiMoves®, both originated in Europe. While these newer systems are more recent innovations, they provide similar symmetry indices of the head and pelvis as the established Lameness Locator® system. These advanced systems also incorporate sensors attached to the limbs, enabling the assessment of limb movement. For instance, the Pegasus® system can measure the range of motion in the horse's hocks, as well as the protraction, retraction, abduction, and adduction of all four limbs.

Furthermore, the integration of artificial intelligence has led to even more advancements in equine lameness detection and monitoring. A video-based system called Sleip has been developed, which allows horse owners to upload videos of their horses to a cloud-based platform for professional analysis by veterinarians. This subscription-based program provides an objective means of monitoring horses' conditions without the need for a physical sensor application.

In addition to the improvements in objective lameness assessment, which enables the identification of the specific region of lameness, there have also been recent advancements in diagnostic imaging tools that can aid in localising the source of lameness to specific bony and soft tissue structures. Within the past decade, computed tomography (CT) scanning technology has been adapted for use on standing horses. This type of 3D imaging provides more detailed information about the horse's bony structures compared to traditional radiographs. Furthermore, with the injection of contrast agents, CT scans can also be used to visualise the horse's soft tissue structures. The availability of these standing CT scanners, which offer the same high-resolution imaging capabilities as the previous anaesthesia-based systems, has made this advanced diagnostic tool more accessible for use in equine healthcare.

Treatment and Management

Addressing lameness in horses involves a multifaceted approach, tailored to the specific injury or underlying reason for the horse's impaired mobility. A crucial component of the initial treatment is rest and controlled exercise, with the duration dependent on the nature of the injury.

For ongoing joint problems, such as arthritis, cartilage damage, or ligament injuries, corticosteroid injections often prove to be the most effective and cost-efficient solution. Additionally, innovative therapies like stem cell treatment, platelet-rich plasma (PRP), and polyacrylamide gel can stimulate the healing process in both soft-tissue and joint-related injuries.

In cases where the lameness is attributed to fractures or bone chips, surgical intervention may be necessary to either fix the break or remove the bone fragments.

Proactive management of horses with a history of injury or chronic conditions, such as arthritis, can help prevent further damage and maintain the animal's soundness for an extended period. For horses experiencing wear-and-tear-related issues, introducing variety into their work routine, along with therapeutic exercises like swimming and water treadmill use, can be beneficial.

Alongside the costs of lameness investigation and medication, Petplan Equine insurance may provide coverage for certain alternative therapies that address the conditions mentioned above.

It is crucial to ensure that horses are worked in accordance with their current fitness level and that they are ridden sensibly on a variety of surfaces, avoiding excessive repetitive work. Proper hoof balance and maintaining the correct weight for the individual horse are also important factors in preventing excessive strain on the joints and soft tissues.