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The Role of Manual
Therapies in Equine
Pain Management
Kevin K. Haussler, DVM, DC, PhD
Beyond all doubt the use of the human hand, as a method of reducing human
suffering, is the oldest remedy known to man; historically no date can be given
for its adaptation.
John Mennell, MD
The use of touch, massage, or manipulation of painful articulations or tense muscles is
arguably one of the oldest and most universally accepted forms of therapy to relieve
pain and suffering.
1
Firmly grasping an acutely injured thumb after a misdirected
hammer blow or rubbing a sore muscle or stiff joint after a long-day’s work are simple
and often effective methods of providing short-term pain relief in humans. Similarly,
animals lick, scratch, or rub wounds or areas of irritation on themselves or their
offspring in an apparent attempt to reduce pain and suffering. Horses are known to
respond favorably to grooming, to stretch, roll on their backs, and rub up against
objects, presumably because these activities provide some sense of comfort. Over
time, both lay and licensed practitioners have developed a spectrum of manual
methods to provide varying levels of pain relief to both humans and animals. However,
most organized medicine often remains skeptical of any purported effects of massage
or other forms of manual therapy, and routinely ostracizes practitioners that apply
these techniques.
2
In the last few decades, considerable advances have been
made in conducting investigations into plausible mechanisms of action and scientific
reviews of the clinical efficacy of manual therapy in pain management.
All forms of manual therapy involve the application of the hands to the body, with
a diagnostic or therapeutic intent.
3
Abdominal and rectal palpation, soft tissue and
bony palpation of musculoskeletal structures, or moving a joint through its expected
range of motion are considered essential diagnostic techniques used routinely in
veterinary medicine (Fig. 1). Touch therapies, massage, physical therapy, osteopathy,
Gail Holmes Equine Orthopaedic Research Center, Department of Clinical Sciences, College of
Veterinary Medicine and Biomedical Sciences, Colorado State University, 300 West Drake Road,
Fort Collins, CO 80523, USA
E-mail address: Kevin.Haussler@ColoState.edu
KEYWORDS
Manual therapy Touch Stretching Massage Mobilization
Manipulation Pain
Vet Clin Equine 26 (2010) 579–601
doi:10.1016/j.cveq.2010.07.006 vetequine.theclinics.com
0749-0739/10/$ – see front matter Ó2010 Elsevier Inc. All rights reserved.
and chiropractic are techniques that have been developed for treatment of musculo-
skeletal disorders in humans and transferred for use in horses. Each treatment method
has a unique origin and different proposed biomechanical or physiologic effects;
however, all forms of manual therapy are characterized by applying variable grada-
tions of manual force and degrees of soft tissue or articular displacement (Fig. 2).
4
The goal of all manual therapies is to influence reparative or healing processes within
the neuromusculoskeletal system, which often includes pain relief.
The therapeutic effects of manual therapies may be generalized to the entire body
by inducing relaxation or altering behavior; regional effects may include alterations in
pain perception or neuromuscular control; or effects may be localized to specific
tissues and cellular responses.
3
The challenge for practitioners is in selecting the
most appropriate and effective form of manual therapy to produce the desired phys-
iologic effect within an individual patient, such as increasing joint range of motion,
reducing pain, or promoting general body relaxation. Anecdotally, all forms of manual
therapy have varying reported levels of effectiveness in humans and horses. Unfortu-
nately, most claims are not supported by high levels of evidence from randomized,
controlled trials or systematic reviews of the literature. The purpose of this article is
provide a brief description and overview of the scientific literature on the efficacy,
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Fig. 1. Joint mechanics as it relates to active and passive joint range of motion. The physi-
ologic limit demarcates active versus passive joint range of motion. The paraphysiologic
space is defined by the elastic barrier and the anatomic limit of the articulation. Inducing
motion beyond the anatomic limit of the joint induces tissue damage and results in joint
subluxation or luxation.
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Fig. 2. Joint mechanics as it relates to the site of action of various manual therapies. Touch
therapies and massage do not typically induce joint motion, whereas all forms of exercise
occur within the active range of joint motion. Passive stretching and joint mobilization
occur within the passive range of joint motion. Joint manipulation, characterized by
a high-velocity, low-amplitude thrust, occurs outside of the limits of passive joint motion;
within the paraphysiologic space.
Haussler
580
safety, and mechanisms of action of the different manual therapy techniques
commonly applied to horses, with a specific focus on their role in acute and chronic
pain management.
ANTINOCICEPTIVE EFFECTS OF MANUAL THERAPIES
Pain represents a series of complex molecular, cellular, physiologic, physical, and
behavioral attributes and interactions.
5
Nociception involves the processes of trans-
duction (at the sensory nerve ends), transmission (via peripheral sensory nerves),
modulation (within the spinal cord), projection (via ascending pain pathways), and
pain perception (within the thalamus and cerebral cortex).
6
The exact mechanisms
by which manual therapies relieve pain are unknown; however, the various forms of
manual therapy may influence the nociceptive processes at each of these levels.
The problem, in part, is in defining and objectively measuring the primary cause of
musculoskeletal pain.
1
Transduction may be altered by local biochemical changes
induced by massage that modulates local blood flow and oxygenation of tissues.
7
Pinching the skin at the site of an injection is a form of a manually induced counterir-
ritant or afferent stimulation that acts to reduce the perception of pain associated with
percutaneous injections. The transmission of nociceptive signals may be altered by
mechanical and neurophysiologic mechanisms associated with spinal manipulation,
which influence primary afferent neurons from paraspinal tissues, the motor control
system, and pain processing.
8,9
Modulations of spinal pathways act to inhibit central
sensitization and influence referred pain. Peripheral and central sensitization are char-
acterized by increased sensitivity of local tissues and the spinal cord to noxious and
innocuous stimuli, which causes an increase in pain perception. Spinal manipulation
is theorized to produce an inhibitory effect mediated by induced stretching of spinal
mechanoreceptors that reduce central sensitization of the segmental dorsal horn
neurons.
