By Narda G. Robinson, DO, DVM, MS, FAAMA

Extracorporeal shockwave therapy (ESWT) has fast become the darling of animal rehabilitators. When this modality first came on the scene, it produced far more noise and discomfort than it does today. Modifications in shockwave equipment and energy protocols have largely eliminated the need for general anesthesia.¹ Clinical targets of ESWT can reach beyond recalcitrant wounds and disorderly joints to assist in the recovery of injured nerves and compressed spinal cords.

How does it work?

ESWT sends strong acoustic impulses into tissue, producing pressures that rapidly rise and fall. This biphasic sequence kickstarts reparative cell-signaling pathways into gear, especially those in fibroblasts. Through "mechanotransduction," fibroblasts convert the mechanical energy of pressure changes into biologically based restorative responses that build and repair.

The fact that fibroblasts respond to mechanical forces by activating their metabolism was initially discovered by Helene Langevin, MD, director of the National Center for Complementary and Integrative Health (NCCIH), and a team of researchers at the University of Vermont. In so doing, Dr. Langevin found that acupuncture signaling begins at the needle-tissue interface.³ This phenomenon helps us understand how other physical medicine modalities, such as ESWT, support cellular survival, proliferation, and differentiation.⁴ That is, pummeling cells with shockwaves gets them going, too.

Clinical applications

ESWT has long been sought for orthopedic issues, such as tendinitis, fractures, osteoarthritis, and general musculoskeletal pain problems.⁵ More recently, research indicates that ESWT offers hope for patients with neurologic diagnoses.⁶ Applying acoustic waves to an injured spinal cord augments the repair, protection, and regeneration of nerve fibers.

Mechanistically, the initial increase in inflammation from the barrage of pressure changes incites a significant down-regulation of expression of acute-phase pro-inflammatory cytokines.⁷ Brain-derived neurotrophic factor (BDNF) levels increase, as well. This protein plays crucial roles in the growth, survival, and maintenance of nerve cells in the brain and spinal cord. For example, BDNF supports synaptic plasticity and the interconnectivity of neurons, which expands individuals' ability to adapt to environmental stimuli. ESWT may also reduce spasticity and improve ambulation, urologic function, and quality of life.

Patients with peripheral nerve injury (PNI) may benefit from ESWT at least in part from the stimulation of stem cell proliferation and differentiation. As stated by Cao et al., "ESWT can induce nerve regeneration via accelerating the removal of damaged axons, promoting the proliferation of Schwann cells and enhancing axonal regeneration."⁸ Experimental animal studies have begun to test different dosing levels for PNI recovery, elucidating ideal frequencies and intensities of stimulation for problems such as sciatic nerve damage.⁹

Could ESWT help those with brain injury? Animal models of ischemic stroke have shown that ESWT can inhibit neurologic dysfunction and reduce the volume of brain infarct post-stroke. Cerebral blood flow levels increase, with no adverse effects noted.¹⁰

Veterinary clinical research

Clinical trials of ESWT in large and small animals are growing in number. Equine orthopedic applications include osteoarthritis, thoracolumbar pain, navicular syndrome, tendinopathy, and proximal suspensory desmopathy.¹¹ Investigators are working to determine optimal parameters for speeding the repair of bones, tendons, ligaments, and wounds.

A systematic review published in 2022 evaluated the strength of research for ESWT in horses, dogs, and cats and noted the following: "The review revealed that only weak scientific evidence exists for favorable effects in conditions affecting bones, ligaments, tendons, and muscles in horses and dogs. No scientific article on the use of shockwave therapy in cats was available. Reasons for the weak scientific evidence were that studies were few, most involved only a small number of animals, many had methodological problems, or, when favorable results were reported, they were not replicated in independent studies. Thus, in sport and companion animals, the scientific evidence for the clinical effects of ECSWT in horses, dogs, and cats is limited. For a few indications, notably short-term pain relief, ligament ailments, and osteoarthritis, some results appear promising, warranting further exploration in high-quality studies."¹²

Safety

What is the safety profile we should think about when treating patients with ESWT? When treating horses, "Safe, efficient application of ESWT can often be facilitated with light, standing sedation (as permitted under sanction guidelines for actively competing horses), patient restraint, and potentially earplugs, particularly in rooms with tiled or stone walls that amplify noise reverberation. The use of earplugs/hearing protection for the veterinarians/technicians administering the ESWT and/or holding the equine patient has also been advised due to its loud, ballistic noise and the potential (although unproven) ability to induce hearing loss."¹³

Additional research is needed to determine, more specifically, how many shockwave pulses to use, at what frequency and energy flux density, and with which probe. Like photomedicine therapy, "doses" of ESWT are typically provided by the commercial device manufacturer, and many lack rigorous research substantiation.

