Manual therapy is a general term that refers to treatment approaches involving the hands (such as massage or chiropractic). Treatments done with the hands may also be instrument-assisted. While manual therapies are most commonly used for the treatment of somatic pain or other musculoskeletal maladies, other indications may include lymphedema, immune suppression, or visceral discomfort.

Massage techniques vary widely, ranging from the traditional kneading and stroking to deep tissue work requiring concerted pressure. The most commonly researched technique is Swedish massage, also known as classical muscular massage. Swedish massage incorporates several maneuvers, including effleurage (stroking and gliding), tapotment (percussion), petrissage (kneading), and friction massage. Effleurage involves tissue compression. Tapotment vibrates tissue, while petrissage stretches adherent fibrous tissue, and friction lengthens connective tissue to reduce contractures. Massage techniques are multicultural and share similarities; for example, Swedish massage has similarities to the Chinese manual therapy technique Tui Na. Other massage techniques include German connective tissue massage and Rolfing, a strong and sometimes painful form of “deep tissue” massage introduced in the USA.

Manual therapy frequently targets the spine. When people speak about “animal chiropractic,” “veterinary manual therapy,” or “animal adjusting,” they are usually referring to maneuvers directed to the back or neck in an effort to alleviate pain or, more generally, spinal dysfunction. Some interventions are borrowed from the human chiropractic field and incorporate mechanical devices known as adjusting tools or activators. When “activated,” this hand-held device, which resembles a metal syringe with a rubber knob at the end, delivers a rapid “thump” to the patient, roughly mimicking the action of a person applying a thumb thrust to the body. More violent and less sophisticated methods applied to horses incorporate mallets and blocks of wood intended to “drive protruding spines into line;” all such methods have, as yet, failed to demonstrate therapeutic utility in animals.

Mechanisms of Action

Massage focuses on soft tissue elements—namely, muscles and the enveloping fascia. Benefits such as stress and blood pressure reduction, normalized gastric motility, immune regulation, and amelioration of depression may share a common mechanism of action. That is, the neuromodulatory and homeostatic effects of massage likely pertain to parasympathetic nervous system stimulation.

Currently available evidence does not support the use of massage as an important therapeutic intervention in repair of muscle damage, longterm muscle relaxation, or in preparation for or recovery from exercise. The suggestion that massage may be able to induce increased blood flow, thereby making oxygen, nutrients, and bloodborne factors such as neutrophils and macrophages more accessible to damaged tissue has been studied; the majority of findings have failed to support any increase in muscle blood induced by massage in large or small muscle groups in human subjects.

Massage—also known as manual lymph drainage—can assist local lymphatic circulation (eg, lymphedema); the therapist gently strokes along lymphatic vessels and over lymph nodes in order to facilitate passive return of lymph fluid to the vascular system. Unfortunately, such effects are transient.

In contrast to slow-moving massage strokes, the rapid thrusts that characterize chiropractic manipulations have many theoretical—but no proven—mechanism(s) of action. The lack of current knowledge tends to be extrapolated into speculation, and chiropractic theories may be presented as fact. Claims are made that chiropractic manipulation activates muscle spindles, Golgi tendon organs, joint capsule mechanoreceptors, and receptors in the skin, and that simultaneous firing of multiple types of receptors modifies CNS activity, blunting nociception and normalizing muscle tone, joint mobility, and sympathetic nervous system activity. Unfortunately, there is inadequate basic science data to substantiate any of these claims. No chiropractic technique has been shown to be superior to another; none has demonstrated efficacy in controlled research in animals.

The relevance of high velocity, low amplitude thrusting maneuvers to therapeutic outcomes has been questioned. During a chiropractic manipulation, the total force applied to a particular area is not the same as the total force applied to the body. As the forces during spinal manipulative treatment increase, so does the contact area; therefore, much of the total treatment force can be taken up by nontarget-specific tissues. The effective loading of specific target sites of individual vertebrae or spinal segments is much smaller than the global measures of total force applied might suggest.

Those accustomed to hearing the “pop” or “audible” secondary to joint cavitation during high velocity manual thrusting may question the effectiveness of treatments that fail to cause joint noise. However, research indicates that audibles are not necessary for successful treatment. Activator treatments typically do not cause joint noise.

Indications

For both massage and chiropractic in veterinary patients, indications may include neck or back pain or stiffness, inability to sit straight, reduced flexibility, muscle spasms, poor performance, difficulty going up or down stairs, inability to walk or run in a straight line, and abnormal tail carriage. There are no data from well-designed scientific trials to support the utility of such interventions in dogs, cats, or horses, however.

