bs_bs_banner
Equine Veterinary Journal ISSN 0425-1644
DOI: 10.1111/evj.12029
An investigation of the relationship between hindlimb lameness and
saddle slip
L. GREVE and S. J. DYSON*
Centre for Equine Studies, Animal Health Trust, Newmarket, Suffolk, UK.
*Correspondence email: [email protected]; Received: 17.08.12; Accepted: 07.12.12
Summary
Reasons for performing study: We have observed saddle slip consistently to one side because of a crooked rider, an ill-fitting saddle, asymmetry in a
horse’s thoracolumbar shape and lameness. Currently, there are no objective data to permit assessment of the relative importance of each factor.
Objectives: To document the frequency of occurrence of saddle slip in horses with hindlimb lameness compared with other horses. To describe the effect of
lameness characteristics and grade, the abolition of lameness by diagnostic analgesia, breed, size, thoracolumbar shape and symmetry and the rider’s
weight.
Methods: One hundred and twenty-eight horses were assessed prospectively, and lameness and saddle slip were assigned a grade before and after
diagnostic analgesia. The thoracolumbar shape and symmetry were measured objectively. In 3 horses, the force distribution and magnitude underneath the
saddle were measured before and after diagnostic analgesia.
Results: The saddle consistently slipped to one side in 38 of 71 horses (54%) with hindlimb lameness, compared with one of 26 horses (4%) with forelimb
lameness, none of 20 (0%) with back pain and/or sacroiliac joint region pain and none of 11 sound horses (0%). The association between saddle slip and
hindlimb lameness was significant (Spearman’s rank correlation coefficient, r = 0.548, P<0.001). Diagnostic analgesia abolishing the hindlimb lameness
eliminated the saddle slip in 37 of 38 horses (97%). In 2 horses, the saddle continued to slip after resolution of lameness; one horse had bilateral forelimb
lameness and the other horse had concurrent hindlimb and forelimb lameness. The saddle of both these horses was asymmetrically flocked. The saddle
slipped to the side of the lamer hindlimb in most horses (32 of 37 [86%]). No horse with saddle slip had significant left–right asymmetry of the back at 4
predetermined sites.
Conclusions and clinical relevance: Hindlimb lameness is an important factor in inducing saddle slip. Saddle slip may be an indicator of the presence of
hindlimb lameness.
Keywords: horse; saddle; back movement; pressure measurements
Introduction
Saddle slip in sports horses is a well-recognised problem that can occur
for a variety of reasons, including asymmetry in the shape of the horse’s
back [1], riders sitting crookedly [2–4], ill-fitting saddles [5,6] and hindlimb
lameness [7,8]. A pilot study revealed altered force distribution underneath
the saddle in horses with hindlimb lameness and back pain [9]. Symmetrical
thoracolumbar movement in sound horses has been demonstrated using
kinematic analysis [10,11]. However, symmetry and amplitude of the
movement of the back are influenced either by experimentally induced
transient forelimb or hindlimb lameness [12–15] or by experimentally
induced back pain [16,17]. These studies did not induce concurrent back
pain and lameness, although their coexistence is commonly recognised
clinically [18]. The majority of published information on thoracolumbar
kinematics is from treadmill studies [11,16,17], and there are limited data
on ridden sound [19–22] and lame horses [9] in ‘real-life’ conditions.
It has been observed in ridden horses that in association with hindlimb
lameness saddles may slip consistently to one side. This has encouraged
owners to try multiple saddles and additional padding to try to diminish the
saddle slip, but this has generally been ineffective [7]. Saddle slip may be
influenced by the rider’s weight and the back shape of the horse, with
greater slip occurring with lighter weight riders and in native-type horses
with round back contours [7].
A comprehensive description of the saddle kinematics in ridden sound
and lame horses outside gait laboratories has not been reported. Although
interface force–distribution data have confirmed that there are a variety of
factors that influence the movement of a saddle [6,20,23,24], there is
limited knowledge of the interrelationships between the horse, saddle and
rider and no objective assessment of saddle slip and gait irregularities in
lame horses. By evaluating the response to diagnostic analgesia, we are
able objectively to separate out the relative importance of the movement of
the horse when ridden and other factors that potentially may induce saddle
slip.
The aims of the present study were as follows: 1) to document the
frequency of occurrence of saddle slip in horses with hindlimb lameness,
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
compared with horses without hindlimb lameness; 2) to describe the effect
of lameness grade, unilateral or bilateral hindlimb lameness, multilimb
lameness (ⱖ3 lame limbs) and the coexistence of sacroiliac joint region
pain and/or thoracolumbar-sacral pain/stiffness; 3) to document the effect
of abolition of lameness by diagnostic analgesia; and 4) to determine the
relationships between saddle slip and the horse’s thoracolumbar shape
and evaluate the influence of rider weight, horse breed, type, body
condition score (BCS) and size.
It was hypothesised that saddle slip may be induced by hindlimb
lameness, with the saddle slipping most frequently to the side of the lame(r)
limb, and that the degree of saddle slip may be reduced by improvement in
the lameness by diagnostic analgesia.
Materials and methods
A prospective study was performed at the Animal Health Trust, approved
by the Ethics Committee and with informed consent of owners, between
August 2011 and August 2012. All horses that were presented for
gait assessment and were ridden by at least 2 riders were included.
Diagnosis was assigned prospectively based on the results of a
comprehensive clinical evaluation, diagnostic analgesia and imaging.
The horses were divided into the following 5 categories: Group A, hindlimb
lameness; Group B, forelimb lameness; Group C, horses with both forelimb
and hindlimb lameness; Group D, poor performance in association
with thoracolumbar-sacral and/or sacroiliac joint region pain; and Group E,
sound horses.
Horse data
Age, breed, sex, height, bodyweight, BCS [25], work discipline and the
presence of hindquarter and epaxial muscle atrophy were recorded. An
interobserver repeatability study was carried out on 10 horses for BCS,
to confirm that the method could be used practically. In addition, an
intraobserver repeatability study was performed, with 5 horses assessed
3 times in random order. A variance of less than 1% was obtained.