8,10
Neuronal and synaptic plasticity of spinal neurons may also be influenced
by manual therapies.
11
The gate-control theory predicts that massaging a particular
area stimulates large diameter nerve fibers, which have an inhibitory input within the
spinal cord.
7
Projection of nociceptive signals may be altered by descending pain
inhibitory systems projecting from the brain to the spinal cord, which can be activated
by spinal manipulation via sympathoexcitatory effects.
12
Manual therapies may also
increase pain thresholds through the release of endorphins and serotonin and modu-
late activity within subcortical nuclei that influence mood and pain perception.
7
Pain
perception may be influenced through physical and mental relaxation.
7
Placebo or
psychological effects also play a role in human pain; however the magnitude of these
effects within the veterinarian-client-patient relationship is unknown.
13
Manual therapy is considered to produce physiologic effects within local tissues, on
sensory and motor components of the nervous system, and at a psychological or
behavioral level.
3
It is likely that specific manual therapy techniques are inherently
more effective than others in addressing each of these local, regional, or systemic
components.
14
The challenge is in choosing the most appropriate form of manual
therapy or combination of techniques that will be efficacious for an individual patient
with specific musculoskeletal disabilities (Table 1). If soft tissue restriction and pain
are identified as the primary components of a musculoskeletal injury, then massage,
stretching, and soft tissue mobilization techniques are indicated for increasing tissue
extensibility (Fig. 3).
15
However, if the musculoskeletal dysfunction is localized to
articular structures, then stretching, joint mobilization, and manipulation are the
most indicated manual therapy techniques for restoring joint range of motion and
reducing pain.
16
Equine Manual Therapies 581
Local tissue effects produced by manual therapy techniques relate to direct
mechanical stimulation of skin, fascia, muscles, tendons, ligaments, and joint
capsules.
17
Direct mechanical loading of tissues can alter tissue healing, the physical
properties of tissues (eg, elongation), and local tissue fluid dynamics associated with
extracellular or intravascular fluids. Normal tissue repair and remodeling relies on
mechanical stimulation of cells and tissues to restore optimal structural and functional
properties, such as tensile strength and flexibility. Nonspecific back pain is most likely
related to a functional impairment and not a structural disorder; therefore, many back
problems may be related to muscle or joint dysfunction with secondary soft tissue irri-
tation and pain generation.
18
Soft tissue contractures and adhesions are unwanted
effects associated with musculoskeletal injuries and postsurgical immobilization.
19
Stretching exercises or direct mechanical mobilization of the affected tissue can be
used to elongate contracted or fibrotic connective tissues to improve soft tissue
extensibility and increase joint range of motion.
15
Tissue viability is highly dependent
on its vascular and lymphatic supply, which is often compromised as a result of
mechanical disruption or ischemia. Soft tissue or joint mobilization may facilitate
flow to and from the affected tissues, help to reduce pain and edema, and decrease
joint effusion.
20
Joint manipulation can improve restricted joint mobility and may
reduce the harmful effects associated with joint immobilization and joint capsule
contractures. Limb and joint mobilization can also have direct mechanical effects on
nerve roots and the dura mater, which may have clinical application in the treatment
of perineural adhesions and edema.
21
Table 1
Potential indications for application of various equine manual therapy techniques
Manual Therapy Technique Indications
Touch therapies Pain
Massage Muscle hypertonicity, soft tissue restriction, pain
Stretching Soft tissue restriction, joint stiffness
Soft tissue mobilization Soft tissue restriction, pain
Joint mobilization Joint stiffness, pain
Joint manipulation Joint stiffness, pain, muscle hypertonicity
Fig. 3. Soft tissue mobilization of the skin overlying the trunk. The skin and superficial fascia
is mobilized in cranial-caudal and medial-lateral directions to assess or treat any soft tissue
restrictions in movement.
Haussler
582
Joint mobilization and manipulation are believed to produce different physiologic
effects; however, the evidence in humans is mixed. Manipulation has been shown
to immediately reduce spontaneous myoelectrical activity and paraspinal muscle
spindles, whereas mobilization has not.
22,23
For neck pain in humans, manipulation
produces significant reductions in pain and disability, compared with mobilization.
24
However, both joint mobilization and manipulation increase cervical range of motion
to a similar degree.
25
Other studies report that neither manipulation nor mobilization
are beneficial or significantly different for mechanical neck disorders.
26
For acute
low back pain in humans, there is moderate evidence that spinal manipulation
provides more short-term pain relief than does mobilization.
16
It has been theorized
that spinal manipulation preferentially influences a sensory bed, which, in terms of
anatomic location and function, is different from the sensory bed influenced by spinal
mobilization techniques.
27
Manipulation may particularly stimulate receptors within
deep intervertebral muscles, whereas mobilization techniques most likely affect
more superficial axial muscles. In horses, spinal manipulation increased the dorsoven-
tral displacement of the trunk and applied force, which indicate increased spinal flex-
ibility and increased tolerance to pressure in the thoracolumbar region of the equine
vertebral column, compared with mobilization alone.
28,29
The literature suggests
that any stimulus that activates high-threshold receptors within the periarticular
tissues has the potential to initiate unique neurologic reflexes associated with joint
manipulation.
30,31
Tissue manipulation has the additional effect of stimulating regional or systemic
changes in neurologic signaling related to pain processing and motor control.
32
Manual therapy can provide effective management of pain and neuromuscular deficits
associated with musculoskeletal injuries, alterations in postural control, and locomo-
tory issues related to antalgic or compensatory gait.
