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Photo credit: Emily Thurner Photography for Forward Equine Veterinary Services
Extracorporeal shockwave therapy (ESWT) is a common treatment modality offered by many veterinarians for treating lameness in horses. Most veterinarians use shockwave therapy in the treatment of arthritis and ligament injuries.
ESWT produces a high-energy shockwave that applies pressure via acoustic waves to a desired tissue. This pressure triggers tissue damage, which may stimulate tissue repair and activate healing factors. [1]
Shockwave therapy is also purported to increase blood flow to the treated area, enhancing the delivery of nutrients and oxygen, which are essential for tissue repair. It is also believed to reduce pain by over-stimulating pain receptors, which can decrease their sensitivity.
Despite its widespread clinical use, there is limited scientific evidence to support the efficacy of ESWT, as there have not been large randomized controlled trials or experimental studies. [1] Further research is needed to determine the efficacy of shockwave therapy in treating various lameness conditions in horses.
Shockwave Therapy for Horses
Extracorporeal Shockwave Therapy is a non-invasive treatment used in horses to promote healing of injured soft tissue, bones, and joints. The shockwaves are waves of sound energy generated by a machine, and applied to the surface of the skin to target the underlying tissues. [1]
These shockwaves produce a focal area of high pressure in the tissue. [1] The shockwaves also trigger cavitation bubbles to form within the tissue as a result of high pressure, which then implode and produce additional energy waves. [3]
Depending on the treatment protocol, veterinarians can adjust several aspects of the shockwaves produced to maximize treatment efficacy. Adjustable features include: [1]
- Energy level
- Amount of pressure produced
- Frequency of pulses
- Duration of the pulses
- Depth of tissue penetration
Most treatment protocols advise three to six treatments at 2-3 week intervals. [4] This time period allows the body to heal the tissue damage ESWT produces. [4] ESWT requires good contact between the skin surface, so clipping the hair over the treatment area may be necessary. [4]
ESWT cannot penetrate solid structures such as the hoof wall and sole. [4] It also can only reach structures between 50 to 110 mm deep, making certain joints, such as the sacroiliac joint, inaccessible to this treatment modality. [4]
Clinical Use
The first use of shockwaves in human medicine was to treat bladder stones, utilizing the shockwaves’ capability to break up bladder stones into small fragments. [1]
Practitioners using shockwaves for this purpose noticed that bone density increased in the areas surrounding the treated area. [2] This finding led to the use of ESWT in musculoskeletal injuries.
Now, shockwaves are a common component of treatment protocols for suspensory ligament injuries and arthritis in horses. [1]
Effect on Tissues
The exact mechanism by which ESWT affects tissues is currently unknown. [1] When the shockwaves interact with tissues, the energy contained within each wave is released, causing compression and shear (tearing) forces on the surrounding tissue. [5] Some veterinarians suggest that this damage stimulates healing, resulting in improved function over time.
In bones, ESWT appears to cause local bleeding and microfractures to the bone surface, which in turn stimulates new bone formation. [1][5]
In tendons, ESWT causes similar damage to tendon cells, which can increase production of proteins and glycosaminoglycans, a critical component for tendon repair. [1][6] Studies in rats show increased production of collagen (the main component of tendons) after ESWT treatment.
In muscles, ESWT may increase the regeneration rate of muscle fibers after muscle damage. [3]
There are several studies in rabbits and rats showing that ESWT can increase angiogenesis (production of blood vessels) in injured tissues, which may lead to faster healing. [3] Some research indicates that ESWT may also have a numbing effect on nerves, reducing pain associated with lameness. [1]
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Usage & Scientific Evidence
ESWT is becoming increasingly popular with veterinarians as a modality for treating lameness cases. [7] One survey-based study reported that 37% of equine veterinarians use ESWT at least once weekly. [7]
There are several potential uses of shockwave therapy in horses including: [4]
- Tendon and ligament injuries
- Stress fractures of bone
- Osteoarthritis
- Nonhealing bone fractures
- Back pain
- Navicular syndrome
However, there is currently limited scientific evidence to support the use of ESWT in horses. [2] Additionally, the optimum number of pulses, frequency of treatment, locations of treatment, and strength of pulses are currently unknown. [1][4]
“Shockwave therapy can be used for suspensory ligament injuries and certain arthritic joints, especially when trying to support tissue healing or reduce pain without systemic medications. That said, horse owners should understand that ESWT efficacy varies by condition, and the supporting evidence is strongest for ligament desmitis, not for deeper joint or navicular issues.”
