Extracorporeal shockwave therapy (ESWT) is a non-invasive therapy used most frequently to treat soft tissue injuries. In this therapy, a high-energy soundwave is produced outside of the body (hence the therapy is referred to as being extracorporeal) and transmitted into the target tissue. The effect of the high-energy soundwave is to stimulate the growth of new blood vessels and trigger a series of cellular reactions that ultimately result in tissue healing.
Some of the science behind exactly how ESWT helps the healing process is still being looked into, but there are plenty of studies confirming that the therapy reduces swelling and reorganises collagen, which is necessary for the healing of a ligament, as ligaments are made of collagen. Interestingly, ESWT has been shown to be particularly effective at healing enthesopathies, which are injuries to a ligament at its attachment to the bone. Shockwave therapy is also recognised as an effective management tool for bone pain. It is commonly used to manage degenerative joint diseases such as arthritis: to address causes of back pain like kissing spine; and to assist in the healing process of stress fractures.
The therapy can also be of benefit in chronic or old injuries when the healing process has slowed down or stopped. In these cases the application of the shockwaves can help revitalise or restart the healing response by stimulating the body’s local inflammatory response.
ESWT has few side effects and can be performed in the stable. However, the treatment itself can be a bit painful and the noise that that machine makes can upset some horses, so most horses require light sedation prior to treatment.
ESWT is therefore a fairly standard recommendation from a vet as an additional treatment option in a situation such as yours. ESWT is not sufficient as a stand-alone therapy, but as you say in your note, your vet is also providing additional modalities of treatment.
ESWT as part of a treatment plan is believed to be a very helpful and beneficial addition.