3
In response to chronic pain or
stiffness, new movement patterns are developed by the nervous system and adopted
in an attempt to reduce pain or discomfort. Long after the initial injury has healed,
adaptive or secondary movement patterns may continue to persist, which predispose
adjacent articulations or muscles to injury.
18
Activation of proprioceptors, nocicep-
tors, and components of the muscle spindles provide afferent stimuli that have direct
and widespread influences on components of the peripheral and central nervous
systems that directly regulate muscle tone and movement patterns.
18
The various
forms of manual therapy are believed to affect different aspects of joint function via
diverse mechanical and neurologic mechanisms.
4
Alterations in articular neurophysi-
ology from mechanical or chemical injuries can affect both mechanoreceptor and
nociceptor function via increased joint capsule tension and nerve ending hypersensi-
tivity.
33
Mechanoreceptor stimulation induces reflex paraspinal musculature hyperto-
nicity and altered local and systemic neurologic reflexes. Nociceptor stimulation
results in a lowered pain threshold, sustained afferent stimulation (ie, facilitation),
reflex paraspinal musculature hypertonicity, and abnormal neurologic reflexes. Touch
and light massage preferentially stimulate superficial proprioceptors, whereas any
technique that involves deep tissue massage, stretching, muscle contraction, or joint
movement has the potential to stimulate deep proprioceptors.
3
Massage, stretching,
and joint mobilization are also considered to affect more superficial epaxial muscles,
such as the longissimus muscle, and to have a multisegmental effect. In contrast,
manipulation preferentially stimulates mechanoreceptors within deep multifidi
muscles and has a more segmental focus.
27
Joint manipulation can affect mechano-
receptors (ie, Golgi tendon organ and muscle spindles) to induce reflex inhibition of
pain and muscle relaxation and to correct abnormal movement patterns.
8
Because
of somatovisceral innervation, mobilization and manipulation within the trunk has
Equine Manual Therapies 583
possible influences on the autonomic system and visceral functions; however, the clin-
ical significance and repeatability of these effects are largely unknown.
34,35
The effects of touch or massage on psychological issues such as behavior or
emotion are often dismissed as an insignificant component of the overall healing
process in patients.
3
Promoting general body relaxation and reducing anxiety may
be significant components of pain management protocols.
36
Behaviors related to
pain, depression, or fear are associated with patterned somatic responses, which
may be manifest as generalized changes in muscle tone, autonomic activity, or altered
pain tolerance. Other psychological factors associated with manual therapies include
placebo effects and patient satisfaction. Unfortunately, the role of placebo effects in
horses and their owners is currently unknown.
THERAPEUTIC TOUCH
The physical act of touching another human being or an animal can induce physiologic
responses and is often considered therapeutic.
37
Interacting with animals during
animal-assisted therapy sessions has been shown to reduce blood pressure and
cholesterol, decrease anxiety, improve a person’s sense of well-being, and cause
a significant reduction in pain levels in humans.
38,39
Similarly, petting a horse or
a dog can cause physiologic changes within the animal itself.
40
In humans, therapeutic
touch is used by nurses to nurture premature infants, for supportive care in cancer or
terminally ill patients, and for support of the bereaved.
41
Recognized touch therapy
techniques in humans include Healing Touch, Therapeutic Touch and Reiki.
42
These
techniques are considered a form of energy-based therapy in which practitioners
move their hands over the body but do not contact the patient or use a gentle touch
over certain areas of the body with the goal of facilitating physical, emotional, mental,
and spiritual health. Human patients often use touch therapies for relaxation, stress
reduction, and symptom relief. Mechanical devices or squeeze machines have also
been developed to induce deep pressure or full-body compression, which induce
calming behaviors in both autistic human patients and animals.
43,44
Reviews of
controlled studies in humans evaluating effectiveness of touch therapies show prom-
ising results for pain relief, but further rigorous studies are needed to define clinical
applications and mechanisms of action.
42,45
Trials conducted by more experienced
practitioners appeared to yield greater effects in pain reduction.
In horses, touch therapies have been primarily developed and promoted by Linda
Tellington-Jones in a collection of techniques named the Tellington Touch Equine
Awareness Method (TTEAM) or Tellington TTouch.
46
Anecdotally, therapeutic touch
is considered to improve behavior, performance, and well-being of horses and
enhance the relationship between horse and rider, but no controlled studies exist to
support these claims. Similar touch therapy techniques have been used in foals at
birth to assess the effects of touch or imprint training on behavioral reactions during
selected handling procedures.
47
Conditioned foals were significantly less resistant
to touching the front and hind limbs and picking up the hind feet at 3 months of
age. Well-designed and controlled studies are needed to determine the effectiveness
of touch theories in managing behavior and musculoskeletal pain in horses.
MASSAGE THERAPY
Massage therapy is defined as the manipulation of the skin, muscle, or superficial soft
tissues either manually (eg, rubbing, kneading, or tapping) or with an instrument or
mechanical device (eg, mechanical vibration) for therapeutic purposes (Fig. 4).
Massage techniques do not typically cause movement or changes in articular
Haussler
584
positioning and include many named methods such as Swedish massage, Rolfing,
myofascial release, trigger point therapy, lymphatic drainage, and acupressure.
7
The manual techniques used in massage include effleurage, pe
´trissage, friction,
kneading, or hacking, and often vary in the depth or speed of the applied pressure
and in the specific tissues or regions of interest.
48
Massage is indicated for a wide
variety of conditions in which pain relief, reduction of swelling, or mobilization of adhe-
sive tissues are desired.
49
Massage is generally recognized as a safe intervention with
minimal adverse effects. However, deep friction, compression, or ischemic compres-
sion have been reported to produce temporary postmassage soreness or ecchymosis
in humans.
50
Massage is contraindicated for acute injuries, open wounds, and skin
infections.
