Treadmill exercise testing. Treadmill installation and training protocols used for clinical evaluations of equine athletes

The use of motorized treadmills has made it possible to evaluate equine poor performance with sophisticated diagnostic techniques during peak exercise. Treadmill exercise tests currently being used for clinical evaluations include treadmill gait analysis, dynamic hoof balancing, endoscopic evaluation of upper airway function, and exercise performance profiling. Large motorized treadmills (1 to 1.5 m in width and 4 to 5 m in length) are best suited for clinical evaluations. Ideally, the treadmill should be installed in-ground using a pit. This type of installation results in the tread surface being at the same level as the surrounding floor. A standard protocol should always be used to train horses to exercise on a treadmill. Training should be designed to introduce the horse to procedures required for a specific clinical evaluation gradually.     

Repeatability of subjective evaluation of lameness in horses

Reasons for performing study: Previous studies have suggested that agreement between equine veterinarians subjectively evaluating lameness in horses is low. These studies were limited to small numbers of horses, evaluating movement on the treadmill or to evaluating previously‐recorded videotape. Objectives: To estimate agreement between equine practitioners performing lameness evaluations in horses in the live, over ground setting. Methods: 131 mature horses were evaluated for lameness by 2–5 clinicians (mean 3.2) with a weighted‐average of 18.7 years of experience. Clinicians graded each limb using the AAEP lameness scale by first watching the horse trot in a straight line only and then after full lameness evaluation. Agreement was estimated by calculation of Fleiss' (κ). Evaluators agreed if they picked the same limb as lame or not lame regardless of the severity of perceived lameness. Results: After only evaluating the horse trot in a straight line clinicians agreed whether a limb was lame or not 76.6% of the time (κ= 0.44). After full lameness evaluation clinicians agreed whether a limb was lame or not 72.9% of the time (κ= 0.45). Agreement on forelimb lameness was slightly higher than on hindlimb lameness. When the mean AAEP lameness score was >1.5 clinicians agreed whether or not a limb was lame 93.1% of the time (κ= 0.86), but when the mean score was ≤1.5 they agreed 61.9% (κ= 0.23) of the time. When given the task of picking whether or not the horse was lame and picking the worst limb after full lameness evaluation, clinicians agreed 51.6% (κ= 0.37) of the time. Conclusions: For horses with mild lameness subjective evaluation of lameness is not very reliable. Potential relevance: A search for and the development of more objective and reliable methods of lameness evaluation is justified and should be encouraged and supported.     

The effect of induced hindlimb lameness on thoracolumbar kinematics during treadmill locomotion

REASON FOR PERFORMING STUDY: There are no detailed studies describing a relationship between hindlimb lameness and altered motion of the back. OBJECTIVES: To quantify the effect of induced subtle hindlimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses were measured during walk and trot on a treadmill before and during application of pressure on the sole of the left hindlimb using a well-established sole pressure model. Reflective markers were located at anatomical landmarks on the limbs, back, head and neck for kinematic recordings. Ground reaction forces (GRF) in individual limbs were calculated from kinematics to detect changes in loading of the limbs. RESULTS: When pressure on the sole of the hindlimb was present, horses were judged as lame (grade 2 on the AAEP scale 1-5) by an experienced clinician. No significant unloading of this limb was found in the group of horses (unloading was observed in 4 animals, but was not detectable in the other 2), but statistically significant effects on back kinematics were detected. The overall flexion-extension (FE) range of motion (ROM) of the vertebral column was increased at walk, especially in the thoracic segments. Axial rotation (AR) ROM of the pelvis was also increased. At trot, the FE ROM was decreased only in the segment L3-L5-S3. During the stance phase of the lame limb, the segment T6-T10-T13 was more flexed and the neck was lowered at both gaits; the thoracolumbar segments were more extended at walk and trot. There were no significant changes in the stride length or protraction-retraction angles in any of the limbs. CONCLUSIONS: Subtle hindlimb lameness provoked slight but detectable changes in thoracolumbar kinematics. The subtle lameness induced in this study resulted in hyperextension and increased ROM of the thoracolumbar back, but also in decreased ROM of the lumbosacral segment and rotational motion changes of the pelvis. POTENTIAL RELEVANCE: Even subtle lameness can result in changes in back kinematics, which emphasises the intricate link between limb function and thoracolumbar motion. It may be surmised that, when chronically present, subtle lameness induces back dysfunction.     