1
Saddle slip and lameness
L. Greve and S. J. Dyson
Assessment of thoracolumbar shape and symmetry
ventral to the dorsal midline (Fig 1). Type 1 back shape was defined as
having a ratio ⱕ0.30 (Fig 1a), type 2 back shape a ratio of 0.31 ⱕ 0.35
(Fig 1b), type 3 back shape a ratio of 0.36 ⱕ 0.40 (Fig 1c) and type 4 back
shape a ratio of ⱖ0.41 (Fig 1d).
The thoracolumbar shape and symmetry were measured at the level of the
18th (T18), the 13th (T13) and the 8th (T8) thoracic vertebrae, identified by
palpation of the ribs, and at a site one-third of the distance between the
point of the elbow and the point of the shoulder (shoulder region). A
Flexible Curve Rulera was shaped around the dorsum, perpendicular to
the dorsal midline, to follow the body contours. The resultant shape was
drawn on graph paper. A single investigator (L.G.) performed all the
measurements. Repeatability of the measuring technique was tested with
a pilot repeatability study on 3 differently shaped and sized horses
measured 10 times in random order, followed by 5 measurements in
random order of an additional 10 horses (measurement error ⫾2 mm). The
minimal detectable difference outside of the measurement error was
established using coefficients of variation (CV) of 4, 8 and 12% (95%
confidence interval [CI]) across all horses [26], and the number of horses
with asymmetries greater than a CV of 4, 8 and 12% (95% CI) was
determined. Asymmetries between left and right sides were confirmed by
rotating the Flexible Curve Ruler by 180° in a horizontal plane and
comparing it with the predrawn curve. All measurements were performed
with the horses standing squarely on a level surface, before exercise.
Preliminary data had indicated that alterations in stance could alter
measurements slightly and that measurements acquired soon after
exercise varied compared with before exercise.
Description of lameness characteristics and
saddle slip
All horses were examined by one experienced clinician (S.J.D.) moving in
hand, on the lunge and ridden, and the lameness was graded in each
circumstance (0 = sound, 2 = mild, 4 = moderate, 6 = severe and 8 =
nonweightbearing) [27]. The horses were evaluated when ridden by the
owner and at least one experienced rider from the Animal Health Trust. The
lameness was graded at sitting and rising trot on both left and right
diagonals, on the left and right reins, and when performing specific
movements, such as 10 m diameter circles to the left and right. The
lameness was graded before and after diagnostic analgesia for each
circumstance [27]. Diagnostic analgesia was performed in all lame limbs.
Rider straightness, rider weight, the grade of saddle slip, whether it
occurred with more than one rider, and whether saddle slip was influenced
by the direction of movement or by the diagonal on which the rider was
sitting were recorded. Both authors assessed saddle slip by consensus.
The same rider rode the horse before and after diagnostic analgesia. The
grade of saddle slip after lameness had been abolished was recorded.
Photographs and video recordings were obtained.
A pilot study to determine accuracy of detection of saddle slip had
previously been performed, which had involved placing markers on horses,
saddles and riders. All horses were videoed being ridden in a straight line.
The presence or absence of saddle slip was determined without and with
markers by 3 people independently. There was complete agreement
Thoracolumbar shape categories
The thoracolumbar shape at each measurement site was divided into the
following 4 categories: type 1, concave; type 2, straight; type 3, convex;
and type 4, very convex. The grading system was based on the ratio
between the horizontal distances between left and right sides 3 and 15 cm
c)
7 9 11 13 15 17 19 21 23
-27-25 -23-21-19-17-15-13-11-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 17 19 21 23 25 27
0
Back shape 3
-1
convex
-2
(0.36–0.40)
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
-17 (cm)
The distance ventral to the dorsal midline (cm)
The distance ventral to the dorsal midline (cm)
a)
-23 -21 -19 -17 -15 -13 -11 -9 -7 -5 -3 -1 1 3 5
0
Back shape 1
-1
concave
-2
(0.21–0.30)
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
-17 (cm)
The distance ventral to the dorsal midline (cm)
The distance ventral to the dorsal midline (cm)
b)
d)
-27-25-23-21-19-17-15-13-11-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 17 19 21 23 25 27
-27-25-23 -21-19-17-15-13-11-9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 17 19 21 23 25 27
0
0
Back shape 4
-1
-1
Back shape 2
-2
very convex
-2
straight
-3
(0.41–0.49)
-3
(0.31-0.35)
-4
-4
-5
-5
-6
-6
-7
-7
-8
-8
-9
-9
-10
-10
-11
-11
-12
-12
-13
-13
-14
-14
-15
-15
-16
-16
-17 (cm)
-17 (cm)
Fig 1: Four categories of the thoracolumbar shape. The grading system is based on the ratio between the horizontal distances between left and right sides 3 and 15 cm ventral to the
dorsal midline. The black and grey lines represent the range of ratios within each shape type. Type 1, concave, defined as having a ratio ⱕ0.30 (a); type 2, straight, with a ratio of 0.31
ⱕ 0.35 (b); type 3, convex, with a ratio of 0.36 ⱕ 0.40 (c) and type 4, very convex, with a ratio ⱖ0.41 (d).
2
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
Saddle slip and lameness
L. Greve and S. J. Dyson
a)
b)
in the thoracolumbar region; 8) concurrent hindlimb lameness and
close/impinging spinous processes (improved gait was seen after local
analgesia of the spinous processes); 9) unilateral gluteal muscle atrophy
and/or epaxial muscle atrophy; and 10) tension in the epaxial musculature.
For horses in Groups A and C, Spearman’s rank correlation was used to
test for association between the grade of lameness and the following
factors: 1) grade of saddle slip; 2) the tendency of the saddle to slip towards
the sound or less lame hindlimb; 3) sex; 4) age; 5) breed; 6) work discipline;
7) BCS; and 8) weight/height ratio.
For all horses in Groups A and C, Spearman’s rank correlation was used to
test for association between saddle slip and the following factors: 1) the
back shape at the shoulder, T8, T13 and T18; and 2) the effect of having a
similar or wider back shape at the level of T13 compared with T18 (horses
were selected for inclusion if the back contour at T13 ⱖ T18). All statistical
analyses were made using SPSS Statistics 20c, with significance set at
P<0.05.
Results
Fig 2: Caudal images of a horse ridden in straight lines on the left rein (a) and on a left
circle (b). There is saddle slip to the right, which was worse in circles compared with
straight lines.
between the 3 observers, and for observations made with or without
markers.
