Lameness

Lameness is the most frequent abnormality identified in veterinary examinations conducted during harness race meetings in Victoria. Lameness is identified in as many as one in every four veterinary examinations.  The incidence of lameness in Victorian racing standardbreds is comparable to data found in other jurisdictions^. Horses that are lame will often break stride and/or lug to one side.  Lugging usually occurs to the side away from the lameness as the horse attempts to put less force through the sore leg.  Horses can often be sore in more than one leg so identifying the underlying problem can require a comprehensive workup by a treating veterinarian.

Suspensory ligament failure is the most common injury in racing Standardbreds  followed by injuries to the superficial digital flexor tendon (bowed tendon). Disorders of the joints are also common with forelimb problems reported as being slightly more common than hindlimb lameness.  The knee (carpus) is reported to be the most common joint injured during racing although the fetlock, pastern and foot (particularly pedal bone fractures) are also vulnerable.  The hock and the fetlock are common sites for injury in the hindlimb.

Italian veterinary researchers found that standardbred horses receiving medical treatments for subtle lameness or minor gait abnormalities were 2.6 times more likely to sustain a musculoskeletal injury in the 30 days following treatment^. As the second injury did not necessarily occur in the same location as the target for the initial treatment, the researchers concluded that the second (often more serious) injury was pre-existing but had not been identified at the initial work up.   

Even mild lameness will cause a 1 to 2 second decrease  in the mile rate with the most impact occurring in the last quarter mile.  Earlier trainer surveys suggest that only 17% of musculoskeletal problems occur during racing with the bulk of injuries (46%) occurring during training.  Risk factors reported to increase incidence of lameness at any time included performing fast work on tracks with no banking or less banking than commercial racetracks, warm ups of less than nine minutes or longer than ten minutes, training on deep sand and very high training workloads.  Interestingly more recent research suggest that musculoskeletal injuries decrease as the horse races more frequently. This latter observation may simply be a function of sounder horses being able to run more races.  There is evidence, however, that the demands of racing induce adaptive physiological change in the equine athlete that reduce the risk of musculoskeletal injury if the horse is given ample opportunity to recover and adapt after the exertion.

Lameness in standardbred race horses is an important performance and welfare issue.  Although lameness due to musculoskeletal injury is the most common abnormality found during veterinary examinations, trainers need to be aware it is the repetitive overstrain of structures during training rather than racing that makes an injury more likely to occur.  The current research into reducing musculoskeletal injury risk in racing horses is exciting.  Trainers are advised to consult with their veterinarians on different training program approaches. 

Table 1.  Comparison of abnormalities detected during veterinary exams during harness race meetings

In Victoria. * This period marks the employment of Harness Racing Victoria Veterinarians