Evaluation of lameness under saddle: Effect of the rider (Proceedings)

Evaluation of horse under saddle is performed routinely by some veterinarians and almost not at all by others.  Some of the former strongly feel that a lameness evaluation is not complete without evaluation of the horse under saddle.  The true lameness may be missed.   In opposition, the latter may feel that it is either simply not necessary, a waste of time, or, worse, because of potential the influence of the rider, a distraction, leading the veterinarian on a wild-goose chase, hunting down asymmetric motion thought to be lameness but really only an effect of the rider.  Which is more often correct?

Regretfully, there is only scant objective evidence in support of either opinion, but the early consensus supports the view that the rider can strongly influence the appearance of lameness, both in a positive and negative way.  With this in mind, let us attempt to “keep a score” on the question of whether “a horse should be routinely ridden during lameness evaluations”, which we will designate as answer A, and “a horse should not be routinely ridden during lameness evaluations”, designated answer B.  As preface, let us assume that the lameness evaluation begins with evaluation not under saddle.  Notwithstanding possible unique situations, this is generally true. 

• A good rider can adjust their position and balance skillfully (better than unskilled riders) to be in concert with the movement of the horse.  So, a lameness that is seen without a rider may be covered up under saddle.  If the horse was truly lame, an incorrect assumption could be made that the horse just needs another rider, which would be unfortunate for the horse.  A = 0, B = 1.

• A bad (i.e. unskilled rider) rider increases the variability of the horse's normal movement.  So, consistent asymmetric movement due to lameness will be harder to separate from asymmetric movement due to rider variability.  This is a noise problem.  Separating the true signal quality (lameness) from the noise (rider induced variability) is more difficult.  A = 0, B = 2.

• Specific rider activity, e.g. sit trot, posting, 2- or 3-point stances, will influence the symmetric movement of the horse's head and torso, a sign of possible forelimb and hind limb lameness, respectively.  Asymmetric movement of the rider can then either exacerbate a true lameness (a vote for A), create an apparent but false lameness (a vote for B), or mask (a vote for B) the true asymmetric movement of the horse due to lameness.  A = 1, B = 4.    

• Adding weight increases forces on the limbs and can shift (depending on rider position) majority force to either front or hind limbs.  If it is true, that an increased force on a lame limb will render it more visible, a logical first principle, then a true lameness will be amplified.  This is a vote for A = 2, B = 4.

• Horses under saddle are more exited.  Increased excitement (more adrenaline) covers up small discomforts.  Mild lameness becomes invisible.  This is not fact, just my opinion.  So, no vote is given here.  It is still A = 2, B = 4.

It seems the votes go for B.  It does not support the routine requirement of evaluating the horse for lameness under saddle. 

Most of the studies concerning this question were based on data collections from small numbers of normal horses and/or under rather controlled conditions.  Larger studies specifically measuring effect on natural lameness are lacking.  I am now going to briefly present, in broad strokes to protect intended future publication, an analysis of results of an in-depth study on a large number of horses (sound and with natural forelimb and hind limb lameness), the effects of a rider on the appearance of lameness.  Appearance of lameness was objectively measured with inertial sensors attached to the horse's head and pelvis, and rider activity was objectively measured with inertial sensors attached to the horse.

Horses were evaluated for forelimb and hind limb lameness under the following conditions and activities.  First evaluations, to serve as baselines, were with the horse trotting in a straight line, saddled and bridled but without a rider.  Subsequently, horses were evaluated for lameness under saddle with the rider, riding in circle of two different sized (small and large), first with the rider sitting the trot then posting on the correct limb (on the right forelimb riding to the left and on the left forelimb riding to the right).  Lameness in the forelimb was measured with amplitude of asymmetric vertical head movement taking into consideration both the upward and downward movement.

Results

With the rider sitting the trot the majority of horses showed lameness in the same limb that was indicated when trotting without a rider in a straight line.  Horses in which a different limb was found to be lame during the sit trot had a very mild lameness when evaluated trotting in a straight line without a rider.  Most switching of apparent lameness was to the opposite half of the body and not to the contralateral limb in the same half of the body.  The only movement parameter that was definitely changed during the sit trot was downward movement of the pelvis, which was less during the stance phase of the hind limb towards the inside of the circle in which the horse was being ridden.  This affect was amplified with smaller circles.  This could be interpreted as the potential for the appearance of a false, inner hind limb, impact-type hind limb lameness.  This finding, however, is identical to the potential effect of a horse simply trotting in a circle without a rider. 

When the rider was posting several movement adjustments by the horse could be interpreted as lameness, but the most definitive and predictable was upward movement of the pelvis as the riding was falling into the saddle.  The rider falling into the saddle during posting reduced the upward movement of the pelvis.  Thus, posting on the right forelimb (moving in a left circle) caused the horse to move with an apparent, but false, left hind limb pushoff-type lameness (less left hind limb propulsion), and posting on the left forelimb (moving in a right circle) caused the horse to move with an apparent, but false, right hind limb pushoff-type lameness.  Natural right hind limb lameness during the right forelimb post was masked, and vice versa, natural left hind limb lameness during the right forelimb post was exacerbated.  There was a real and predictable capability of the posting of the rider to falsely affect the appearance of lameness.

The reader is left to make his/her own decision about the utility and necessity of evaluating lame horses under saddle.  Objective evidence indicates that only in cases in which the lameness without a rider is equivocal will evaluation under saddle not distract from the analysis. I do not evaluate horses for lameness under saddle except; 1) when no consistent lameness is visible or measurable with the horse trotting in a straight line, lunging, or after flexion tests, 2) when the history indicates that the lameness is only detectable under saddle, and 3) when the owner insists.

Note:  I do not know what happens to the horse when the rider adopts the 2- or 3-point stance.  My guess is that it is similar to the sit trot, but possibly with less intense effect on the horse.

References

Peham C, Kotschwar AB, Borkènhagen B, et al.  A comparison of forces acting on a horse's back and the stability of the rider's seat in different positions at the trot.  Vet J 2010;184:56-59.

Peham C, Licka T, Schobesberger H, et al.  Influence of the rider on variability of the equine gait.  Human Movement Sci 2004;23:63-671.

Greve L, Dyson S.  The horse-saddle-rider interaction.  Vet J 2013;195:275-281.

Bystrom A, Rhodin M, von Peinen K, et al.  Basic kinematics of the saddle and rider in high-level dressage horses trotting on a treadmill.  Equine Vet J 2009;41:280-284.

de Cocq P, Prinsen H, Springer NC, et al.  The effect of rising and sitting trot on back movements.  Equine Vet J 2009:41:423-427.

deCocq P, Duncker AM, Clayton HM, et al.  Vertical forces on the horse's back in sitting and rising trot. J Biomechanics 2010;43:627-631.

Licka T, Kapaun M, Peham C.  Influence of rider on lameness in trotting horses. Equine Vet J 2004;36:734–736.

Rhodin M, Johnston C, Holm KR, et al.  The influence of head and neck position on kinematics of the back in riding horses at the walk and trot. Equine Vet J 2005;37:7–11.

Rhodin M, Gomez Alvarez CB, Bystrom A, et al.  The effect of different head and neck positions on the caudal back and hindlimb kinematics in the elite dressage horse at trot.  Equine Vet J 2009;41:274–279.

Roepstorff L, Egenvall A, Rhodin M, et al.  Kinetics and kinematics of the horse comparing left and right rising trot.   Equine Vet J  2009;41:292–296.

Symes D, Ellis R.  A preliminary study into rider asymmetry within equitation. Vet J 2009;181:34-37.