The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion

REASONS FOR PERFORMING STUDY: Lameness has often been suggested to result in altered movement of the back, but there are no detailed studies describing such a relationship in quantitative terms. OBJECTIVES: To quantify the effect of induced subtle forelimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses was measured at walk and at trot on a treadmill before and after the induction of reversible forelimb lameness grade 2 (AAEP scale 1-5). Ground reaction forces (GRF) for individual limbs were calculated from kinematics. RESULTS: The horses significantly unloaded the painful limb by 11.5% at trot, while unloading at walk was not significant. The overall flexion-extension range of back motion decreased on average by 0.2 degrees at walk and increased by 3.3 degrees at trot (P<0.05). Changes in angular motion patterns of vertebral joints were noted only at trot, with an increase in flexion of 0.9 degrees at T10 (i.e. angle between T6, T10 and T13) during the stance phase of the sound diagonal and an increase in extension of the thoracolumbar area during stance of the lame diagonal (0.7degrees at T13, 0.8 degres at T17, 0.5 degres at L1, 0.4 degrees at L3 and 0.3 degrees at L5) (P<0.05). Lameness further caused a lateral bending of the cranial thoracic vertebral column towards the lame side (1.3 degrees at T10 and 0.9 degrees at T13) (P<0.05) during stance of the lame diagonal. CONCLUSIONS: Both range of motion and vertebral angular motion patterns are affected by subtle forelimb lameness. At walk, the effect is minimal, at trot the horses increased the vertebral range of motion and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes, presumably in an attempt to move the centre of gravity away from the lame side and reduce the force on the affected limb. POTENTIAL RELEVANCE: Subtle forelimb lameness affects thoracolumbar kinematics. Future studies should aim at elucidating whether the altered movement patterns lead to back and/or neck dysfunction in the case of chronic lameness.     

Vertical Frontlimb Ground Reaction Forces of Sound and Lame Warmbloods Differ From Those in Quarter Horses

Lameness is a highly prevalent condition in horses and is the principal cause of removal from athletic activity in this species. In evidence-based veterinary medicine studies to evaluate non-setoidal anti-inflammatory drug (NSAID) therapies, force plates are commonly used to objectively assess improvement of lameness. The objective of this study was to determine whether breed differences would influence force plate measurements in sound and lame riding horses. Force plate measurements of lame (n = 20) and sound (n = 18) Warmblood and lame (n = 15) and sound (n = 8) Quarter Horses were compared. Lameness was visually scored using the grade 0–5 American Association of Equine Practitioners (AAEP) lameness scale. Trotting sound Warmbloods loaded their frontlimbs with 118% body weight (BW) and their hindlimbs with 96% BW, whereas Quarter Horses only used 101% BW in the front and 92% BW in the hindlimbs (P < .05). Furthermore, it appeared and was estimated that, at trot, front-limb-lame Warmblood horses showed higher peak vertical force (PVF) values (grade 2: 89% BW; grade 3: 69% BW), than front-limb-lame Quarter Horses with similar lameness scores (grade 2: 78% BW; grade 3: 66% BW). In conclusion, peak vertical forces (PVF expressed in % BW) of either lame or sound horses seem to be influenced by breed differences between Warmblood and Quarter Horse riding horses. Possible conformation and gait differences enabled trotting Quarter Horses to demonstrate lower absolute PVF values than Warmbloods, whereas trotting lame Warmbloods showed a relatively larger decrease in frontlimb loading and thus in PVF than lame Quarter Horses at a trot. Thus, in studies in which objective lameness observations are recorded, breed differences should be taken into account when specific grades of lameness of a group of horses are to be objectively compared with another group.     