An overall saddle slip grade was obtained for each horse using a scale
from 0 to 2: grade 0, no saddle slip at any gaits; grade 1, saddle slip at the
trot and canter on one or both reins (Fig 2); and grade 2, obvious saddle slip
at trot and canter on one or both reins, such that the rider intermittently
had to stop the horse and straighten the saddle. The saddle slip grade was
applied to the lightest weight rider for all horses. The saddle slip was also
assessed subjectively in different circumstances (e.g. straight lines and
circles, and with riders of different bodyweights). In 3 horses, the force
distribution and magnitude underneath the saddle was measured using a
CONFORMatb pressure mat [28].
Assessment of the saddle fit
The tree of the saddle was checked for evenness and symmetry. The
left–right symmetry of the panels and presence of lumps or depressions
were recorded [1]. The saddle area was palpated carefully for any signs of
focal muscle soreness. An experienced clinician evaluated the saddle fit
visually and following the ridden examination. Focal areas of reduced
sweating in the saddle area was recorded [29]. The saddle type (tree,
flexible or rigid, ⫾gullet) and any special flocking, pads and numnahs used
were recorded.
Data analysis
The proportion of horses with saddle slip and hindlimb lameness, forelimb
lameness and a combination was determined. Saddle slip was compared
among Groups A, B, C, D and E using Cochran’s Q test, a chi-squared test or
Fisher’s exact test, as appropriate.
For all horses in the study, Spearman’s rank correlation was used to test
for association between saddle slip and the following factors: 1) unilateral
hindlimb lameness; 2) bilateral hindlimb lameness; 3) concurrent unilateral
hindlimb and forelimb lameness; 4) 3-limb lameness; 5) 4-limb lameness;
6) unilateral or bilateral hindlimb lameness and concurrent sacroiliac
joint region pain, verified by periarticular diagnostic analgesia [30];
7) concurrent hindlimb lameness and the presence of osseous pathology
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
There were 11 sound horses and 117 with lameness or poor performance.
The horses ranged in age from 5 to 17 years (mean 8.72 years, median 8
years) and comprised 92 geldings and 36 mares. The duration of lameness
ranged from 0 to 12 months (mean 1 month, median 1.5 months). Horses
were used for dressage (n = 32), showjumping (n = 26), eventing (n = 29),
general purposes (n = 40; horses used for unaffiliated competitions were
classified as general purpose) and endurance (n = 1). Breeds comprised
Warmbloods (n = 56), Thoroughbreds (n = 9), Thoroughbred crosses
(n = 28), cobs (n = 6), ponies (n = 15) and others (n = 14).
The horses ranged in weight from 286 to 914 kg (mean 568 kg, median
574 kg), in height from 117 to 183 cm (mean 167 cm, median 170 cm) and
the weight/height ratio ranged from 1.9 to 4.8 kg/cm (mean 3.4 kg/cm,
median 3.4 kg/cm). The BCS was 1 (n = 1), 2 (n = 10), 3 (n = 106) and 4
(n = 11). No horses with a well-fitted saddle had focal areas of reduced
sweating in the saddle region. Thirty-nine horses had saddle slip,
comprising 34 horses with grade 1 and 5 with grade 2, including 2 induced
by an asymmetric saddle. Thirteen of 39 riders (33%) had appreciated the
presence of saddle slip prior to the clinical investigation. The lameness
groups are summarised in Figure 3, together with the number of horses
with saddle slip for each lameness group. Twenty horses had unilateral
hindlimb lameness and 51 horses had bilateral hindlimb lameness. The
hindlimb lameness grade when ridden ranged from 1 to 6; the most
frequent lameness grade was 2 (n = 33). In 3 horses, hindlimb lameness
grade was at least one grade different when the rider changed from sitting
on one diagonal to the other, irrespective of whether the horse was on the
left or right rein, and this influenced the tendency for the saddle to slip.
The weight of the normal rider of horses with saddle slip associated with
hindlimb lameness ranged from 47 to 80 kg (mean 63 kg, median 65 kg).
Five riders sat crookedly. The weight of the riders (n = 4) from the Animal
Health Trust ranged from 43 to 60 kg (mean 56 kg, median 60 kg).
Saddle slip
There was complete consensus between the authors in assessment of
saddle slip. Saddle slip occurred with at least 2 riders in all the horses with
saddle slip. In horses with saddle slip which was abolished by resolution of
hindlimb lameness, saddle slip was consistently greatest with a lighter
weight rider (n = 37); however, when saddle slip was related to an
asymmetrical saddle, slip was greater with a heavier weight rider (n = 2). In
Group A, the saddle consistently slipped to one side in 20 of 36 horses
(56%); 18 of 35 horses (51%) had saddle slip in Group C, compared with one
of 26 (4%) in Group B, none of 20 (0%) in Group D and none of 11 (0%) in
Group E. The association between saddle slip and hindlimb lameness was
significant (Spearman’s r = 0.548, P<0.001). The association between
saddle slip and horses with hindlimb lameness alone (r = 0.354, P<0.001)
and horses with hindlimb lameness and coexistent forelimb lameness
(r = 0.254, P = 0.004) was significant.
Objective relationship between saddle slip
and lameness
There was a significant difference in the occurrence of saddle slip among
Groups A, B, C and D (P<0.001; Fig 3). For all horses, there was a significant
3
Number of horses
Saddle slip and lameness
L. Greve and S. J. Dyson
26
26
24
24
22
22
20
20
18
18
16
16
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
Group A:
HL Iameness
without
coexistent FL
lameness
Group B:
FL Iameness
without
coexistent HL
lameness
Group C:
Concurrent FL
and HL
lameness
Group D:
Back and/or SI
region pain
positive association between the presence of saddle slip and bilateral
hindlimb lameness (r = 0.344, P<0.001), unilateral hindlimb lameness (r =
0.286, P = 0.001), concurrent unilateral hindlimb and unilateral forelimb
lameness (r = 0.222, P = 0.012) and concurrent bilateral hindlimb lameness
and sacroiliac joint region pain (r = 0.220, P = 0.013). The association
between saddle slip and 3-limb lameness (r = 0.116, P = 0.191), 4-limb
lameness (r = 0.098, P = 0.269) and coexistent unilateral hindlimb lameness
and sacroiliac joint region pain (r = 0.012, P = 0.890) was nonsignificant.
