Equine gait analysis tools allow us to get precise measurements of movement asymmetries in horses. Unlike in the past, there is no longer a need to travel specialist research centres. We are, in fact, getting to the exciting point when equine gait analysis is becoming more accessible and affordable for the wider equestrian community thanks to the recent advances in wearable technologies such as small wireless sensors as well as marker-less tracking of movement from videos.

Why is equine gait useful?

Traditionally, evaluation of horse’s movement relied on visual examination. However, there are some significant limitations to this assessment. Firstly, research shows that we are simply not capable of noticing small deviations from symmetry – previous research suggests that asymmetries below 25% are hard to spot (1). Secondly, studies have shown that the same evaluator does not achieve 100% agreement with their own previous evaluation of the same horse, i.e. when they were presented with the same video recording twice at different time points. And that the agreement between multiple evaluators is even worse – in fact it can be as low as 40% depending on the type (forelimb/hindlimb) and severity of lameness.

In contrast, equine gait analysis tools can detect very small asymmetries with high sensitivity and has high repeatability between trials (2). Measuring movement patterns objectively is important because it allows us to quantify what is happening and it also helps us decide what works and what does not (such as training or rehabilitation methods). As a consequence, objective evaluation of the movement asymmetries in horses has greatly enhanced our knowledge about how horses move and what movement adaptations can be observed in response to pain.

The basics of equine gait analysis

When evaluating horses, we often look at movement symmetry (or asymmetry). This is most frequently done in trot as trot is a symmetrical gait so it is easy to compare left and right ‘half’ of the stride. Additionally, in trot the forces acting on the horses limbs are higher than in walk hence magnifying any irregularities which might be related to pain. Limb parameters can be evaluated (for example protraction or retraction) but these have been shown to be highly variable so a lot of the recent research has concentrated on the evaluation of upper body movement asymmetries instead. 

Movement asymmetry parameters

The two most frequently evaluated movement asymmetry parameters are related to  the vertical displacement (i.e. the up and down movement) of the head (measured at the poll), withers and pelvis (measured at sacrum and/or tuber coxea) :

The difference in minimum positions:

• For head we are looking if the head nods down equally during impact of left and right forelimb and similarly for pelvis we look whether the pelvis reaches the same lowest point during the stance of the right and left hindlimb. Horses tend to hold their head higher during the stance of the lame forelimb  (which appears like a head nod on the sound forelimb) and similarly the pelvis drops less during the stance of the lame hindlimb.
  • Note: In research papers these will be labelled as HDmin (Head Difference in Minima) for head and PDmin for pelvis – this will be an average from a number of strides

The difference in maximum positions:

• Here we look at how high the head or pelvis rises after the stance go left and right limb. The head tends to rise less after the dance of the lame forelimb and the pelvis rises less after the stance of the lame hindlimb
  • Note: In research papers these will be labelled as HDmax for head and PDmax for pelvis

A hip hike difference:

• This is the difference between the upward movement amplitude of left and right tuber coxae (hip bones) during contralateral hindlimb stance. For hindlimb lame horses there will be greater amplitude on the side of the lame limb.
  • Note: In research papers this will be labelled as HHD.

An example of HDmin and HDmin parameters for a horse with left fore lameness pattern. The light blue lines indicate vertical displacement of the head during one trot stride, the dark blue line is an average over all strides.

The degree of asymmetry, as measured by the parameters above, has been show to increase with lameness grades (3-4). Correspondingly, horses show reduced upper body movement asymmetries after successful nerve or joint block, i.e. when the pain is reduced or abolished (5-7). Therefore these movement asymmetry parameters are useful for screening and monitoring purposes. 

Where can you learn more about equine gait analysis?

If you want to learn more about equine gait analysis and movement asymmetries in horse, check out the 10 handy resources below.

Podcasts

1) Objective gait assessment and movement asymmetry – Dr Gillian Tabor (Stable Science by Dr David Marlin)

2) Lameness Diagnostics Using a Smartphone and Other Motion Capture Insights with Dr. Aagje Hardeman (Sports Horse Podcast)

3) Developments in gait analysis that help identify pain related asymmetry could support your training and coaching, with Eva Marunova (River Tiger Podcast)

Webinars

4) Biomechanics behind gait analysis with Sleip with Elin Hernlund, DVM, PhD, Diplomate ECVSMR 

5) Does conformation affect gait with Prof Renate Weller 

6) Applied Equine Locomotor Biomechanics: Insights from Assessing Upper Body Movement by Dr.-Ing  Thilo Pfau

7) Asymmetrical or Lame? Where do we draw the line? with Dr Eva Marunova

Open access review paper on equine movement analysis

8) Research trends in equine movement analysis, future opportunities and potential barriers in the digital age: A scoping review from 1978 to 2018 (Egan et al., 2019)

Training videos for recognition of lameness patterns:

9) Lameness Trainer

10) Lameness Lab (University of Guelph)

You might also enjoy reading my equine biomechanics blog series:

• Biomechanics of walk
• Biomechanics of trot
• Biomechanics of canter

References:

1 Parkes et al. (2009) Evidence of the development of ‘domain-restricted’ expertise in the recognition of asymmetric motion characteristics of hindlimb lameness in the horse. Equine Veterinary Journal https://doi.org/10.2746/042516408X343000

2 Keegan et al. (2011) Assessment of repeatability of a wireless, inertial sensor-based lameness evaluation system for horses. American Journal of Veterinary Research https://doi.org/10.2460/ajvr.72.9.1156

3 Keegan et al. (2013) Comparison of a body-mounted inertial sensor system–based method with subjective evaluation for detection of lameness in horses. American Journal of Veterinary Research. https://doi.org/10.2460/ajvr.74.1.17

4 Müller-Quirin et al. (2020) Riding Soundness—Comparison of Subjective With Objective Lameness Assessments of Owner-Sound Horses at Trot on a Treadmill. Journal of Equine Veterinary Science. https://doi.org/10.1016/j.jevs.2020.103314

5 Maliye et al. (2013) An inertial sensor-based system can objectively assess diagnostic anaesthesia of the equine foot. Equine Veterinary Journal https://doi.org/10.1111/evj.12158
6 Keegan et al. (1997) Effects of anesthesia of the palmar digital nerves on kinematic gait analysis in horses with and without navicular disease. American Journal of Veterinary Research
7 Pfau et al. (2014) Identifying optimal parameters for quantification of changes in pelvic movement symmetry as a response to diagnostic analgesia in the hindlimbs of horses. Equine Veterinary Journal https://doi.org/10.1111/evj.12220