Osteolytic lesions of the tuber calcanei in two horses

Two adult horses were evaluated for chronic hind limb lameness. Nonseptic calcanean bursitis with associated focal osteolytic lesions at the point of insertion of the gastrocnemius tendon was diagnosed in each horse by physical and lameness examinations, radiography, ultrasonography, and synovial fluid analysis. Both horses underwent arthroscopic exploration and lavage of the affected bursa, and one horse also underwent surgical debridement of the osseous lesion. Both horses remained lame for 13 months after the surgical procedures. To our knowledge, osseous lesions of the calcaneus in horses with nonseptic calcanean bursitis have not been reported. The flexed proximoplantar-to-distoplantar tangential radiographic view of the calcaneus was essential in localizing the lesions, as was the sonogram in one horse. Arthroscopy provided a thorough evaluation of the bursa and associated tendons. On the basis of the outcome of these 2 horses, the prognosis for complete recovery for horses with this condition appears to be unfavorable. Surgical debridement of the osseous lesion was of no benefit and may have been detrimental.     

Use of magnetic resonance imaging to diagnose distal sesamoid bone injury in a horse

CASE DESCRIPTION: A 5-year-old Appaloosa mare was examined for severe left forelimb lameness of 4 months' duration. CLINICAL FINDINGS: Lameness was evident at the walk and trot and was exacerbated when the horse circled to the left. Signs of pain were elicited in response to hoof testers placed over the frog of the left front hoof, and a palmar digital nerve block eliminated the lameness. Radiographs revealed no abnormalities, but magnetic resonance imaging (MRI) revealed increased bone density in the medullary cavity of the distal sesamoid (navicular) bone in the proton density and T2-weighted images and a defect in the fibrocartilage and subchondral bone of the flexor cortex. TREATMENT AND OUTCOME: Because of the absence of improvement after 4 months and the poor prognosis for return to soundness, the mare was euthanatized. An adhesion between the deep digital flexor tendon and the flexor cortex defect on the navicular bone was grossly evident, and histologic evaluation revealed diffuse replacement of marrow trabecular bone with compact lamellar bone. Changes were consistent with blunt traumatic injury to the navicular bone that resulted in bone proliferation in the medullary cavity. CLINICAL RELEVANCE: Use of MRI enabled detection of changes that were not radiographically evident and enabled accurate diagnosis of the cause of lameness. Navicular bone injury may occur without fracture and should be considered as a differential diagnosis in horses with an acute onset of severe unilateral forelimb lameness originating from the heel portion of the foot.     

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios.Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.     

Kinematic characteristics of Andalusian, Arabian and Anglo-Arabian horses: a comparative study

The aim of this study was to compare the kinematic trot characteristics of three different breeds of horse: Andalusian (AN, n = 15), Arabian (AR, n = 7) and Anglo-Arabian (AA, n = 5) using standard computer-assisted videography (25 Hz). Linear, temporal and angular parameters in fore- and hind limbs were analysed in six randomly selected strides per horse. Normalised angle-time diagrams along the complete stride were obtained for all joints angles in each breed and specific kinematic characteristics were detected graphically. AA horses displayed longer swing durations in both limbs ans a shorter angular range of motion (ARM) in scapula and pelvis inclination and in shoulder, hip and forelimb retraction-protraction angles. At lift off, stifle and tarsal joint angles were more flexed. In general, only small differences were observed in AR horse kinematics when compared with the other 2 breeds. AN horses presented negative overtracking length, which was positive in AR and AA. In AN horses the elbow and carpal joints were more flexed at the moment of maximal elevation, elbow and fore-fetlock joints also exhibited a larger ARM due to a smaller angle at maximal flexion. In the hind limbs, tarsal, hind fetlock and retraction-protraction angles presented a larger ARM in AN horses due to greater maximal flexion in the tarsal and hind fetlock joints. Fore- and hind fetlocks were also more flexed in horses from this breed. In conclusion, differences between kinematic variables at the trot were observed in the three breeds studied here, mainly in forelimb joints. The most outstanding feature was the greater forelimb flexion recorded in AN horses than in the other breeds which is consistent with the elevated movements in this breed. In AA horses, the ARM of proximal joints involved in retraction protraction in both fore- and hind limbs was smaller. All the differences observed highlighted the idiosyncratic nature of the trot in each breed; this may influence the functional capacity of each breed.     