There was a significant association between the presence of saddle slip and
tense epaxial muscles in the thoracolumbar region (r = 0.358, P<0.001) and
between unilateral hindquarter muscle atrophy and/or epaxial muscle
atrophy (r = 0.274, P = 0.002). There were significant associations between
the presence of saddle slip and both hindlimb lameness and concurrent
osseous pathology in the thoracolumbar region (r = 0.436, P<0.001) and
hindlimb lameness and improvement in clinical signs after local analgesia of
close/impinging spinous processes (r = 0.341, P<0.001). Horses with
unilateral hindquarter muscle atrophy and/or epaxial muscle atrophy (r =
0.472, P<0.001) and horses with sacroiliac joint region pain (r = 0.290, P =
0.001) were more likely to have tense epaxial muscles in the thoracolumbar
region compared with horses in Group B (r = -0.250, P = 0.005), in which the
association was negative.
For all horses in Groups A and C, there was no significant association
between the grade of saddle slip and lameness grade (r = -0.179, P = 0.136),
nor was there a significant association between the lameness grade and the
tendency of the saddle to slip towards the sound or less lame hindlimb
(r = -0.136, P = 0.260). The causes of hindlimb lameness are summarised in
Table 1, together with the number of horses with saddle slip for each cause.
Objective relationship between saddle slip and
horse data
There was no significant association between saddle slip and breed (r =
-0.069 P = 0.565), BCS (r = 0.069, P = 0.570), weight/height ratio (r = 0.151,
P = 0.210), work discipline (r = -0.064, P = 0.596), sex (r = -0.150, P = 0.211)
or age (r = 0.087, P = 0.472).
Association between back shape and saddle slip
Subjectively, only minor asymmetries <2 cm between left and right sides
were observed by rotating the Flexible Curve Ruler through 180° in a
4
Group E:
Sound horses
Fig 3: The frequency of saddle slip within the 5
categories of horses. Open columns represent horses
without saddle slip and filled columns horses with
saddle slip consistently to one side before lameness
was abolished by diagnostic analgesia.
Abbreviations: FL, forelimb; HL, hindlimb;
and SI, sacroiliac joint.
horizontal plane and comparing it over the predrawn curve. Greater
asymmetries were observed in horses without saddle slip than in horses
with saddle slip.
The mean typical measurement error for each level (shoulder, T8, T13
and T18) across all horses included in the pilot repeatability study
resulting in minimal detectable difference in back shape between left and
right sides was 0.6 cm for a CV of 4%, 1.2 cm for a CV of 8% and 1.8 cm for
a CV of 12%. All the horses with saddle slip had asymmetries between the
left and right sides of less than a CV of 8% (1.2 cm) measured at the level
of the shoulder region, T8, T13 and T18. Five horses had asymmetries
greater than a CV of 8% (1.2 cm) in the saddle region, and none had
saddle slip.
There was no significant association between saddle slip and the type of
back shape at the shoulder, T8, T13 or T18 (r = 0.128, P = 0.289), nor was
there a significant association between having a similar type of back shape
at T8, T13 and T18 and saddle slip (r = 0.112, P = 0.352) or having one or less
difference in the type of back shape among T8, T13 and T18 (r = 0.150, P =
0.211). However, there was a significant positive association between
saddle slip and horses with a wide back shape at T13 (defined as having a
back contour at T13 ⱖ T18; r = 0.340, P = 0.004). There was also a
significant positive association between horses having one or less
difference in the type of back shape among T8, T13 and T18 and a wide back
shape at T13 (r = 0.288, P = 0.015).
Factors affecting saddle slip associated with
hindlimb lameness
Thirty-seven horses had saddle slip caused by hindlimb lameness. The
saddle slipped to the side of the lame or lamer hindlimb when the horse was
worked in straight lines, going large around the arena and also in circles of
20 m diameter in most horses (32 of 37 [86%]). The direction of the saddle
slip was associated with the rein on which the horse appeared most lame in
18 of 37 horses (49%). However, this was complicated by the fact that some
of the horses (13 of 37 [35%]) going large or in a 20 m circle appeared lamer
with the lame limb on the outside, whereas on a 10 m circle the horse
appeared lamer with the lame limb on the inside. However, the difference in
appearance of the lameness did not alter the direction of saddle slip. Saddle
slip was present on both reins in 6 of 37 horses (16%) and on only one rein
in 31 of 37 (84%).
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
Saddle slip and lameness
L. Greve and S. J. Dyson
TABLE 1: The causes of hindlimb lameness and prevalence of saddle slip in 71 horses with hindlimb lameness that were ridden by at least 2 people
The causes of hindlimb lameness and other causes of lameness or poor performance
Bilateral PSD and FL lameness
Bilateral PSD and SI pain
Bilateral PSD
Unilateral CD and TMT OA
Unilateral FT OA and FL lameness
Bilateral PSD and impinging/overriding 14th–15th to 16th–17th thoracic SPs (one improved with
infiltration of local anaesthetic solution around the impinging/overriding SPs; one was not blocked)
⫾ OA 15th–16th and 16th–17th thoracic APJs
Bilateral PSD and SI pain and impinging 10th–15th thoracic SPs (one improved with infiltration of local
anaesthetic solution around the impinging SPs; one was not blocked) ⫾ OA 15th–16th and
16th–17th thoracic APJs
Bilateral PSD and SI pain and FL lameness
Unilateral PSD and FL lameness
Unilateral TMT/CD OA and bilateral PSD
Unilateral TMT/CD OA and FL lameness
Bilateral TMT/CD OA
Unilateral FT OA and middle patellar desmitis
Unilateral FT OA and bilateral PSD
Unilateral CD OA
Bilateral TMT/CD OA and OA 15th–16th thoracic APJs
Unilateral talocalcaneal joint OA, DDFT injury and old fracture of right tuber coxae and FL lameness
Bilateral MTP OA and unilateral lateral oblique sesamoidean desmitis and FL lameness
Lateral suspensory branch desmitis, apical sesamoid fracture of lateral PSB and bilateral PSD; close
SPs between the 13th and 18th thoracic vertebrae (improved with infiltration of local anaesthetic
solution around the close SPs) and OA 16th-17th and 17th-18th thoracic APJs; old fracture of the
caudoventral aspect of the 4th cervical vertebra
Unilateral medial collateral desmitis of DIP, unilateral PSD and FL pain