48
Clinically, massage and soft tissue mobilization are believed to increase blood flow,
promote relaxation, reduce muscle hypertonicity, increase tissue extensibility, reduce
pain, and speed return to normal function; however, few controlled studies exist to
support these claims.
7,51
There are many anecdotal reports of the beneficial effects
of massage on human athletic performance; however, strong evidence in the form
of controlled studies does not exist for the effects of massage on preventing injuries,
recovery from exercise, or enhancing performance.
52
Systematic reviews suggest that
massage may be beneficial for patients with subacute and chronic nonspecific low
back pain in humans, especially when combined with exercises and education
programs.
53,54
There is moderate evidence that acupressure may be more effective
than Swedish massage for chronic low back pain.
7
Massage is also a popular adjunct
to cancer palliation and systematic reviews suggest that massage can alleviate a wide
range of cancer-associated symptoms in humans: pain, nausea, anxiety, depression,
anger, stress, and fatigue.
55,56
Unfortunately, the methodological quality of most
massage studies is poor, which prevents definitive conclusions and recommenda-
tions.
57
More research is needed to determine which type of massage is indicted
for similar clinical presentations within patients, such as higher baseline pain scores,
muscle spasms, or stress and anxiety.
7
In horses, massage therapy has been shown to be effective for reducing stress-
related behavior
40
and lowering mechanical nociceptive thresholds within the thoraco-
lumbar region.
58
A noncontrolled, clinical trial using 8 horses measured increased
stride lengths at the walk and trot before and after massage, but changes were not
significant because of the small sample size.
59
Manual lymph drainage has been
Fig. 4. Mobilization of the skin overlying the lateral scapular region using a skin-rolling
technique to assess the quality and quantity of soft tissue mobilization in the region.
Equine Manual Therapies 585
described for use in the management of lymphedema in horses; however, no
controlled studies exist evaluating its effectiveness.
60
In a clinical trial in dogs,
massage was significantly more effective in increasing lymph flow than passive flexion
and extension of the forelimb or electrical stimulation of the forelimb musculature.
61
More high-quality, objective, outcome-based evidence is needed to support the use
of massage therapy in horses.
62,63
PASSIVE STRETCHING EXERCISES
Passive stretching consists of applying forces to a limb or body segment to lengthen
muscles or connective tissues beyond their normal resting lengths, with the intent of
increasing joint range of motion and promoting flexibility.
64
Passive joint range of
motion or stretching exercises differ neurophysiologically from active joint motion or
exercise, which requires muscle activation, strength, and coordination. Active stretch-
ing involves using the patient’s own movements to induce a stretch, whereas passive
stretches are applied to relaxed muscles or connective tissues during passive soft
tissue or joint mobilization. In horses, active stretches of the neck and trunk are often
induced with baited (ie, carrot) stretches with the goal in increasing flexion, extension,
or lateral bending of the axial skeleton (Fig. 5).
65
Asking horses to produce active
stretching of specific articulations is often difficult; therefore, passive stretches are
most commonly prescribed in horses (Fig. 6).
66
Distraction or traction refers to
applying manual or mechanical forces to induce separation of adjacent joint surfaces,
which causes stretching of the joint capsule, reduced intraarticular pressure, and is
often used to reduce joint luxations (Fig. 7).
Stretching exercises vary according to the direction, velocity, amplitude, and dura-
tion of the applied force or induced movement. However, it is difficult to identify which
combination of positions, techniques, and durations of stretching are the most effective
Fig. 5. Induced active cervical range of motion using a baited stretch. Note that the horse is
positioned up against a wall to prevent lateral movement of the trunk as the hay is posi-
tioned at the girth region to induce left lateral bending of the cervical region. Active range
of motion helps to identify left-to-right asymmetries in joint range of motion.
Haussler
586
to induce increased joint range of motion and reduced pain within a specified articula-
tion.
67
Stretching should be performed slowly to maximize tissue elongation due to
creep and stress relaxation within fibrotic or shortened periarticular soft tissues.
15
Sus-
tained low-load stretching is more effective than rapid high-load stretching for altering
viscoelastic properties within soft tissues.
68
Rapid stretching may exceed the tissue’s
mechanical properties and produce additional trauma within injured tissues.
69
The
force applied during stretching exercises should be tailored to specific phases of tissue
repair.
15
During the acute inflammatory phase, stretching should be mostly avoided
because of the increased risk of tissue injury. During the regenerative and remodeling
phases of healing, tissues progressively regain tensile strength and applied manual
forces can be gradually increased. The amount of force applied during passive stretch-
ing is largely based on the patient’s response and signs of pain. Musculoskeletal injuries
are often characterized by multiple tissue involvement, each of which has a different
Fig. 6. Induced passive right lateral bending of the lower cervical region. The intervertebral
articulation of interest (eg, C5–C6) is stabilized with one hand as the head and neck of the
horse is brought into lateral bending. Gentle joint mobilization at the end range of motion
helps to localize and lateralize signs of pain, joint stiffness, and muscle hypertonicity to
specific cervical intervertebral articulations.
Fig. 7. Passive distraction of the carpus. The distal limb is passively flexed over the doctor’s
forearm to induce a distractive force to the carpal articulations and associated joint
capsules.
Equine Manual Therapies 587
healing rate and unique mechanical response to stretching. Therefore, effective
stretching programs are best tailored to address specific soft tissue injuries and not
only focused on restoring joint motion.
The duration of the applied stretch is dependent on the force applied, affected
tissue shape and size, the amount of damage or fibrosis present, and the stage of
tissue healing.
15
In humans, the recommended duration for stretching the musculo-
tendinous unit varies from 6 to 60 seconds.
69
Stretching for 30 seconds has been
shown to be significantly more effective than 15-second stretches; however, structural
and functional differences within each affected tissue makes general recommenda-
tions for stretching a particular articulation or limb difficult to establish.