Bilateral lameness in horses a kinematic study

Summary

The kinematic pattern of mild bilateral lameness was studied by inducing a supporting limb lameness in both forelimbs of 11 sound Dutch Warmblood horses. The kinematics of the horses were recorded while they trotted (3.5 m/s) on a treadmill. The locomotion analysis system CODA‐3 was used to determine the temporal stride patterns, limb movements as well as head and trunk movement patterns. The transient lameness model, by which pressure‐induced pain is evoked on the hoof sole, was used. Differences between left and right limbs as well as between the sound and the lame condition were tested using a paired t‐test.

Stride and stance duration did not change significantly (p < 0.05) during bilateral lameness compared to the pattern of sound horses. Diagonal advanced placement changed to an earlier placement of both forelimbs. Fetlock hyperextension decreased also in both forelimbs, while the pro‐ and retraction, hoof impact angle, maximal hoof height, and all hind limb variables remained unchanged. Vertical head and trunk movements tended to decrease, but these changes were not significant.

It was concluded that fetlock hyperextension and diagonal advanced placement indicate locomotor disturbances, but that mild bilateral lameness may be difficult to distinguish from individual patterns in single assessments because of the lack of locomotor asymmetries. Evaluation of these variables at regular intervals may allow an early detection of bilateral lameness, which then could be confirmed by diagnostic local anaesthesia.     

Evaluation of discriminant analysis based on dorsoventral symmetry indices to quantify hindlimb lameness during over ground locomotion in the horse

Reasons for performing study: Advances in gait analysis techniques have led to assessment tools that can aid in detecting and quantifying lameness; here, bilateral tuberà coxae and pelvic movement during over ground locomotion are compared in order to investigate a practical method to assess hindlimb lameness in the horse. Objectives: To evaluate which parameters from anatomical landmarks on trunk and proximal hindlimbs are the best indicators of degree and side of hindlimb lameness. Methods: Fifteen horses (age 11–23 years, 6 nonlame and 9 unilaterally hindlimb lame horses 1/10 to 2/10 lame) were fitted with 4 inertial sensors: tuber sacrale, left and right tubera coxae and withers; 889 strides were collected from 6 trot trials per horse. Horses were assessed for lameness by a qualified equine orthopaedic surgeon from videos. Vertical displacement data for each sensor were used to calculate symmetry indices as well as published Fourier analysis based parameters. Linear discriminant analysis was used to determine the most discriminative parameters for 2 scenarios: grading of severity of lameness and identification of the affected limb. Results: Pelvic energy ratio gave the best indication for the degree of lameness. Directional symmetry index of the tubera coxae sensors yielded the highest discriminative power for identification of the lame limb. Conclusions and potential relevance: A good indication of the degree of hindlimb lameness can be obtained from vertical displacement data of the pelvic midline, collected from inertial sensors during over ground locomotion. The trunk mounted inertial sensor system allows for a time efficient collection of a representative database from horses with differing grade and site of lameness in a clinical setting. This is crucial for future work on a robust definition of the best parameters for lameness classification under practical conditions.     

Idiopathic hopping‐like forelimb lameness syndrome in ridden horses: 46 horses (2002–2014)