Unilateral accessory desmitis of SL, bilateral PSD and FL lameness
Unilateral accessory desmitis of SL, bilateral PSD and FL lameness; close/impinging SPs of first to 3rd
lumbar vertebrae*
Bilateral PSD, SI pain and impinging 10th–15th thoracic SPs (improved with infiltration of local
anaesthetic solution around the close SPs) and OA 15th–16th and 16th–17th thoracic APJs and OA
caudal cervical APJs
Unilateral PSD, SI pain, impinging SPs of the 13th thoracic to 2nd lumbar vertebrae (improved with
infiltration of local anaesthetic solution around the impinging SPs) and OA 15th-16th and
16th-17th thoracic APJs
Bilateral PSD, SI pain and impinging SPs of the 12th thoracic to 3rd lumbar vertebrae (improved with
infiltration of local anaesthetic solution around the impinging SPs) and FL lameness
Unilateral PSD
Unilateral FT OA and unilateral PSD
Unilateral lateral collateral desmitis of MTP
Unilateral displaced fractures of the distal aspect of the navicular bone and OA caudal cervical APJs
and FL lameness
Bilateral PSD, SI pain and asymmetric OA of APJs between the 15th–16th and 16th–17th thoracic
vertebrae, supraspinous ligament injury from 15th to 17th thoracic vertebrae* and FL lameness
Total
Number of
horses with
the injury
Number of
horses with
saddle slip
Percentage
with
saddle slip
13
8
7
4
2
2
5
4
2
2
2
2
38
50
29
50
100
100
2
2
100
6
4
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
17
25
50
100
100
100
100
100
100
100
100
100
1
1
1
1
1
1
100
100
100
1
1
100
1
1
100
1
1
100
2
1
1
1
0
0
0
0
0
0
0
0
1
0
0
71
37
52
Abbreviations: APJ(s) = articular process joint(s); CD = centrodistal joint; DDFT = deep digital flexor tendon; DIP = distal interphalangeal joint; FL = forelimb; FT =
femorotibial joint; MTP = metatarsophalangeal joint; OA = osteoarthritis; PSB = proximal sesamoid bone; PSD = proximal suspensory desmopathy; SI = sacroiliac
joint region; SL = suspensory ligament; SP(s) = spinous process(es); and TMT = tarsometatarsal joint. *Infiltration of local anaesthetic solution around the
close/impinging SPs was not performed.
Saddle slip was consistently greater in circles compared with straight
lines (37 of 37 horses [100%]), irrespective of the appearance of the
lameness (Fig 2). Lameness was worse when the rider sat on the diagonal of
the lame(r) limb in the stance phase in 11 of 37 horses (30%), but this was
associated with greater saddle slip in only 3 horses. Saddle slip was
consistently greater in rising trot compared with sitting trot (37 of 37) and
was remarkably reduced when riding without stirrups (4 of 4). In canter, the
saddle slip was similar to or greater than in rising trot. The saddle slip was
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
consistently less with a heavier rider in 37 horses ridden by 2 riders (Rider 1
= 43 kg and Rider 2 ⱖ60 kg), resulting in >17 kg difference in bodyweight,
but the grade (0–2) of saddle slip did not change between riders.
Diagnostic analgesia and ill-fitting saddles
Diagnostic analgesia abolishing the lameness did not eliminate the saddle
slip in 2 horses, one with hindlimb lameness and one with forelimb
5
Saddle slip and lameness
lameness; both had an ill-fitting saddle. When ridden with correctly fitting
saddles, no saddle slip was apparent.
Force distribution measurements
Two horses with lameness and saddle slip that were assessed with a
CONFORMatb pressure mat exhibited an asymmetric pressure distribution
underneath the saddle. The mean pressure in the quadrant of the lamer
hindlimb during the lamer diagonal stance phase was significantly lower
compared with the corresponding pressure in the quadrant of the sound or
less lame hindlimb during the sound or less lame diagonal stance phase.
Another horse with bilateral hindlimb lameness exhibited an almost
symmetric pressure distribution underneath the saddle; there was no
saddle slip.
When the horses with saddle slip were re-evaluated following diagnostic
analgesia that abolished the lameness, the difference in pressure
underneath the saddle between lame and sound diagonal stance
disappeared, the amplitude of the sinusoidal curve increased and the
craniocaudal excursion of the centre of pressure (COP) increased, whereas
the right–left excursion and sideways movement of the saddle decreased.
All findings from the pressure measurements correlated with the clinical
assessments.
Discussion
In accordance with our hypotheses, saddle slip was induced by hindlimb
lameness in 37 of 71 horses (52%). The saddle slip was eliminated when the
hindlimb lameness was abolished by diagnostic analgesia in 37 of 38 (97%),
verifying a causal relationship. Although no association was found between
the severity of lameness and saddle slip, horses with severe lameness
when exercised in hand were not evaluated ridden and were therefore not
included in the study. To an untrained observer, some of the horses with
obvious saddle slip when ridden appeared clinically normal, and only a
skilled, experienced clinician recognised subtle lameness. Riders were
commonly surprised by the complete abolition of saddle slip and
transformation in work quality when lameness was eliminated by
diagnostic analgesia, emphasising that saddle slip may highlight the
presence of low-grade and subclinical lameness. This indicates that even
subtle lameness can influence a horse’s entire way of moving. One horse
ridden by an experienced rider, examined 2 months prior to the
commencement of the study, had no overt lameness, but had grade 2
saddle slip and was presented for that reason. Although no overt lameness
could be seen, the horse’s performance improved substantially following
intra-articular analgesia of the tarsometatarsal joint, which abolished the
saddle slip completely (S. J. Dyson, unpublished data).
Our findings demonstrated that saddle slip can also occur because of an
asymmetrical (or ill-fitting) saddle. In 2 horses, the saddle slip was
unchanged after lameness was abolished by diagnostic analgesia, which
makes it highly unlikely that it was induced by lameness. Both horses were
also ridden with correctly fitting saddles and no saddle slip was apparent.
Although saddle slip is often a manifestation of hindlimb lameness, it can
also occur due to asymmetrical muscling of the horse’s back, asymmetrical
position of the rider [3] or asymmetry of the biomechanical function of the
horse, but based on our results these causes are less common than
hindlimb lameness.