70
The mode
of loading during an applied stretch varies from continuous to cyclic. Continuous or
static loading can be uncomfortable for some patients and is not recommended.
15
Cyclic or rhythmical stretching is more comfortable and physiologic as it provides
periods of tissue loading and unloading, which has biomechanical and neurologic
benefits. Cyclic loading also has cumulative effects on soft tissues as a result of incre-
mental elongation and stress relaxation within each stretch cycle; however, these
effects are maximized approximately within the first 4 cycles of loading.
69
Therefore,
recommendations for optimal passive stretching include applying 4 to 5 repetitions of
slow low-load forces held at the end range of motion of the affected tissues, with each
stretch applied and released in 30-second cycles, without inducing pain. If performed
inappropriately, stretches may cause or aggravate injuries.
71
Therefore, thorough
patient evaluation and formulation of a proper stretching program are required before
implementing any stretching exercises.
Stretching soft tissues is believed to increase joint range of motion, enhance flexi-
bility, improve coordination and motor control, increase blood flow to muscles, and
helps to prevent injuries.
72
Systematic reviews of the human literature suggest that
stretching may have beneficial effects on increasing joint range of motion, reducing
pain, and preventing work-related musculoskeletal disorders.
71,73
There is strong
evidence that stretching and strengthening exercises are effective for reducing pain,
improving function, and producing favorable long-term global effects in human
patients with subacute and chronic mechanical neck disorders.
74
Randomized studies
suggest that regular stretching increases joint range of motion (average of 8) for more
than 1 day after cessation of stretching and that the effects of stretching are possibly
greater in muscle groups with limited extensibility.
75
Regular stretching has been
shown to improve performance by increasing force, jump height, and speed.
76
Other
reviews of the literature report that there is not sufficient evidence to endorse or dis-
continue routine stretching before or after exercise to prevent injury among competi-
tive or recreational human athletes.
77–79
Because of the relatively low methodological
quality of most studies, further research is needed to determine the proper role of
stretching in human sports. Stretching combined with strengthening provides the
largest improvement in nonspecific chronic neck or low back pain in humans.
80,81
In horses, passive stretching exercises of the limbs and axial skeleton have anec-
dotal effects of increasing stride length and joint range of motion and improving overall
comfort (Fig. 8).
66
In a noncontrolled study, passive thoracic limb stretching lowered
wither height as a result of possible relaxation of the fibromuscular thoracic girdle.
82
However, a randomized controlled trial in riding school horses evaluating the effect
of 2 different 8-week passive stretching programs reported no significant changes
in stride length at the trot but had a detrimental effect of decreasing joint range of
motion within the shoulder, stifle, and hock articulations.
83
The investigators
concluded that daily stretching may be too intensive in normal horses and may actu-
ally cause negative biomechanical effects. Additional studies on the effects of different
Haussler
588
stretching techniques and frequency for specific disease processes using objective
outcome measures need to be completed before any further claims of performance
enhancement or pain reduction in horses can be made.
SOFT TISSUE AND JOINT MOBILIZATION
Mobilization is defined as manually or mechanically induced movement of articulations
or soft tissues for therapeutic purposes. Soft tissue mobilization focuses on restoring
movement to the skin, connective tissue, ligaments, tendons, and muscles with the
goal of modulating pain, reducing inflammation, improving tissue repair, increasing
extensibility, and improving function.
51
Neural mobilization techniques have been
developed to induce movement within specific spinal or peripheral nerves and the
dura mater with the intent of reducing neural adhesions and edema.
21,32
Joint mobi-
lization is characterized as nonimpulsive repetitive joint movements induced within
the passive range of joint motion with the purpose of restoring normal and symmetric
joint range of motion, to stretch connective tissues, and to reduce pain (Fig. 9).
84
Biomechanical characteristics of joint mobilization include low velocity movements,
low peak forces, and large displacements. Mobilization is typically applied with oscil-
latory forces within or at the limits of physiologic joint range of motion without impart-
ing a thrust or impulse. Mobilization is also performed within the patient’s ability to
resist the applied motion and therefore requires cooperation and relaxation of the
patient. Joint mobilization is usually applied in a graded manner, with each grade
increasing the range of joint movement. Grade 1 and 2 mobilizations are characterized
by slow oscillations within the first 25% to 50% of the available joint motion, with the
goal of reducing pain. Grade 3 and 4 mobilizations involve slow oscillations at or near
the end of available joint motion, which are used to increase joint range of motion.
Some soft tissue and joint mobilization techniques may include a hold and stretch
at the end range of motion.
Soft tissue and joint mobilization is used to assess the quality and quantity of joint
range of motion and as a primary means of treating musculoskeletal disorders. Adjunc-
tive physical therapy techniques include therapeutic exercises and rehabilitation of
Fig. 8. Induced passive thoracic limb protraction. At the end range of motion, the horse is
asked to actively extend the thoracic limb into the doctor’s hands in an effort to stimulate
neuromuscular reflexes and improve active protraction of the limb.
Equine Manual Therapies 589
neuromotor control, where manual forces are used to induce passive stretching, weight
shifting or activation of spinal reflexes, which help to increase flexibility, stimulate
proprioception and strengthen core musculature.
32,65
There is strong evidence that
a multimodal approach of cervical mobilization, manipulation, and exercise are effec-
tive for reducing pain, improving function, and producing favorable long-term global
effects in human patients with subacute and chronic mechanical neck disorders.
74
Active range of motion exercises may be more effective for acute pain reduction in
human patients with whiplash-associated disorders.
85
There is mediate evidence in
humans that mobilization and manipulation produce similar effects on pain, function,
and patient satisfaction at intermediate-term follow-up.
86
Peripheral nerve and nerve
root mobilization techniques and exercises are also used for the postoperative rehabil-
itation of low back pain.