There has been no analysis of a hopping‐type forelimb lameness syndrome seen in ridden horses. The objectives of this retrospective study were to describe the clinical features of this syndrome, response to diagnostic analgesia and imaging findings and to document post mortem findings. Clinical records from 2002 to 2014 were reviewed and data concerning signalment, history, lame limb(s), lameness characteristics, response to diagnostic analgesia and diagnostic imaging were recorded. There were 46 horses from 4 to 13 years of age, 6 of which had a history of known or suspected trauma immediately before the onset of reduced performance or lameness. Lameness seen when ridden was characterised by an intermittent shortened cranial phase of the step of the lame forelimb at the trot and marked elevation of the head as the affected limb was protracted, with the horse appearing to ‘hop’ (on the contralateral limb) as if trying to break to canter. When lameness was at its worst horses were unwilling to trot. Three horses showed sporadic severe stumbling. Local analgesia of the affected limb did not improve the lameness and in 16 horses lameness deteriorated. Three of 5 horses showed some improvement (≥2/8 grades) in the hopping‐type lameness after intra‐articular analgesia of the articular process joints of the sixth and seventh cervical vertebrae, ipsilateral to the lame forelimb. Radiographic, ultrasonographic and nuclear scintigraphic examinations were inconclusive. Two of 4 horses responded to treatment with gabapentin. In 3 horses post mortem examination revealed mild lymphocytic inflammation within or around the dorsal root ganglia of the fifth and sixth cervical nerve roots, sixth cervical nerve root or second thoracic nerve root ipsilateral to the lame limb. Idiopathic hopping‐type lameness syndrome in ridden horses may be a pain‐related condition ± a neurological component and currently has a guarded prognosis.     

Effect of induced unilateral synovitis of distal intertarsal and tarsometatarsal joints on sagittal plane kinematics and kinetics of trotting horses

OBJECTIVE: To study the effect of unilateral synovitis in the distal intertarsal and tarsometatarsal joints on locomotion, including the compensating effects within and between limbs. ANIMALS: 4 clinically normal horses. PROCEDURE: Gait analyses including kinematics, force plate, and inverse dynamic analysis were performed at the trot before lameness, after which synovitis was induced by injecting endotoxin into the right distal intertarsal and tarsometatarsal joints. Gait analyses were repeated 24 to 30 hours later during lameness. Differences between the stride variables during the 2 conditions (lame and sound) were identified. RESULTS: Tarsal joint range of motion, peak vertical force, and vertical impulse were decreased during lameness. Mechanical deficits included a decrease in negative work performed by the tarsal extensors during the early stance phase and a decrease in positive work by the tarsal extensors during push off. No compensatory changes in work were performed by other joints within the lame hind limb during the stance phase. Vertical impulse in the diagonal forelimb decreased, but there were no significant changes in forces or impulses in the ipsilateral forelimb or contralateral hind limb. CONCLUSION AND CLINICAL RELEVANCE: Results indicate that horses are able to manage mild, unilateral hind limb lameness by reducing the airborne phase of the stride rather than by increased loading of the compensating limbs.     

Lameness and heart rate elevation in the exercising horse

Seven, healthy, conditioned, Quarter Horse mares with previous treadmill experience were each fitted with an adjustable heart bar shoe on the left front foot and a counterbalanced bar shoe on the right front foot. Three treatments were studied: sound, slightly lame, and obviously lame at a trot. Each subject performed one standardized exercise test (SET) daily on three consecutive days. Each subject underwent one treatment during a SET. Treatment order was randomly assigned. The SET consisted of a 5-rain exercise period at 3.2 m/sec on a treadmill at an 11% grade. Heart rate (HR) was determined at rest, 20 rain after the induction of lameness before the SET, during the last 30 sec of the SET, and at 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, and 60 min postexercise. The Student's paired t test was used to compare HR means for the three treatments at each monitoring interval. Heart rate was higher in slightly lame trials compared to sound trials as rest and at 0.5 through 10 and 30 through 60 min postexercise (P<0.05 to P<0.001). Lame trials evidenced higher HRs than slightly lame trials at rest and at 0.5, 2, 4, and 5 rain of recovery (P<0.05). When lame HRs were compared to sound HRs, differences were noted at rest and at 0.5 through 60 min postexercise (P<0.01 to P<0.001). The heart bar shoe as designed for the treatment of laminitis was effective as a noninvasive, nonpermanent model of lameness pain in normal horses. Increases in HR at rest and during recovery from exercise were observed with experimentally induced lameness. The degree of HR increase seen with lameness was a function of the degree of lameness induced.     

