Points of a horse.1
The Parts Book
If you are ordering new parts for your horse, or just want to talk about them, here is a quick anatomy lesson. The terms in the two illustrations in this section may be hard to remember, but they may better than calling everything a whatchamacallit.
Under the hood. The horse’s skeleton.2
A race track can feed laterality. A Swedish study3 of trotters found that of 500 horses, most had symmetrical hindquarters, but in 39 of them, the hindquarters were asymmetrical. The asymmetric horses had significantly lower total earnings, a lower number of races per horse and less impressive racing records (min/km) than the remaining 461 horses. Trainers reported that the asymmetric horses often had difficulties in performing at speed. Of these 39 horses, 30 had a higher tuber sacrale — the top of the hip bone, sometimes called a “hunter’s bump”. The authors noted that the race tracks in Sweden all require that a horse run counterclockwise, and that this would put a greater load on the right side of their bodies.
Writes Marjorie Miller: “a hunter’s bump is evidence of a prior injury to the sacroiliac joint… Sacroiliac subluxation can be caused acutely by a fall, slip, or twisting over a jump, or the injury can be sustained chronically through repetition of a motion or action.4” As our Swedish researchers write, “Hindquarter asymmetries may be a functional adaptation to habitual motion asymmetries — “leggedness” — seen in many horses5 or to unsymmetrical load distribution caused by monotonous work, e.g., one direction only or due to external factors such as underbanked racetrack curves.6”
Most breaks at the track may begin with stress fractures that when masked by pain killers, don’t affect gait. Analyses7 of breaks during races provides some hints that this may be true: horses that were: (a) making good progress through the race, (b) reluctant to start and (c) received “encouragement” in the final 10 s before the time of fracture, were more likely to sustain a fracture. Other clues come from a look at the strains caused by changing the lead leg and turning:
- The lead forelimb is more likely injured than any other.8
- Injuries were more likely to occur during a change of lead leg9
- More injuries are likely to occur on turns than on straight parts of the course.10
My horse broke his right rear ankle at the track before I met him. Could this have been the result of something that started as a stress fracture? I know he went left plenty and must have counted on his right side for power because when I first tried lunging him, he rocketed off counter clockwise in the round pen, but he had no idea what I was talking about when I asked him to go clockwise.
The lopsided rider likely leads to a lopsided horse. For example, about 90% of people have one leg shorter than the other, and up to 75% of people have a right leg that is shorter than the left.11 One study of a number of women riders in walk, trot, left canter, and right canter found that all tipped slightly to the left and moved their right shoulders more in all but the right canter.12
To develop a symmetrical race horse, and to keep them undamaged longer, race tracks should alternate the direction of travel — perhaps clockwise in even-numbered months. I suspect that training a horse to run both clockwise and counterclockwise would help with developing balance and equal strength on both sides. And, as mom said, sit up straight.
1 Image source: “Equine anatomy” https://en.wikipedia.org/wiki/Equine_anatomy. Image at https://en.wikipedia.org/wiki/Equine_anatomy#/media/File:Points_of_a_horse.jpg with caption “English Trakehner gelding, Sybari in standing pose, marked with major points of the horse. Foaled in 2001, picture taken in 2010 (aged 9). Annotated with major morphological points sourced from Goody, John (2000) Horse Anatomy (2nd ed.), J A Allen ISBN: 0.85131.769.3. and (2007) Complete Equine Veterinary Manual, David & Charles ISBN: 0.7153.1883.7.”
2 Image source: “Skeletal system of the horse”. Wikipedia. https://upload.wikimedia.org/wikipedia/commons/3/33/Horseanatomy.jpg
3 Dalin, G., Magnusson, L.E., Thafvelin, B.C., 1985. Retrospective study of hindquarter asymmetry in Standardbred trotters and its correlation with performance. Equine Vet. J. 17, 292–296.
4 King, Marcia “Hunter’s Bump” The Horse. Oct 1, 2003. http://www.thehorse.com/articles/14145/hunters-bump
5 Björck, Gustaf. Studies on the draught force of horses: development of a method using strain gauges for measuring forces between hoof and ground. Scandinavian Association of Agricultural Scientists and the Royal Swedish Academy of Agriculture and Forestry, 1958.; Drevemo, S., Dalin, G., Fredricson, I. and Hjertkn, G. (1980) Equine locomotion : 1. The analysis of linear and temporal stride characteristics of trotting Standardbreds. Equine vef. J. 12.60-65. ; Drevemo, S., I. Fredricson, G. Dalin, and K. Björne. “Equine locomotion: 2. The analysis of coordination between limbs of trotting Standardbreds.” Equine veterinary journal 12, no. 2 (1980): 66-70.
6 Dalin, G., Drevemo, S., Fredricson, I., Jonsson, K. and Nilsson, G. (1973) Ergonomic aspects of locomotor asymmetry in Standardbred horses trotting through turns. Acta. vet. scand. Suppl. 44, 111-139.
7 Parkin, T. D. H., P. D. Clegg, N. P. French, C. J. Proudman, C. M. Riggs, E. R. Singer, P. M. Webbon, and K. L. Morgan. “Analysis of horse race videos to identify intra-race risk factors for fatal distal limb fracture.” Preventive veterinary medicine 74, no. 1 (2006): 44-55.
8 Ueda, Y., Yoshida, K., Oikawa, M., 1993. Analyses of race accident conditions through use of patrol video. J.
Equine Vet. Sci. 13, 707–710.
9 Cohen, N.D., Peloso, J.G., Mundy, G.D., Fisher, M., Holland, R.E., Little, T.V., Misheff, M.M., Watkins, J.P.,
Honnas, C.M., Moyer, W., 1997. Racing-related factors and results of prerace physical inspection and their
association with musculoskeletal injuries incurred in Thoroughbreds during races. J. Am. Vet. Med. Assoc.
211, 454–463.; Parkin, T. D. H., P. D. Clegg, N. P. French, C. J. Proudman, C. M. Riggs, E. R. Singer, P. M. Webbon, and K. L. Morgan. “Analysis of horse race videos to identify intra-race risk factors for fatal distal limb fracture.” Preventive veterinary medicine 74, no. 1 (2006): 44-55.
10 Ueda, Y., Yoshida, K., Oikawa, M., 1993. Analyses of race accident conditions through use of patrol video. J.
11 Knutson, Gary A. “Anatomic and functional leg-length inequality: a review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance.” Chiropractic & osteopathy 13, no. 1 (2005): 11.; Knutson, Gary A. “Anatomic and functional leg-length inequality: A review and recommendation for clinical decision-making. Part II, the functional or unloaded leg-length asymmetry.” Chiropractic & osteopathy 13, no. 1 (2005): 12.
12 Symes, Debbie, and Robert Ellis. “A preliminary study into rider asymmetry within equitation.” The Veterinary Journal 181, no. 1 (2009): 34-37.