87
Few formal studies exist to support the use of active soft tissue, joint, or spinal mobi-
lization techniques in horses.
28
Most mobilization studies in horses involve a period of
induced joint immobilization by a fixture or cast followed by allowing the horse to spon-
taneously weight bear and locomote on the affected limb, without evaluation of specific
soft tissue or joint mobilization techniques.
19
Spinal mobilization has been shown to be
effective at increasing spinal flexibility in ridden horses without clinical signs of back
pain.
29
Spinal manipulation, characterized by high-velocity, low-amplitude thrusts,
produced immediate and larger increases in displacement within treatment sessions;
whereas the effects of spinal mobilization had a delayed effect of increasing displace-
ment, which suggests 2 possibly different mechanisms of action for spinal mobilization
and manipulation.
88
Spinal mobilization is generally considered a more conservative or
low-force technique applied in acute pain conditions; whereas manipulation is theoret-
ically considered a more specific and forceful type of manual therapy that has shown
more beneficial effects for chronic neck or back pain in humans.
16
MANIPULATION
Joint manipulation is characterized by the application of a high-velocity, low-amplitude
thrust or impulse that moves a joint or vertebral segment beyond its physiologic range of
motion, without exceeding the anatomic limit of the articulation.
89
Differences in the
magnitude and rate of loading associated with mobilization versus manipulation are
likely to produce variable therapeutic effects because of the viscoelastic nature of the
Fig. 9. Spinal mobilization at the thoracolumbar junction. A ventral force is applied rhyth-
mically to assess the quality and quantity of passive joint range of motion and the joint end-
feel (ie, anatomic limit of the articulation) in extension at sequential intervertebral levels.
Haussler
590
soft tissues surrounding the vertebral column.
88,90
Spinal manipulation involves the
application of controlled thrust or impulse to articular structures within the axial skeleton
with the intent of reducing pain and muscle hypertonicity and increasing joint range of
motion.
91
Both the chiropractic and osteopathic professions use high-velocity, low-amplitude
thrusts to induce therapeutic effects in articular structures, muscle function, and neuro-
logic reflexes with the goal of increasing joint range of motion and reducing pain.
4,92
Most human chiropractic patients seek care because of headaches or spinal pain;
more than 70% have neck or lower back pain.
93
Human research has demonstrated
reductions in pain and muscle hypertonicity and increased joint range of motion after
chiropractic treatment.
16,25,94
In humans, osteopathic care significantly reduces low
back pain and effects can persist for at least 3 months.
95
Few studies have assessed
the efficacy of preventative spinal manipulation for managing chronic low back
pain.
96
The therapeutic dose of joint manipulation is varied by the number of vertebrae
or articulations treated, the amount of force applied, and the frequency and duration of
treatment. Unfortunately, there is not good scientific evidence on which to base optimal
dosage recommendations for continued care, therefore therapeutic trials are often
used on an individual basis.
97
There is low quality evidence that cervical manipulation
alone compared with a control may provide short-term pain relief following 1 to 4 treat-
ment sessions, and that 9 to 12 sessions were superior to 3 treatments for pain and
disability in patients with cervicogenic headache.
86
High-dose manipulation is superior
to low-dose manipulation for chronic low back pain in the short-term.
98
In horses, anecdotal evidence and clinical experience suggest that manipulation is
an effective adjunctive modality for the conservative treatment of select musculoskel-
etal-related disorders.
99
However, therapeutic trials of spinal manipulation are often
used because there is limited formal research available about the effectiveness of
osteopathic or chiropractic techniques in equine practice. Equine osteopathic evalu-
ation and treatment procedures have been described in textbooks and case reports,
but no formal hypothesis-driven research exists.
92,100,101
Human osteopathic tech-
niques also include highly controversial methods associated with mobilizing cranial
bones and abdominal viscera, which have questionable application to horses.
92,102
The focus of recent equine chiropractic research has been on assessing the clinical
effects of spinal manipulation on pain relief, improving flexibility, reducing muscle
hypertonicity, and restoring spinal motion symmetry. Obvious criticism has been
directed at the physical ability to even induce movement in the horse’s back. Pilot
work has shown that manually applied forces associated with chiropractic techniques
are able to produced substantial segmental spinal motion.
103
Two randomized,
controlled clinical trials using pressure algometry to assess mechanical nociceptive
thresholds in the thoracolumbar region of horses have shown that both manual and
instrument-assisted spinal manipulation can reduce back pain (or increase mechan-
ical nociceptive thresholds).
58,104
Additional studies have assessed the effects of
equine chiropractic techniques on increasing passive spinal mobility (ie, flexibility)
28,29
and reducing longissimus muscle tone.
105
The effect of manipulation on asymmetrical
spinal movement patterns in horses with documented back pain suggest that chiro-
practic treatment elicits slight but significant changes in thoracolumbar and pelvic
kinematics and that some of these changes are likely to be beneficial.
106,107
MANUAL-ASSISTED TECHNIQUES
In humans, the application of manual forces can be combined with a wide diversity
of therapeutic or medical techniques to produce varying effects. Hand-held
Equine Manual Therapies 591
spring-loaded or electromechanical devices can be used to apply single or multiple
impulses to articulations or tissues in a series of techniques named manually assisted,
mechanical force procedures. It has been reported that approximately 40 N of force is
required to activate mechanical and neurologic responses associated with spinal
manipulation.
108
Manual impulses applied to the human cervical and lumbar spine
range from 40 to 400 N and occur for 30 to 150 milliseconds. Similar amplitudes of
force have been measured with instrument-assisted manipulations (ie, 72 N to 230
N); however, the impulse occurs for a much smaller time (ie, 0.1–5.0 milliseconds). It
is hypothesized that the velocity of the applied force may be more important than
the amplitude of the applied force.