Kinematics of the hind limb in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and intra-articular administration of anesthetic

OBJECTIVE: To identify hind limb and pelvic kinematic variables that change in trotting horses after induced lameness of the distal intertarsal and tarsometatarsal joints and after subsequent intra-articular administration of anesthetic. ANIMALS: 8 clinically normal adult horses. PROCEDURE: Kinematic measurements were made before and after transient endotoxin-induced lameness of the distal intertarsal and tarsometatarsal joints and after intra-articular administration of anesthetic. Fourteen displacement and joint angle (metatarsophalangeal [fetlock] and tarsal joints) measurements were made on the right hind limb, sacrum, and the right and left tubera coxae. Kinematic measurements were compared by general linear models, using a repeated measures ANOVA. Post hoc multiple comparisons between treatments were evaluated with a Fisher least squared difference test at alpha = 0.05. RESULTS: After lameness induction, fetlock and tarsal joint extension during stance decreased, fetlock joint flexion and hoof height during swing increased, limb protraction decreased, and vertical excursion of the tubera coxae became more asymmetric. After intra-articular administration of anesthetic, limb protraction returned to the degree seen before lameness, and vertical excursion of the tubera coxae became more symmetric. CONCLUSIONS AND CLINICAL RELEVANCE: Increased length of hind limb protraction and symmetry of tubera coxae vertical excursion are sensitive indicators of improvement in tarsal joint lameness. When evaluating changes in tarsal joint lameness, evaluating the horse from the side (to assess limb protraction) is as important as evaluating from the rear (to assess pelvic symmetry).     

Force plate gait analysis at the walk and trot in dogs with low-grade hindlimb lameness.

OBJECTIVE: To evaluate the accuracy of force plate gait analysis at the walk and trot in dogs with low-grade hindlimb lameness. MATERIAL AND METHODS: Nineteen healthy dogs and 41 dogs with low-grade unilateral hindlimb lameness due to stifle or hip joint problems were walked and trotted over a force plate. Peak vertical forces (PVF) were recorded, and a symmetry index (SI) was calculated from the PVF of the hindlimbs. 'Cut-off' values were determined from the SI of the normal dogs. These cut-off values were used to discriminate lame dogs from normal ones. Sensitivity and specificity were evaluated for measurements at walk and trot, and the Cohen's Kappa coefficient (k) was used to determine the agreement between clinical lameness and force plate measurements, and between force plate results at walk and trot. Receiver Operating Characteristics (ROC) curve were plotted for both gaits to evaluate accuracy. RESULTS: The sensitivity of the measurements at walk was 0.63, and specifity was 0.95. The sensitivity of the measurements at trot was 0.90, and specificity was 1.0. Moderate agreement was found between force plate measurements at walk and trot, and between clinical gait assessment and force plate measurements at walk. Good agreement was found between clinical gait assessment and measurements at trot. ROC analyses revealed the trot (94.7% [91.7%; 97.7%]) to be the more accurate test than the walk (85.0% [80.1%; 89.9%]). CONCLUSION: The trotting gait was more sensitive and accurate than the walking gait for the differentiation of dogs with a low-grade hindlimb lameness from normal ones using force plate gait analysis.     

Subjective Gait Assessment of 57 Sports Horses in Normal Work: A Comparison of the Response to Flexion Tests,Movement in Hand,on the Lunge,and Ridden

Historically, lameness has been evaluated in hand or on the lunge, but some lamenesses may only be apparent ridden. The objectives were to compare the response to flexion tests, movement in hand, on the lunge, and ridden in sports horses in regular work, assumed to be sound by the owners. It was hypothesized that lameness may be apparent in ridden horses that was not detectable in hand or on the lunge. Fifty-seven sports horses in regular work and assumed to be sound were assessed prospectively in hand, on the lunge on both soft and firm surfaces, and ridden. Flexion tests of all four limbs were performed. Lameness was graded (0–8) under each circumstance in which the horse was examined and after each flexion test. Fourteen horses (24.6%) were sound under all circumstances. Six horses were sound in hand, on the lunge, and ridden but showed a grade 1 or 2 lameness after flexion of a single limb. Sixteen horses (26.3%) were lame in hand. Twenty-four horses (42.1%) showed lameness on the lunge on a soft surface, and 23 horses (40.4%) were lame on the lunge on a firm surface. Twenty-seven horses (47.4%) showed lameness ridden; seven (12.3%) were only lame ridden. There was no significant association between age (P = .09) or work discipline (P = .1) and lameness. It was concluded that freedom from lameness in straight lines is not a reliable indicator of soundness. Some lamenesses are only apparent ridden.     