Contraindications mentioned in veterinary papers include focusing shockwaves on tumors, weakened bones, open growth plates, active infection, and bodily cavities where air or gas exists (e.g. the thorax and abdomen). Caution is advised for pregnant patients and those with severe coagulopathy.

Importantly, some have asked whether practitioners should avoid treating cancer patients altogether, or if avoiding the tumor might suffice.

The authors of a 2019 paper in Supportive Care in Cancer noted this: "Malignant tumors in the treatment area have to be seen as a contraindication for the use of ESWT treatment. Cancer itself—in the form of the underlying disease—is not a contraindication for the treatment with radial and focused shock wave therapy with low or high energy. Plantar fasciitis and calcaneal spurs, calcified shoulder, tennis elbow or Achilles tendinopathy, and delayed healing and chronic wounds are typical approved standard indications for ESWT, and are allowed when the malignant tumor is not in the treatment area. There are also other musculoskeletal and non-musculoskeletal indications (e.g. myofascial syndrome, erectile dysfunction, polyneuropathy, and lymphedema) that are relevant for cancer survivors. These indications are recommended by the International Society for Medical Shockwave Treatment (ISMST) for "common empirically tested clinical use" and as exceptional indications/expert indications." ¹⁴

From an occupational safety perspective, one final note of caution: Practitioners should consider how the audible clicking from ESWT devices may adversely affect those in the treatment area. Some individuals who are sensitive to auditory stimuli may experience a feeling that they are about to have a seizure, reminiscent of the condition known as "reflex epilepsy," in which certain sounds, especially when emitted at regular intervals, could become epileptic triggers.

Narda G. Robinson, DO, DVM, MS, FAAMA, practices osteopathic medicine and veterinary medicine. Dr. Robinson taught science-based integrative medicine at the Colorado State University College of Veterinary Medicine and Biomedical Sciences for 20 years. In 2016, Robinson established her academy in Fort Collins, Colo., where she teaches medical acupuncture, integrative rehabilitation, medical massage, and other integrative medical approaches. Dr. Robinson plans to offer programs in Sidney, British Columbia, beginning in 2026. Columnists' opinions do not necessarily reflect those of Veterinary Practice News.

References

1. Joseph GL, Duerr FM, Zhou T, et al. Use of a novel shockwave trode results in better patient acceptance in awake canine patients treated for musculoskeletal disease. Front Vet Sci. 10.1249592.
2. Ryskalin L, Morucci G, Natale G, et al. Molecular mechanisms underlying the pain-relieving effects of extracorporeal shockwave therapy: a focus on fascia nociceptors. Life (Basel). 2022;12(5):743.
3. Langevin HM, Churchill DL, and Cipolla MJ. Mechanical signaling through connective tissue: a mechanism for the therapeutic effective acupuncture. The FASEB Journal. 2001;15(12):2275-2282.
4. Frairia R and Berta L. Biologic effects of extracorporeal shock waves on fibroblast. A review. Muscles Ligaments Tendons J. 2012;1(4):138-147.
5. Ryskalin L et al. Op cit.
6. Opara J, Dymarek R, Sopel M, et al. Extracorporeal shock wave therapy (eSWT) in spinal cord injury – a narrative review. J Clin Med. 2024; 13, 5112.
7. Leister I, Mittermayr R, Mattiassich G, et al. The effect of extracorporeal shockwave therapy in acute traumatic spinal cord injury on motor and sensory function within six months post-injury: a study protocol for a two-arm, three-stage adaptive, prospective, multi-center, randomized, blinded, placebo-controlled clinical trial. Trials. 2022 Apr 1; 23:245.
8. Cao B, Tang X, Liu C, et al. Unlocking new Frontiers: The cellular and molecular impact of extracorporeal shock wave therapy (ESWT) on central nervous system (CNS) disorders and peripheral nerve injuries (PNI). Experimental Neurology. 2025;384:115052.
9. Guo J, Hai H, and Ma Y. Application of extracorporeal shock wave therapy in nervous system diseases: a review. Front Neurol. 2022;13:963849.
10. Guo J et al. Ibid.
11. Johnson SA, Richards B, Frisbie DD, et al. Equine shock wave therapy – where are we now? Equine Veterinary Journal. 55(4)593-606.
12. Boström A, Bergh A, Hyytiainen H, et al. Systematic review of complementary and alternative veterinary medicine in sport and companion animals extracorporeal shockwave therapy. Animals. 2022, 12(22), 3124.
13. Johnson SA et al. Ibid.
14. Crevenna R, Mickel M, Keilani M. Extracorporeal shock wave therapy in the supportive care and rehabilitation of cancer patients. Support Care Cancer. 2019 Nov;27(11):4039-4041. doi: 10.1007/s00520-019-05046-y. Epub 2019 Aug 24. PMID: 31446484; PMCID: PMC6803573.