108
Randomized studies have shown similar effec-
tiveness using either manual or instrument-assisted treatment techniques.
109,110
Using a stick and mallet or similar percussive device to apply sharp mechanical forces
to dorsal spinous processes has been reported in horses to reduce back pain and
increase spinal range of motion, but controlled studies are lacking.
106
Theoretically,
there is an increased risk for injury using instrument-assisted techniques or hammers
to treat horses because of the possibility of applying excessive forces by inexperi-
enced or lay practitioners with little or no knowledge of spinal or joint biomechanics.
Joint mobilization and manipulation can be combined with sedation or general
anesthesia, which provides increased relaxation and analgesia for evaluation of subtle
joint motion restrictions or treatment of joint contractures and spinal pain, without the
influence of conscious pain or protective muscle guarding.
111
Manipulation under
anesthesia generally consists of 4 stages: sedation, mobilization/stretching/traction,
manipulation, and aftercare of active rehabilitation and additional manual therapy.
112
Indications for manipulation under anesthesia in humans include pain that will not
allow conscious manipulation, conditions that do not respond to conscious spinal
manipulation within 4 to 8 weeks, chronic joint or soft tissue fibrosis, acute myofascial
rigidity and painful inhibition, severe joint dysfunction, refractory contained disc herni-
ation, and multiple recurrences of a condition.
113
The risks of manipulation under
sedation or general anesthesia include the inability of patients to provide verbal feed-
back on pain or to resist overzealous manipulation because intrinsic guarding mech-
anisms associated with voluntary muscle contraction are absent, which can produce
an increased risk of iatrogenic injuries.
113
There is currently insufficient evidence to
make any recommendations regarding the use of manipulation under anesthesia for
chronic low back pain in humans.
112
Spinal manipulation under sedation and anesthesia has been used in horses to
address reduced joint mobility; however, controlled studies are lacking.
101,114,115
In
a case series of 86 horses, 88% of horses maintained improved ranges of pain-free
joint motion after cervical mobilization and sustained stretching at the end range of
motion while under anesthesia.
114
Similar indications and risks associated with the
mobilization or manipulation under anesthesia in humans are expected in horses.
No significant adverse effects were reported with cervical mobilization under general
anesthesia in horses.
114
Well-designed controlled studies are needed to further inves-
tigate the safety and effectiveness of these techniques in equine practice.
Manipulation combined with epidural analgesia or epidural medications consists of
segmental anesthesia with simultaneous epidural corticosteroid injection and spinal
manipulation.
111
In humans, epidural anesthesia is less costly and is associated
with fewer risks than general anesthesia, patients are able to cooperate during treat-
ment, and epidural corticosteroids reduce inflammation and reduce fibrosis and adhe-
sions, compared with manipulation under anesthesia alone. One possible indication
for using this technique in horses is severe or compensatory spinal pain or stiffness
associated with chronic limb lameness.
Haussler
592
Joint mobilization or manipulation combined with intraarticular injection of either
local anesthetic or corticosteroids has also been reported to reduce pain and inflam-
mation associated with osteoarthritis and is believed to more effectively restore joint
mobility.
111
Indications in humans include recalcitrant joint pain that prevents mobili-
zation or rehabilitation of the affected region. In horses, one possible indication
includes cervical facet osteoarthritis, where acute pain and inflammation can be
initially controlled with intraarticular facet injections; however, recurrent stiffness
and disability are common. Intraarticular injections combined with a series of spinal
manipulations, stretching, and strengthening exercises provides the opportunity to
increase pain-free cervical mobility and reduce long-term morbidly or recurrence.
Controlled clinical trials are needed to assess other possible clinical indications and
effectiveness of manipulation combined with intraarticular injections in horses.
INDICATIONS FOR MANUAL THERAPIES
Most of the current knowledge about equine manual therapies has been borrowed
from human techniques, theories, and research, and applied to horses. Therapeutic
trials are often used because of limited knowledge about the effectiveness for specific
disease conditions or the duration of action of select manual therapies in horses. The
indications for joint mobilization and manipulation are similar and include restricted
joint range of motion, muscle spasms, pain, fibrosis, or contracted soft tissues.
84
The principal indications for spinal manipulation are neck or back pain, localized or
regional joint stiffness, poor performance, and altered gait that is not associated
with overt lameness. A thorough diagnostic workup is required to identify soft tissue
and osseous disorders, neurologic disorders, or other lameness conditions that may
not be responsive to manual therapy. Clinical signs that indicate a primary spinal
disorder include localized musculoskeletal pain, muscle hypertonicity, and restricted
joint motion. This triad of clinical signs can also be found in a variety of lower limb
disorders; however, they are most evident in horses with neck or back problems. Clin-
ical signs that indicate chronic or secondary spinal disorders include regional or
diffuse pain, generalized stiffness, and widespread muscle hypertonicity. In these
cases, further diagnostic evaluation or imaging should be done to identify the primary
cause of lameness or poor performance. Manual therapy may help in the management
of muscular, articular, and neurologic components of select musculoskeletal injuries in
performance horses. Musculoskeletal conditions that are chronic or recurring, not
readily diagnosed, or are not responding to conventional veterinary care may be indi-
cators that manual therapy evaluation and treatment is needed. Manual therapy is
usually more effective in the early clinical stages of disease processes versus end-
stage disease when reparative processes have been exhausted. Joint manipulation
is usually contraindicated in the acute stages of soft tissue injury; however, mobiliza-
tion is safer than manipulation and has been shown to have short-term benefits for
acute neck or back pain in humans.
116
Manipulation is probably more effective than
mobilization for chronic neck or back pain and has the potential to help restore normal
joint motion, thus limiting the risk of reinjury.
18
Contraindications for mobilization and manipulation are often based on clinical judg-
ment and are related to the technique applied and skill or experience of the practi-
tioner.