Contraindications

Due to underreporting of adverse events in complementary therapies, the true range and incidence of risks from massage remain unknown. The lack of such reports does not necessarily indicate that a given therapy is safe. Contraindications are usually determined based on empirical evidence or on what might seem reasonable. Thus, patients who are especially fragile or ill generally require briefer and gentler treatments with less digital pressure and compression. Soft tissue techniques would not be applied directly over areas of infection, acute inflammation, tumor, recent surgical procedures, or thrombosis. Similarly, massage may not be ideal in areas of acute inflammation, skin infection, bone fracture, burn, deep vein thrombosis, or cancer.

Contraindications for chiropractic might include conditions that weaken bone or other structural elements such that applying a thrust to a vulnerable spine or limbs could lead to serious injury. Examples of deossifying or destabilizing conditions include hyperadrenocorticism, neoplasia, secondary renal hyperparathyroidism, degenerative joint disease, and disk disease. Some animal chiropractors have advocated chiropractic for an array of problems such as idiopathic lameness, intervertebral disk disease, Wobbler syndrome/cervical vertebral insufficiency, spondylosis, cauda equina syndrome, urinary incontinence, neuropathies, postsurgical rehabilitation, trauma, and organ pathology. However, many of these may actually constitute contraindications. One research-based human CAM reference places joint hypermobility, arthritis, and neurologic problems from disk disease under the heading of contraindications to chiropractic, along with cancer, infectious disease, fractures, clotting disorders, osteopenia, and osteoporosis.

Adverse Effects

Excessive pressure or sudden explosive force has the potential for injuring organs, vessels, neural tissue, or bones. Deep massage of the abdomen can damage organs (rupture/bleeding) and nerves (from direct pressure onto nerves); intense pressure could dislodge a stent or catheter or embolize thrombi. For chiropractic manipulations, although appropriate thrusting forces vary with the size of the animal and the type of joint undergoing treatment, the thrusts are not always innocuous. A heavy-handed individual can seriously harm or even kill an animal. Even milder thrusts may injure animals weakened by age, joint pathology, osteopenia, or neoplasia.

Injuries from chiropractic usually reflect trauma to the spinal cord or brain arising from impacted blood vessels, disks, or nervous tissue. Human neurologic and neurosurgical reports have revealed an association between stroke and upper cervical manipulation. In addition to high velocity techniques, deep massage or other pressing techniques in the suboccipital region have damaged vessels and caused neurologic impairment and death. Although rare, stroke from cervical chiropractic manipulation of human patients is well recognized and likely occurs more often than is reported. The mechanism of injury typically involves arterial dissection or spasm.

A study of human patients with neck pain showed that 25% of patients reported increased neck pain or stiffness following chiropractic treatment, and adverse reactions were more likely to follow higher force techniques. The study concluded that because high-force techniques failed to demonstrate superior effectiveness to low-force maneuvers, chiropractors should consider conservative manipulative procedures. Especially in geriatric or otherwise fragile animals, manual therapy techniques from the soft tissue therapy repertoire constitute safer approaches than forceful, high velocity techniques.

Controversies

From a mechanical standpoint, direct application of human chiropractic theories to animals might not be warranted. The forces on the spine of a quadruped differ from those of bipeds. Furthermore, the vertebrae of horses are the size of a human fist and are surrounded by muscle, tendon, and ligament layers several inches thick, leading to questions as to whether equine vertebrae can be manipulated at all.

Claims that spinal joints or other bones move “out of place” have not been substantiated. Even if such lesions exist, the diagnostic measures commonly used to detect them are not reproducible or reliable. The overall utility of manipulative therapy for the treatment of a condition (including its most common indication, musculoskeletal pain) has not been established.

Finally, additional controversy arises from the fact that manual therapies may be delivered by nonveterinarians. Manual therapies pose potential risks; when they are practiced by overzealous therapists with insufficient education about anatomy and pathology, the risk of injury to the patient or the practitioner increases. Unfamiliarity with animal behavior and proper restraint can lead to injury to the therapist or bystanders if the animal reacts to treatment; nonprofessionals do not carry liability insurance for such incidents.

Even so, some state legislatures have altered veterinary practice acts to accommodate nonveterinarian trade groups. These changes do not necessarily protect animals. For chiropractic care specifically, veterinarians should consider several factors before delegating care to a nonveterinarian, including whether they want to be responsible for any adverse sequelae to treatment.

Last full review/revision July 2011 by Narda G. Robinson, DO, DVM, MS, FAAMA