Only 13 riders of 39 horses with saddle slip had recognised saddle slip
prior to the clinical investigation. However, in all except one horse with
saddle slip, riders from the Animal Health Trust were able to feel saddle slip.
Better education of riders may be required to recognise saddle slip,
especially because it may be an important indicator of the presence of
lameness. Five of the normal riders in the present study sat crookedly and
could have induced saddle slip; however, a similar degree of saddle slip was
seen when ridden by riders from the Animal Health Trust, who all sat
squarely when riding a variety of different horses without saddle slip.
Some movement of the saddle can potentially be detected in horses free
from lameness. In 7 Grand Prix dressage horses free from lameness ridden
on a treadmill in rising trot, there was saddle rotation around the vertical
axis away from the supporting hindlimb [20]. Alternation of the force
between right and left was also seen in the trajectory of the COP [19]. In the
present study, the saddle slip caused by hindlimb lameness was obvious
6
L. Greve and S. J. Dyson
and occurred with at least 2 riders. The saddle slip was consistently more
pronounced with a lighter weight rider, despite the lameness being less
obvious, presumably because a lighter rider is less able to stabilise and
maintain a straight position of the saddle. However, when saddle slip was
related to an asymmetrical saddle, slip was greater with a heavier weight
rider. This observation was based on only 2 horses, but mirrors previous
observations (S. J. Dyson, unpublished data). A heavier rider may
exacerbate the uneven pressure caused by the unequal thickness and
shape of the panels of the saddle. We also observed that the saddle slip
associated with lameness was much less in sitting trot or when riding
without stirrups compared with rising trot. This may be because in rising
trot the rider induces some rotation, which exacerbates sliding of the
saddle. Riders impose more force in the stirrups in rising trot compared
with sitting trot [31], although there were no significant differences in peak
forces under the saddle in rising and sitting trot [32]. However, when forces
on the back were calculated using kinematics of a rider, there was a
significant difference in peak vertical force between rising and sitting trot
[22]. In the present study, a heavier rider was more effective than a lighter
rider in maintaining stability of the saddle in sitting trot. However, in canter
saddle slip was sometimes greater than in trot, probably related to the
asymmetrical 3-beat gait, which impairs the rider’s ability to stabilise the
saddle despite sitting.
Saddle slip associated with hindlimb lameness was increased in circles
compared with straight lines. Low-grade hindlimb lameness is often
accentuated when a horse is ridden, especially in circles of approximately
10 m diameter [8]. Assessment of movement of the trunk and tubera coxae
in horses free from lameness was compared in straight lines and in circles
on the lunge in unridden horses using inertial measurement units [33].
There were significant repeatable patterns of asymmetry, which potentially
may be magnified in the face of lameness and alter forces on the saddle and
rider. Based on the results of the present study, there is clearly a complex
interaction between the size of a circle and its effect on the degree of
hindlimb lameness and its characteristics, and whether the lameness is
worse on the outside or inside of a circle, and saddle slip.
We demonstrated that the shape of the horse’s back had an influence on
saddle slip, with ‘rounder’ horses at the level of T13 being more at risk. This
may reflect greater dorsoventral displacement at T13, which appears to be
the site that comes closest to the lowest back line. The maximal range of
vertical displacement occurs at this site, where the equine body centre of
mass is aligned with the rider’s centre of mass [34,35]. However, there was
no association between the BCS and saddle slip. A large proportion of the
horses in the study were BCS 3 [25]. Use of a more sensitive method of
condition scoring, such as the 9-point scale [36], may have permitted
further differentiation among horses within BCS 3.
In our study, the saddle usually slid towards the side of the lamer
hindlimb, but sometimes towards the less lame or nonlame limb. When
saddle slip occurred towards the side of the lamer limb, this was usually
associated with the lamer limb on the outside of a 20 m circle. In contrast,
when the saddle slid towards the sound or less lame hindlimb, this was with
the lamer limb on the inside of a circle. We need to understand better the
biomechanical changes in gait that occur to cause these 2 different
patterns of saddle movement and to establish the interrelationship
between the symmetry and amplitude of equine in vivo back movement,
the saddle movement and lameness in a variety of movement conditions.
Combining conventional techniques for lameness assessment with back
kinematics data using inertial measurement units mounted on the saddle,
the rider and the horse [35] and force measurements under the saddle [37],
alongside measurements of back muscle activity using electromyography
[38,39] and ultrasonographic evaluation of multifidus [40], may help to
improve basic understanding of vertebral biomechanics and the changes
that occur with lameness.
The Flexible Curve Ruler is widely used in the saddle-fitting industry and
has been considered to be a reliable tool. However, there has been no
scientific validation prior to the present study. Our data indicate that using
strict consistency in technique (the horse standing squarely on a
horizontal, level surface, acquiring measurements before exercise at
reliably identified predetermined sites), accurate, repeatable data can be
obtained. The ruler is prone to fatigue, and regular replacement is
recommended to ensure consistency of results. However, the potential
consequences of different patterns of work prior to back shape
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
Saddle slip and lameness
L. Greve and S. J. Dyson
measurements have yet to be investigated. We also need to determine the
speed with which body shape may change over time, influenced by type
and intensity of work, skeletal maturity, work discipline and nutrition.
We have previously demonstrated that hindlimb lameness can cause
back stiffness [9]. Following diagnostic analgesia to abolish lameness, there
was increased back mobility, assessed both subjectively and objectively
using a Pliance pressure mat. The present study provided further evidence
that following diagnostic analgesia to eliminate hindlimb lameness, there
was an improved range of movement through the horse’s back and
abolition of saddle slip. This was also confirmed objectively in 3 horses by
using a pressure mat, which demonstrated increased cranial–caudal
excursion of the COP and decreased sideways movement of the COP, and
the difference in pressure between the lame and sound diagonal stance
phases disappeared.
