Class IV laser therapy offers veterinarians an option for pain relief and tissue healing in patients. | Courtesy Dr. Niklas DrummWhen a horse sustains a soft-tissue injury or struggles with chronic musculoskeletal pain, rehabilitation can feel like a long road back to soundness. In recent years Class IV laser therapy has become an increasingly valuable tool for veterinarians and equine rehabilitation professionals, offering new options for pain relief and tissue healing.Class IV lasers use targeted light energy to stimulate healing, reduce inflammation, and relieve pain. Compared to lower-level cold lasers, Class IV devices deliver significantly more power, enabling deeper penetration and a broader range of therapeutic effects.These devices have an output power greater than 500 milliwatts, compared to less than 500 milliwatts from Class III devices, says Mathilde Pluim, PhD, a faculty member at Ghent University, in Belgium. That higher energy allows the light to reach deeper tissueslike tendons and ligamentswhere it can have a measurable impact on healing.Researchers have shown that lower-level lasers transmit only about 1.81.9% of light energy into equine tendon tissue at an 800-nanometer wavelength, which is too little for effective tendon treatment, says Pluim. High-power lasers deliver enough energy to produce changes in deeper structures, she adds.How to Use Class IV Lasers for Equine RehabilitationClass IV laser therapy has become a key component of many equine rehabilitation programs. Martha Rodgers, VMD, owner of Shephard Hill Equine, in Lexington, Kentucky, uses hers most often to treat tendon and ligament injuries, acute trauma, and musculoskeletal pain, as well as pain in large muscle groups. I also use my Class IV for wound healing and to stimulate acupuncture points in extremely needle-phobic horses, she says.Equine veterinarians incorporate Class IV laser therapy into a structured rehab plan to support other modalities such as controlled exercise, physiotherapy, and extracorporeal shock wave therapy. In clinical studies Pluim says horses with superficial and deep digital flexor tendon or suspensory ligament lesions treated with Class IV lasers experienced:Reduced lameness and better ultrasound healing scores within two weeks.Return to exercise in approximately six weeks.Full return to previous performance within six months.Lower reinjury rates (1721%) compared with traditional conservative treatments (4244%).These results show that laser therapy doesnt replace a rehabilitation programit enhances it, says Pluim. By supporting better tissue quality and reducing inflammation, the horse can move comfortably through each stage of recovery.The Science Behind Class IV LasersAt the cellular level laser therapy works through photostimulation, or light-induced activation of mitochondria (the cells energy centers). Laser energy is absorbed by cytochromes and chromophores on cell membranes and within mitochondria, explains Rodgers. That leads to mitochondrial activation, nitric oxide formation, and improved cell signaling.These changes lead to beneficial effects, including:Pain relief from increased serotonin and beta-endorphins, vasodilation from nitric oxide release, and improved oxygen deliveryReduced inflammation due to boosted ATP production and nitric oxide levels, with decreased inflammatory mediators such as interleukin-1 and prostaglandinsTissue repair caused by increased macrophage activity, fibroblast proliferation, and collagen formation, plus greater neovascularization and enhanced growth factor activity.In her research Pluim also found measurable improvements at the tissue level, including smaller lesion size, improved collagen alignment, and enhanced fiber strength. These changes translate into stronger, more functional repair tissuecritical in reducing reinjury risk once the horse returns to work, she says.Developing a Class IV Laser Treatment Plan for HorsesLaser therapy protocols vary depending on the horses condition, injury location, and stage of healing. In acute cases, such as the first 48 hours after injury, we may treat daily or every other day, Rodgers says. For chronic issues, one or two sessions per week are typical, with frequency decreasing as healing progresses.Dosage depends on target tissue depth and type. Rodgers recommends:15 joules/cm for superficial tissues.820 joules/cm for general musculoskeletal applications.Up to 30 joules/cm for deep muscle or tendon structures.Most horses respond well to 812 joules/cm for common rehabilitation needs, she says.In Pluims experimental work, she and colleagues used a 15-watt continuous-wave laser emitting four wavelengths (635, 660, 810, and 980 nanometers), delivering approximately 250 joules per cubic centimeter (an accurate unit of measure when treating deeper tissues) of treated tissue. She adds that available literature shows significant variation in dosages used but the dosages she studied had positive effects on the treated horses.Correct technique is essential for safety and efficacy, Pluim says. Shaving and cleaning the skin improves penetration, she explains. The handpiece should be kept in motion and held perpendicular to the tissue to avoid overheating and energy loss.Because Class IV lasers generate warmth, Rodgers adds that the veterinarian should monitor both tissue temperature and the horses comfort throughout treatment. Class IV sessions are nonpainful and usually well tolerated, she says. If heat sensitivity arises, adjusting settings, time, or probe distance quickly resolves it.Safety and Contraindications for Class IV Lasers in HorsesClass IV lasers can serve as powerful therapeutic tools but demand careful handling. Proper control of the treatment environment and protective eyewear are required, Rodgers says. She does not recommend practitioners use it over tumors or on a horses thyroid gland, in pregnant uteruses or epileptic patients, or over pacemakers or other implanted devices, adding that the beam should never be aimed near the eye. Use caution near growth plates in young horses and in treating horses with autoimmune or photosensitive conditions, she says.Horses generally tolerate laser sessions well, Rodgers says. The key is having a calm, attentive handler who keeps the horse still and comfortable.Training and Equipment for Class IV LasersBecause of the power these devices deliver, practitioners must undergo specialized training. Class IV lasersespecially continuous-wave modelsmust be used by someone who understands laser physics, anatomy, and safe operating protocols, says Rodgers.Manufacturers typically provide training upon purchase of a unit. This helps veterinarians learn proper settings for different tissue types, safe beam angles, and signs of overheating. Each company offers either on-site or remote instruction, Rodgers says. Its critical to maximize results and prevent tissue damage.Investment varies, but most Class IV laser systems range from $15,000 to $25,000, says Rodgers, which she views as an investment in long-term patient outcomes. When used correctly, Ive seen faster, stronger healing and lower reinjury rates, especially in tendon and ligament cases.Setting Realistic Expectations for Treatment ResultsWhile Class IV laser therapy can accelerate healing responses, Rodgers cautions against assuming it will shorten the total rehabilitation period. One of our main goals is to produce stronger, more physiologically normal repair tissue, she explains. That takes time and patience.Rather than speeding the clock, laser therapys value lies in improving tissue quality, enhancing comfort, and reducing the risk of reinjury, making it a powerful adjunct to carefully managed rest and progressive conditioning.Take-Home MessageClass IV laser therapy is helping reshape how veterinarians approach equine rehabilitation. Veterinarians are finding that by reaching deeper tissues, enhancing cellular repair, and reducing inflammation, these high-powered devices give injured horses a better chance at returning to full athletic function.High-power laser therapy has shown enhanced healing, reduced lesion size, and better collagen alignment, says Pluim. Lower-level lasers simply lack the power to achieve those outcomes in deep equine structures.