— Dr. Jennifer Skaggs, DVMEquine Veterinarian
More thorough research, including clinical trials, is necessary to validate the use of ESWT as a treatment modality for lameness.
Ligament Injuries
Veterinarians most commonly use ESWT for treating ligament injuries, particularly suspensory ligament desmitis (inflammation of a ligament). [1][7] 58% of surveyed veterinarians believe that ESWT is highly effective in treating ligament injuries in horses. [7]
Experimental studies with induced suspensory ligament injuries show promising results. One study showed improved healing on ultrasound in ESWT treated injuries compared to untreated injuries. [2]
A randomized control trial also showed that a greater proportion of horses with suspensory desmitis treated with ESWT were back in full work after one year compared to horses treated with platelet-rich plasma. [2] These types of studies provide the most convincing evidence of treatment efficacy.
There are also several case reports examining lameness and return to performance in horses treated with ESWT. Most of these studies show that around 50% of horses with suspensory desmitis treated with ESWT are sound at 6 months after treatment. [2]
The current body of research regarding ESWT treatment of ligament injuries shows promise, however more experimental studies and randomized control trials are necessary to confirm the efficacy of ESWT in treating these conditions.
Tendon Injuries
Many veterinarians use ESWT to treat tendon injuries, such as damage to the superficial and deep digital flexor tendons. [3][7] There are limited studies on the effect of ESWT on tendon injuries in horses.
One experimental study showed that ESWT treatment increased production of glycosaminoglycans and proteins in treated tendons, but these effects decreased 6 weeks after treatment. [6] Analysis of the tendon tissues under a microscope showed that ESWT disrupted the normal pattern of the tendon fibres, and that areas of disorganization were still present 6 weeks after treatment. [6]
From this study, researchers concluded that ESWT may speed up initial healing processes in injured tendons, but it may also have long-term effects including tendon fibre disorganization. [6]
Arthritis
Studies show that ESWT may be beneficial in treatment of equine osteoarthritis, and it has become a popular treatment modality in many veterinarians’ treatment protocols. [1][2] Most commonly, veterinarians use ESWT to treat arthritis of the lower hock joints (bone spavin). [1]
One study induced arthritis experimentally in the knee joints of horses, and treated some of the study population using two treatments of ESWT at two week intervals. [8] Follow-up examination showed that ESWT-treated horses had lower lameness scores than the control groups. [8] However, there were no changes in the joint fluid or cartilage in the treated joints. [8]
There are also case studies showing reduced lameness from ESWT treatment of bone spavin. [2] However, these studies did not have control groups, so the true efficacy of ESWT cannot be determined. [2]
Pain Control
Veterinarians commonly use ESWT as part of treatment protocols for back pain due to impinging dorsal spinous processes (“kissing spine”), however ESWT may also provide pain control in other locations. [1] ESWT can reduce the conduction velocity of the sensory nerves in the treatment area, reducing the ability for pain signals to reach the brain. [2]
There are several studies focused on treating back pain in horses using ESWT. One study showed a reduced response to pressure over the back 56 days after ESWT treatment. [9] Another study showed reduced lameness at 90 days after ESWT treatment, and improvements in tissue integrity during ultrasound at 120 days after treatment. [2]
There are also reports of ESWT treatment providing pain control for up to 6 months after treatment, with one study showing that 31% of horses had reduced back pain for over 6 months. [3] However, in this study, horses received multiple types of treatment, so the effect of ESWT on its own is difficult to discern. [3]
Another study examining the effect of one ESWT treatment on forelimb lameness showed that the analgesic (pain-relieving) effect of ESWT may be similar to local anesthetic in some cases, and lasts up to 2 days. [10]
Overall, these studies suggest that shockwave therapy may benefit horses by providing moderate pain control in the short-term and potentially long-term. However, many of the studies performed in horses do not have control groups, so further investigation is required to confirm these findings. [2]
Wound Healing