Limitations of the study
This study had some limitations. The horses were a referral population
and therefore may not be typical of the general horse population, in which
there may be greater occurrence of musculoskeletal asymmetries. The
prevalence of crooked riders and saddle-fitting problems may not
necessarily reflect the general population. The study was not performed
blinded, which could potentially have introduced bias. There were only 39
horses with saddle slip in the study, in 37 of which saddle slip was caused by
hindlimb lameness. This was not enough to allow investigation of the
relationships between the grade and direction of saddle slip and the source
of pain causing lameness. We need to gain a better understanding of
the biomechanical changes that occur with lameness that induce
saddle slip. Combining clinical diagnosis with inertial measurement unit
measurements in a larger number of horses would enable us to establish
patterns related to the site of pain causing lameness, back movement and
saddle slip. Although there was no relationship between the presence of
saddle slip and the degree of lameness in the present study, horses that
were severely lame in hand were not ridden and were therefore not
included in the study. This may potentially have influenced the results. A
large proportion of horses had bilateral hindlimb lameness; it is difficult
to grade bilateral lameness accurately [27]. One horse ridden by a
professional rider had grade 2 saddle slip towards the lame hindlimb
abolished by diagnostic analgesia. However, the horse was assessed by
only one rider due to its potentially dangerous behaviour and was not
included in the study.
The back shape measurements were obtained in standing horses from
predetermined anatomical locations and therefore do not represent the
equine back shape in its entirety and in a dynamic situation. By combining
the Flexible Curve Ruler measurements with 3-dimensional back shape
scanning Artecd, alongside Horse Weight Measuring Tapee, it may be
possible to evaluate the back in its entirety and also to measure
quantitatively the change in back shape that may occur with work and over
time. This was a single-point study; however, most horses were
investigated over 2–3 days, and the presence or absence of saddle slip
were consistent features. A proportion of horses were re-evaluated during
the study period after treatment of lameness. In those horses in which
lameness resolved, saddle slip invariably disappeared also. There were
only 2 horses in which saddle slip was associated with an ill-fitting saddle,
but the findings recorded are consistent with previous observations
(S. J. Dyson, unpublished data).
Conclusions
Based on the present study, there is evidence that saddle slip occurs in a
high percentage of horses with hindlimb lameness. Moreover, saddle slip
may highlight the presence of low-grade and subclinical hindlimb
lameness. Saddle slip is usually blamed on saddle fit and horse shape. Our
findings emphasise the need for education of owners, veterinarians,
physiotherapists, trainers, riders and saddle fitters that saddle slip is
frequently an indicator of lameness, not necessarily a manifestation of an
ill-fitting saddle or asymmetric shape of the horse’s back. It appears that
saddle slip as a manifestation of hindlimb lameness has previously been
underestimated. In many horses hindlimb lameness goes unrecognised,
and early recognition of lameness is important for appropriate treatment
and rapid return to work. Detection of saddle slip provides an opportunity
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd
for the owner, riders and trainers to detect low-grade and subclinical
lameness, with important welfare consequences.
Authors’ declaration of interests
There are no conflicts of interest.
Source of funding
There are no sources of funding.
Acknowledgements
We thank the many referring veterinary surgeons without whom this study
would not have been possible, the Saddle Research Trust and Biosense
Medical.
Authorship
Both authors contributed to all parts of the study.
Manufacturers’ addresses
a
Ati 90 cm, Taiwan.
Tekscan, Boston, Massachusetts, USA.
c
SPSS Inc., Chicago, Illinois, USA.
d
Steinbichler Scanning Technology, Bromsgrove, UK.
e
WINtape, China.
b
References
1. Harman, J. (1999) Tack and saddle fit. Vet. Clin. N. Am.: Equine Pract. 15,
247-261.
2. Lagarde, J., Kelso, J.A., Peham, C. and Licka, T. (2005) Coordination dynamics of
the horse-rider system. J. Mot. Behav. 37, 418-424.
3. Symes, D. and Ellis, R. (2009) A preliminary study into rider asymmetry within
equitation. Vet. J. 181, 34-37.
4. Clayton, H.M., Kaiser, L.J., dePue, B. and Kaiser, L. (2011) Centre of pressure
movements during equine assisted activities. Am. J. Occup. Ther. 65, 211216.
5. de Cocq, P., van Weeren, P.R. and Back, W. (2006) Saddle pressure measuring:
validity, reliability and power to discriminate between different saddle-fits. Vet.
J. 172, 265-273.
6. Meschan, E.M., Peham, C., Schobesberger, H. and Licka, T.F. (2007) The
influence of the width of the saddle tree on the forces and the pressure
distribution under the saddle. Vet. J. 173, 578-584.
7. Dyson, S. (2010) Poor performance and lameness. In: Diagnosis and
Management of Lameness in the Horse, 2nd edn., Eds: M.W. Ross and S.J.
Dyson, Elsevier, St Louis, Missouri. pp 920-925.
8. Dyson, S. (2012) How to recognise hindlimb lameness: an obvious lameness to
subtle gait abnormalities. In: Proceedings of the American Association Equine
Practitioners Focus Meeting on Hindlimb Lameness, Oklahoma City. CD Rom,
pp 2-9.
9. Byström, A., Dyson, S. and Murray, R. (2011) Saddle pressure patterns are
altered by diagnostic analgesia in ridden horses with poor performance.
Proceedings 50th British Equine Veterinary Association Congress, Equine
Veterinary Journal Ltd, Fordham. p 181.
10. Audigié, F., Pourcelot, P., Degueurce, C., Denoix, J.M. and Geiger, D. (1999)
Kinematics of the equine back: flexion-extension movements in sound trotting
horses. Equine Vet. J. 30, 210-213.
11. Johnston, C., Holm, K.R., Erichsen, C., Eksell, P. and Drevemo, S. (2004)
Kinematic evaluation of the back in fully functioning riding horses. Equine Vet. J.
36, 495-498.
12. Buchner, H.H., Savelberg, H.H., Schamhardt, H.C. and Barneveld, A. (1996)
Head and trunk movement adaptations in horses with experimentally induced
fore- or hindlimb lameness. Equine Vet. J. 28, 71-76.
13. Pourcelot, P., Audigié, F., Degueurce, C., Denoix, J.M. and Geiger, D. (1998)
Kinematics of the equine back: a method to study the thoracolumbar
flexion-extension movements at the trot. Vet. Res. 29, 519-525.
7
Saddle slip and lameness
14. Gómez Alvarez, C.B., Wennerstrand, J., Bobbert, M.F., Lamers, L., Johnston, C.,
Back, W. and van Weeren, P.R. (2007) The effect of induced forelimb lameness
on thoracolumbar kinematics during treadmill locomotion. Equine Vet. J. 39,
197-201.
