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Tendons are a key component of a healthy, functioning musculoskeletal system and yet within the horse’s lower limb they often incur injury, particularly in sport horses.
In racehorses, tendon injuries are a common cause of lameness and decreased athletic performance. Furthermore, injury recurrence is common, even after long recovery periods and consequently tendon injuries are frequently career limiting or career ending.
Decades of research has been conducted to improve veterinary understanding and treatment of tendon injuries. Due to the poor prognosis for tendon recovery, prevention of tendon injuries is better that cure.
Tendons are a specialized form of ﬁbrous connective tissue that are responsible for transmitting forces from muscle to bone to enable movement, but also act as joint stabilisers and as ‘shock absorbers’ to limit muscle damage (Clegg, et al, 2007).
To withstand the mechanical demands, tendon has a unique structure adapting them to their function of resisting tensile forces (Clegg, et al. 2007).
FIGURE 1: IMAGING HAS HELPED IDENTIFY THE STRUCTURE AND FUNCTION OF TENDON
This tendon acts as a spring, absorbing and releasing elastic energy during different phases of the stride, contributing to both the high efﬁciency of locomotion, whilst acting as a shock absorber for the limb (Wilson et al. 2001).
VIDEO 1: A COMPUTER-GENERATED MODEL OF THE EQUINE LIMB. THE SIMULATION PROVIDES FORCES IN THE TENDONS AND LIGAMENTS AND DESCRIBES THE HOOF INTERACTION WITH THE SURFACE. (Source: J.D. Wheat Veterinary Orthopedic Research Lab, 2010).
Tendons undergo high strains to transmit sufficient amounts of energy and work close to their mechanical limits which may help explain the correspondingly high rates of injury (Patterson-Kane et al. 2009).
FIGURE 2: INJURY CAN OCCUR IN ANY PART OF
TENDON BUT BOWED TENDONS ARE COMMON
(Source: Beverly Jacobs Equine, 2015)
A 3 year surveillance study (1996-1998) was conducted by The Jockey Club into racing injuries at British racecourses in flat and NH racing and of 222,993 racing starts, there were 2,358 clinical events reported (1.05% of all starts), and 1,937 of these involved the musculoskeletal system compared to only 421 which involved other body systems. Eighty-one percent of limb injury reports involved forelimbs and 46% involved flexor tendons/suspensory ligaments. (Williams et al. 2001).
Further studies have reported:-
Therefore, tendon damage is a common injury in racehorses and it is the Energy storing tendons that incur the highest injury rates – but how can tendon injuries be prevented?
FIGURE 3: THE SUPERFICIAL DIGITAL FLEXOR TENDON IN THE FORELIMB
OF RACEHORSES IS THE MOST COMMON TENDON TO BE INJURED
(Source: Novobrace, 2015)