ESWT may help speed healing times in wounds. [2] Experimental studies where the effect of ESWT was tested on experimentally created wounds showed faster healing time, reduced granulation tissue formation, and reduced inflammation. [2]
There is also a report of using ESWT as part of a treatment protocol for burn injuries in a horse. [11] In this application, ESWT was thought to have an anti-inflammatory effect, provide pain control, and induce new vessel formation to help speed healing. [11]
The practitioners working on this case believed that the use of ESWT sped up wound healing and did not have any adverse effects on the horse. [11]
Overall, the evidence for use of ESWT in wound healing is low, as there have not been clinical trials and the experimental studies conducted had low numbers of test animals. [2]
Navicular Syndrome
Some veterinarians may use ESWT as part of their treatment protocol for navicular syndrome, a hoof condition that can cause lameness and discomfort. [1] However, there is currently limited evidence to support the use of ESWT in treating this condition. Additionally, most surveyed veterinarians perceive that ESWT is ineffective in treating navicular syndrome based on their experience. [7]
Although ESWT cannot penetrate the hoof capsule or sole, applying the machine probe to the frog can allow the shockwaves to interact with the inner structures of the hoof. [4] Applying the probe to the bulb of the heel can also have a similar effect. [2]
Most studies regarding navicular syndrome are case reports or studies following a group of horses with no control group. Many of these studies show improved lameness up to 6 months after ESWT treatment. [2] One study identified no changes on X-ray or bone scan after ESWT treatment, and suggested that the improved lameness was likely due to a pain control effect of ESWT rather than treatment of the disease process. [2]
Side Effects
Shockwave therapy should only be performed by a qualified veterinarian or under veterinary supervision to ensure it’s used safely and effectively. Improper use may increase the risk of side effects.
White Hairs
ESWT can cause overheating of the tissues, which may damage hair follicles in horses. [4] In some cases, these damaged hair follicles may permanently grow white hairs. [4] Owners concerned about their horses’ cosmetic appearance may wish to avoid ESWT use for this reason.
Microfractures
A reported consequence of ESWT is production of small microfractures on the surface of bones. [5]
One study in racing Thoroughbreds showed that use of ESWT increased the amount of microfractures in the treated area, as well as the length of the microfractures. [5]
Additionally, there are reports of excessively high pressure shockwaves causing bone fractures in rabbits. [5] Researchers believe that use of ESWT may increase microfractures in limb bones, which may increase the risk of catastrophic bone fractures in racing or high-performance animals. [5]
However, a direct association between ESWT use and catastrophic fractures has not been definitively shown.
Premature Growth Plate Closure
There are reports in laboratory animals showing that ESWT can trigger premature closure of the growth plates in growing animals. [3] For this reason, veterinarians should avoid treating areas near growth plates in young horses. [3]
Competition Use
Due to the potential pain control effects of ESWT, many competition organizations restrict the use of shockwave therapy in horses. [3] Most organizations prevent use of ESWT within 5-10 days of performance events. [3]
Organizations that currently have regulations banning or restricting the use of ESWT include: [3]
- Fédération Equestre Internationale (FEI)
- National Thoroughbred Racing Association
- US Equestrian Federation
- Equestrian Canada
Competition riders and trainers should investigate their organization’s policies on ESWT before these treatments are applied to their horses. Some organizations also require completion of a specific form by the veterinarian administering the ESWT treatment.
Frequently Asked Questions
Here are some frequently asked questions about shockwave therapy in horses:
Shockwave therapy does show measurable effects in horses for certain injuries, though overall effectiveness remains under study. Research includes small experimental trials and case reports that report improvements in suspensory ligament issues, some arthritis cases, and back pain. Large randomized trials are still lacking, so results can vary by condition and by individual horse. Many veterinarians continue to include this therapy while acknowledging that stronger evidence is needed to confirm benefits across different lameness problems.