Objective determination of pelvic movement during hind limb lameness by use of a signal decomposition method and pelvic height differences

OBJECTIVE: To evaluate pelvic movement over a large number of strides in sound horses and in horses with induced hind limb lameness by applying methods to the pelvis that have been described for evaluating vertical head movement in horses with induced forelimb lameness. ANIMALS: 17 adult horses. PROCEDURE: Horses were filmed while trotting on a treadmill before and after induction of transient mild and moderate hind limb lamenesses. Vertical pelvic movement was measured by a signal decomposition method. The vertical pelvic signal was decomposed into a periodic component (A1) that occurred at half the stride frequency (representing vertical pelvic movement caused by lameness) and another periodic component (A2) that occurred at stride frequency (representing normal vertical pelvic movement of a trotting horse). Vertical pelvic and foot positions were correlated for each stride to compare the difference between the minimum and maximum heights of the pelvis during and after stance of the right hind limb to the minimum and maximum heights of the pelvis during and after stance of the left hind limb. RESULTS: Maximum pelvic height difference and lameness amplitude (A1) differed significantly between sound and mild or moderate hind limb lameness conditions. Mean A1 value for vertical pelvic movement in sound horses was less than that previously reported for vertical head movement. CONCLUSION AND CLINICAL RELEVANCE: Pelvic height differences and signal decomposition of pelvic movement can be used to objectively evaluate hind limb lameness in horses over a large number of strides in clinical and research settings.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 5. Kinematic effects

AIM: To examine the effect of race training on kinematic parameters of the trot in a sample of 2-year-old Thoroughbred fillies. METHODS: Two-year-old Thoroughbred fillies that had been either trained for racing (n=7) or left untrained in small paddocks (n=7) were examined for lameness, and linear and temporal kinematic data were collected from video recordings of each horse trotted in-hand, 5, 9 and 13 weeks after the beginning of training. Horses were graded as: sound (Grade 0), suspected but not obviously lame (Grade 1), or definitely lame at the trot (Grade 2). RESULTS: Mean velocity at the trot did not vary with lameness grade. Compared with horses classified as sound (Grade 0), horses classified as suspected or definitely lame (Grades 1 and 2) had shorter (2.55 (SE 0.02) vs 2.41 (SE 0.02) and 2.44 (SE 0.03) m; p<0.001) and faster (671 (SE 3) vs 645 (SE 1) and 647 (SE 4) msec; p<0.001) strides. None of the linear or temporal parameters measured varied significantly between the successive observation periods. When data from sound horses were pooled, the training group trotted at a higher mean velocity (4.22 (SE 0.08) vs 3.22 (SE 0.06) m/sec; p<0.001) and with a longer stride length (2.79 (SE 0.05) vs 2.18 (SE 0.06) m; p<0.001) than the untrained group. The stride duration was longer (669 (SE 7) vs 662 (SE 9) msec; p=0.01), stance period was shorter (34.1 (SE 0.6) vs 39.3 (SE 0.7) %; p<0.001) and mid-stance was achieved earlier in the stride (12.1 (SE 0.6) vs 13.1 (SE 0.2) %; p=0.001) in the trained than the untrained group. A longer swing phase in the trained group was associated with an increase in retraction time (9.2 (SE 0.2) vs 7.6 (SE 0.3) %; p=0.001). CONCLUSIONS: These data indicate that early race training in young Thoroughbreds was associated with quantifiable changes in linear and temporal kinematic parameters of the trot, which were related to the race-training objective of improving the horse's ability to work at higher velocities. CLINICAL RELEVANCE: Race training resulted in changes in the gait of non-lame horses at the trot, which should be considered during veterinary lameness examinations.