15. Gómez Alvarez, C.B., Wennerstrand, J., Bobbert, M.F., Lamers, L., Johnston, C.,
Back, W. and van Weeren, P.R. (2008) The effect of induced hindlimb lameness
on thoracolumbar kinematics during treadmill locomotion. Equine Vet. J. 40,
147-152.
16. Wennerstrand, J., Johnston, C., Roethlisberger-Holm, K., Erichsen, C., Eksell, P.
and Drevemo, S. (2004) Kinematic evaluation of the back in the sport horse with
back pain. Equine Vet. J. 36, 707-711.
17. Wennerstrand, J., Gómez Alvarez, C.B., Meulenbelt, R., Johnston, C., van
Weeren, P.R., Roethlisberger-Holm, K. and Drevemo, S. (2009) Spinal
kinematics in horses with induced back pain. Vet. Comp. Orthop. Traumatol.
22, 448-454.
18. Zimmerman, M., Dyson, S. and Murray, R. (2011) Close, impinging and
overriding spinous processes in the thoracolumbar spine: the relationship
between radiological and scintigraphic findings and clinical signs. Equine Vet. J.
44, 178-184.
19. Fruehwirth, B., Peham, C. and Schobesberger, H. (2004) Evaluation of pressure
distribution under an English saddle in walk, trot and canter. Equine Vet. J. 36,
754-757.
20. Byström, A., Rhodin, M., von Peinen, K., Weishaupt, M.A. and Roepstorff, L.
(2009) Basic kinematics of the saddle and rider in high-level dressage horses
trotting on a treadmill. Equine Vet. J. 41, 280-284.
21. de Cocq, P., Prinsen, H., Springer, N.C., van Weeren, P.R., Schreuder, M., Muller,
M. and van Leeuwen, J.L. (2009) The effect of rising and sitting trot on back
movements and head-neck position of the horse. Equine Vet. J. 41, 423-427.
22. de Cocq, P., Duncker, A., Clayton, H., Bobbert, M., Muller, M. and van Leeuwen,
J. (2010) Vertical forces on the horse’s back in sitting and rising trot. J. Biomech.
43, 627-631.
23. Byström, A., Rhodin, M., von Peinen, K., Weishaupt, M.A. and Roepstorff, L.
(2010) Kinematics of saddle and rider in high-level dressage horses performing
collected walk on a treadmill. Equine Vet. J. 42, 340-345.
24. Byström, A., Stalfelt, A., Egenvall, A., Von Peinen, K., Morgan, K. and
Roepstorff, L. (2010) Influence of girth strap placement and panel flocking
material on the saddle pressure pattern during riding of horses. Equine Vet. J.
42, Suppl. 38, 502-509.
25. Carroll, C.L. and Huntingdon, P.J. (1988) Body condition scoring and weight
estimation of horses. Equine Vet. J. 20, Suppl. 1, 41-45.
26. Hopkins, W.G. (2000) Measures of reliability in sports medicine and science.
Sports Med. 30, 1-15.
8
L. Greve and S. J. Dyson
27. Dyson, S. (2011) Can lameness be reliably graded? Equine Vet. J. 43, 379382.
28. Ferguson-Pell, M., Nicholson, G., Lennon, P. and Bain, D. (2001) Comparative of
pressure mapping systems (2): cushion testing. Proceedings of the 24th
Rehabilitation Engineering and Assistive Technology Society of North America
Conference, Arlington, Virginia. pp 289-291.
29. von Peinen, K., Wiestner, T., von Rechenberg, B. and Weishaupt, M.A.
(2010) Relationship between saddle pressure measurements and clinical
signs of saddle soreness at the withers. Equine Vet. J. 42, Suppl. 38, 650653.
30. Dyson, S. and Murray, R. (2003) Pain associated with the sacroiliac joint region:
a clinical study of 74 horses. Equine Vet. J. 35, 240-245.
31. van Beek, F., de Cocq, P., Timmermann, M. and Muller, M. (2012) Stirrup forces
during horse riding: a comparison between sitting and rising trot. Vet. J. 193,
193-198.
32. Peham, C., Kotschwar, A., Borkenhagen, B., Kuhne, S., Molsner, J. and Baltacis,
A. (2010) A comparison of forces acting on the horse’s back and the stability of
the rider’s seat in different positions at trot. Vet. J. 184, 56-59.
33. Starke, S., Willems, E., May, S. and Pfau, T. (2012) Vertical head and trunk
movement adaptations of sound horses trotting in a circle on a hard surface.
Vet. J. 193, 73-80.
34. Buchner, H.H., Obermuller, S. and Scheidl, M. (2001) Body centre of mass
movement in the lame horse. Equine Vet. J. Suppl. 33, 122-127.
35. Warner, S.M., Koch, T.O. and Pfau, T. (2010) Inertial sensors for assessment of
back movement in horses during locomotion over ground. Equine Vet. J. 42,
Suppl. 38, 417-424.
36. Henneke, D.R., Potter, G.D., Kreider, J.L. and Yeates, B.F. (1983) Relationship
between condition score, physical measurements and body fat percentages in
mares. Equine Vet. J. 15, 371-372.
37. von Peinen, K., Wiestner, T., Bogisch, S., Roepstorff, L., van Weeren, P.R. and
Weishaupt, M.A. (2009) Relationship between the forces acting on the horse’s
back and the movements of rider and horse while walking on a treadmill.
Equine Vet. J. 41, 285-291.
38. Groesel, M., Zsoldos, R.R., Kotschwar, A., Gfoehler, M. and Peham, C. (2010) A
preliminary model study of the equine back including activity of longissimus
dorsi muscle. Equine Vet. J. 42, Suppl. 38, 401-406.
39. Licka, T., Peham, C. and Frey, A. (2004) Electromyographic activity of the
longissimus dorsi muscles in horses during trotting on a treadmill. Am. J. Vet.
Res. 65, 155-158.
40. Stubbs, N.C., Hodges, P.W., Jeffcott, L.B., Cowin, G., Hodgson, D.R. and
McGowan, C.M. (2006) Functional anatomy of the caudal thoracolumbar
and lumbosacral spine in the horse. Equine Vet. J. 38, Suppl. 36, 393-399.
Equine Veterinary Journal •• (2013) ••–•• © 2012 EVJ Ltd