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Present data describe the rates of vertical loading and unloading generated by clinically normal dogs in a trotting gait. Forward velocity was found to influence maximal rates of limb loading and unloading in forelimbs and hind limbs. The rates increased as the velocity of the dog/handler increased. The position of maximal limb loading during the stance phase was independent of velocity in the forelimbs, but in the hind limbs, as velocity increased, the position of maximal unloading occurred earlier in the stance phase.

Within velocity groups, the forelimbs had greater rates of vertical loading and unloading than did hind limbs. The position at which maximal loading occurred was earlier in the forelimbs than in the hind limbs. There was a difference in the position of maximal unloading between forelimbs and hind limbs, with the forelimbs unloading earlier in the stance phase. Difference between paired forelimbs or paired hind limbs was not found for any measurement within any group.

Calculation of loading and unloading rates provides another method of examining functional limb loading in dogs. This method of analysis can be adapted to any animal gaited across a force platform in which single limb strides can be recorded. Calculations can also be done in any axis of measurement. Data indicated loading and unloading rates to be consistent, and easily determined. Use of data generated from rates of limb loading can be classified into 2 areas: documentation of acceptance of load by the limb, and indirect measurement of functional stresses placed on bones of the appendicular skeleton.

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in American Journal of Veterinary Research



To evaluate clinical and biomechanical gait variables in a group of dogs before and after (for 1 year) total hip replacement.


16 dogs with degenerative joint disease of the coxofemoral joint secondary to hip dysplasia deemed candidates for total hip replacement.


Before and at 1, 3, 6, and 12 months after surgery, each dog was trotted over a biomechanical force platform. Vertical force data evaluated for each stance phase of the treated and untreated hind limbs included peak force, impulse, and limb loading and unloading rates. Vertical peak and impulse data were also evaluated for the forelimbs. Measurements analyzed in the craniocaudal axis, divided into braking and propulsion phases, consisted of peak force and associated impulses. Also, orthopedic examination for each dog included subjective scoring for limb lameness at each evaluation period.


Most ground reaction forces (GRF) were significantly lower before surgery for the proposed treated, compared with the proposed untreated, limb. This difference between limbs continued through postoperative month 1. Also at 1 month, some treated limb values were significantly lower than preoperative values. By 3 to 6 months, treated limb GRF increased so that no significant difference between limbs could be found. Vertical and craniocaudal propulsion impulse values were significantly higher in the treated than untreated limb from the 6-month evaluation period through the remainder of the study. Braking component of the craniocaudal axes measurements was unchanged throughout the study.


GRF indicated that dogs of this study had significantly increased loading function of the treated hind limb by 6 months after unilateral total hip replacement. Data also indicated that some force was transferred from the untreated to treated hip over the study period. Loading rates also increased over the study period, indicating increased willingness to load the treated hip over time. Craniocaudal axis data ndicated no improvement in braking forces with coxofemoral joint replacement, suggesting that the coxofemoral joint with degenerative joint disease did not have altered braking performance at a trotting gait. Comparison of subjective lameness scores and objective GRF indicated that visual grading of coxofemoral joint lameness is limited. (Am J Vet Res 1996;57:1781–1785)

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in American Journal of Veterinary Research


Limb symmetry was evaluated by measuring ground reaction forces in 2 groups of normal-gaited dogs at a trot. Data were collected from 2 groups of 21 dogs trotted at dog/handler velocities of 1.25 to 1.55 m/s and 1.85 to 2.05 m/s, respectively. Of these dogs, 9 participated in both groups to allow comparison of data at both velocities. Additionally, 16 of the dogs in group 1 were measured in 2 directions of movement to determine whether directional dependence was present. Collected data were then applied to 3 described symmetry indices.

Each index was easy to calculate, but all had limitations. A major limitation was variation in magnitude of ground reaction forces measured between the different axes and the effect of this variation on precision of the derived indices. Vertical ground forces provided the most consistent symmetry indices, in part because of their large magnitude. The indices indicated that no dog had perfect right-to-left symmetry during a trotting gait. Statistical differences were not found in any of the measurements of directional dependence. Likewise, comparing symmetry data in dogs trotted at both velocities indicated no significant differences in any axis.

However, further analysis of the data revealed the actual amount that a variance attributable to right-left limb variation was negligible. Most of the variance was attributable to trial variation. Thus, the aforementioned indices, which use nonconsecutive footfall methods to evaluate limb symmetry, actually measure principally trial variation and not limb-to-limb variation.

Free access
in American Journal of Veterinary Research