Conditions most often treated with shockwave therapy in horses include suspensory ligament injuries, tendon injuries, arthritis of the lower hock joints, stress fractures, and certain types of back pain. Veterinarians may also consider it for nonhealing bone fractures and navicular syndrome, though evidence for these uses is weaker. Ligament injuries remain the area with the strongest clinical support and higher reported success.
Changes inside a horse’s tissues during and after shockwave treatments involve controlled micro-damage that stimulates healing processes. High-energy sound waves create pressure and cavitation bubbles that implode, producing compression and shear forces in tissue. This microtrauma can encourage new blood vessel formation, increase production of proteins and glycosaminoglycans in tendons, and create small bone microfractures with local bleeding that may prompt new bone formation.
Concerns for using shockwave therapy on horses include white hair growth from heat damage to follicles, microfractures on bone surfaces, and a risk of premature growth plate closure in young horses if treatment occurs near growth plates. Improper application or excessively high pressures may increase these risks. Because of potential pain-relief effects, many competition organizations restrict its use within days of an event, so treatment timing requires attention to governing rules.
Summary
- Shockwave therapy applies high pressure soundwaves to tissues causing damage, leading to increased healing and repair
- Many veterinarians use shockwave therapy for treating ligament injuries and arthritis in horses
- There is currently limited scientific evidence to support the efficacy of ESWT in treating lameness conditions
- Some competition organizations have regulations on ESWT use prior to competition
References
- Baxter. G. M., Ed., Adams and Stashak’s lameness in horses, Seventh edition. Hoboken, NJ: Wiley-Blackwell, 2020.
- Boström. A. et al., Systematic Review of Complementary and Alternative Veterinary Medicine in Sport and Companion Animals: Extracorporeal Shockwave Therapy. Animals. 2022. doi: 10.3390/ani12223124.
- Yocom. A. F. and Bass. L. D., Review of the Application and Efficacy of Extracorporeal Shockwave Therapy in Equine Tendon and Ligament Injuries. Equine Veterinary Education. 2019. doi: 10.1111/eve.12780.
- Schlachter. C. and Lewis. C., Electrophysical Therapies for the Equine Athlete. Veterinary Clinics of North America: Equine Practice. 2016. doi: 10.1016/j.cveq.2015.12.011. View Summary
- Da costa Gömez. T. M. et al., Effect of Focused and Radial Extracorporeal Shock Wave Therapy on Equine Bone Microdamage. Veterinary Surgery. 2004. doi: 10.1111/j.1532-950x.2004.040005.x. View Summary
- Bosch. G. et al., Effect of Extracorporeal Shock Wave Therapy on the Biochemical Composition and Metabolic Activity of Tenocytes in Normal Tendinous Structures in Ponies. Equine Veterinary Journal. 2007. doi: 10.2746/042516407X180408. View Summary
- MacKay. A. V. et al., Characterization of the Use of Shock Wave Therapy among Equine Veterinarians. Can Vet J. 2020. View Summary
- Frisbie. D. D. et al., Evaluation of the Effect of Extracorporeal Shock Wave Treatment on Experimentally Induced Osteoarthritis in Middle Carpal Joints of Horses. 2009. View Summary
- Trager. L. R. et al., Extracorporeal Shockwave Therapy Raises Mechanical Nociceptive Threshold in Horses with Thoracolumbar Pain. Equine Veterinary Journal. 2020. doi: 10.1111/evj.13159. View Summary
- Dahlberg. J. A. et al., Force Platform Evaluation of Lameness Severity Following Extracorporeal Shock Wave Therapy in Horses with Unilateral Forelimb Lameness. javma. 2006. doi: 10.2460/javma.229.1.100. View Summary
- Johnson. J. E. et al., Shockwave Therapy for Treatment of a Burn Injury in a Horse. Equine Veterinary Education. 2010. doi: 10.1111/j.2042-3292.2009.00018.x.