84
Few absolute contraindications exist for joint mobilization if techniques are
applied appropriately. Manual therapy is not a cure-all for all joint or back problems
and is generally contraindicated in the presence of fractures, acute inflammatory or
infectious joint disease, osteomyelitis, joint ankylosis, bleeding disorders, progressive
neurologic signs, and primary or metastatic tumors.
84
Joint mobilization and
Equine Manual Therapies 593
manipulation cannot reverse severe degenerative processes or overt pathology. Acute
episodes of osteoarthritis, impinged dorsal spinous processes, and severe articular
instability, such as joint subluxation or luxation, are often contraindications for manip-
ulation. Inadequate physical or spinal examinations and poorly developed manipula-
tive skills are also contraindications for applying manual therapy.
113
All horses with
neurologic diseases should be evaluated fully to assess the potential risks or benefits
of joint mobilization or manipulation. Cervical vertebral myelopathy occurs because of
both structural and functional disorders.
117
Static compression caused by vertebral
malformation and dynamic lesions caused by vertebral segment hypermobility are
contraindications for cervical manipulation; however, adjacent regions of hypomobile
vertebrae may benefit from mobilization or manipulation to help restore joint motion
and reduce biomechanical stresses in the affected vertebral segments. Life-threat-
ening injuries or diseases requiring immediate medical or surgical care need to be
ruled out and treated by conventional veterinary medicine before any routine manual
therapy is initiated. However, manual techniques may contribute to the rehabilitation
of most postsurgical cases or severe musculoskeletal injuries by helping to restore
normal joint motion and function. Horses that have concurrent hock pain (eg, osteoar-
thritis) and a stiff, painful thoracolumbar or lumbosacral vertebral region are best
managed by addressing all areas of musculoskeletal dysfunction. A multidisciplinary
approach entails combined medical treatment of the hock osteoarthritis and manual
therapy evaluation and treatment of the back problem.
In humans, adverse effects or risks of complications associated with joint mobiliza-
tion are minimal. Mobilization is considered safer than manipulation.
116
Some investi-
gators suggest that given the higher risk of adverse reactions and lack of
demonstrated effectiveness of manipulation over mobilization, then manual therapists
should consider conservative mobilization, especially in human patients with severe
neck pain.
118
In humans, most adverse events associated with spinal manipulation
are benign and self-limiting.
119
Potential mild adverse effects from properly applied
manipulations include transient stiffness or worsening of the condition after treatment.
Data from prospective studies suggest that minor, transient adverse events occur in
approximately half of all patients during a course of spinal manipulative therapy.
120,121
However, these mild adverse effects do not cause patients to stop seeking manipula-
tive care. Mild adverse effects usually last less than 1 to 2 days and resolve without
concurrent medical intervention. Severe complications following spinal manipulation
are typically uncommon and estimates of the incidence range from 1 in 200,000 to
1 per 100 million manipulations in humans.
116,122,123
The most common serious
adverse events in humans are vertebrobasilar accidents, disk herniation, and cauda
equina syndrome.
120
However, there is no evidence of increased risk of vertebrobasi-
lar artery stroke associated with chiropractic care compared with primary medical
care.
124
Even though the complication rate of spinal manipulation is small, the poten-
tial for adverse outcomes must be considered because of the possibility of permanent
impairment or death.
116
The benefits of chiropractic care in humans seem to outweigh
the potential risks.
125
The risk of adverse effects associated with joint mobilization or
spinal manipulation is unknown in horses. The apparent safety of spinal manipulation,
especially compared with other medically accepted treatments for neck or low back
pain in humans, should stimulate its use in the conservative treatment of spinal-related
problems.
123,126
If an exacerbation of musculoskeletal dysfunction or lameness is
noted after spinal manipulation, then a thorough re-examination and appropriate
medical treatment should be pursued. If the condition does not improve with conser-
vative care, referral for more extensive diagnostic evaluation or more aggressive
medical treatment is recommended.
Haussler
594
FUTURE STUDIES
Further research is needed to assess the effectiveness of specific manual therapy
recommendations or combined treatments for pain management and select lameness
conditions. Currently there is no validated equine model for studying the effects of
manual therapies that would allow characterization of the anatomic, biomechanical,
neurophysiologic, pathophysiologic, cellular, or biochemical changes associated with
soft tissue and joint mobilization or high-velocity thrusts. Further understanding of the
local and systemic effects of mobilization and manipulation on pain reduction and tissue
healing is also needed. Additional studies are needed to determine the duration of the
clinical effects of manual therapies and the multimodal use of mobilization or manipula-
tion and analgesics or other pain managementstrategies. Controlled trials using different
forms of spinal manipulation (eg, manual thrusts vs instrument-assisted thrusts vs
manipulation under anesthesia) need to be done to determine which method is most
effective for addressing specific disease processes. Studies are needed to identify
which pain or patient characteristics are likely to benefit from the various forms ofmanual
therapy, either individually or in combination. New methods of objectively measuring
musculoskeletal dysfunction and further studies into the pathophysiology of chronic
pain syndromes are needed to help assess the effectiveness of manual therapies on
reducing morbidity and improving overall performance in equine athletes.
SUMMARY
A thorough knowledge of equine anatomy, soft tissue and joint biomechanics, muscu-
loskeletal pathology, tissue-healing processes, and pain mechanisms is required to
understand the basic principles and application of the various forms of manual thera-
pies for pain management. There is a notable lack of evidence for using touch,
massage, stretching exercises, and joint mobilization techniques in horses. However,
spinal manipulation has been shown in several studies to be effective for reducing
pain, improving flexibility, reducing muscle tone, and improving symmetry of spinal
kinematics in horses. Because of potential misuse and safety issues, mobilization
and manipulative therapies should be provided only by specially trained veterinarians
or licensed human manual therapists.
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