In a published review of the literature on equine tendinopathies (2004), Roger Smith highlights just how difficult it is to run and publish statistically powerful clinical control trials on tendon injuries, and why anecdotal evidence in the treatment of tendon injuries can create potentially harmful biases.
Smith effectively reviews the treatment approaches available, highlighting what we do know, the flags where evidence is weak, and keeps the biology of tendon healing front and center so that our treatment choices ultimately match the lesions in front of us.
The Limitations of Current Evidence
High re-injury rates in common injuries (e.g., SDFT) and large sample sizes required to detect meaningful differences make adequately powered trials rare. Owners also choose and combine treatments in the real world, confounding clean comparisons. Negative experimental results are often discounted in favor of personal anecdotes, which inflates claims and biases decision-making. Ultimately, we must read the literature with caution, lean on pathophysiology, and use objective outcomes when we can.
“Re-injury rates vary between 40 and 50% for sports horses (Dyson, 2004) and 50–60% for National Hunt racehorses (O’Meara et al., 2010), with up to 90% of flat racehorses not returning to racing after tendon injury (Alzola et al., 2018; Tamura et al., 2018). It is therefore clear that for most equine disciplines, a significant percentage of horses do well, in spite of the treatment given, which leads to unsubstantiated claims for efficacy. Using sufficient statistical power (80%) calculations for group sizes necessary to prove a clinically meaningful reduction in the re-injury rate (such as 50%) for any treatment modality compared with a control group, group sizes of 88 horses or more are necessary.”
Roger KW Smith, 2024
Intra- vs Extrathecal Lesions: Location Changes Everything
Extrathecal injuries occur outside a tendon sheath and include SDFT injuries. These tendons have a relative advantage during healing as the body can access the lesion more readily to remove waste and supply the lesion with healing factors. Lesions tend to heal with a robust fibrosis that restores strength – but at the cost of elasticity. This increase in stiffness creates a re-injury risk at adjacent sites to the original injury.
Our current understanding indicates that persistent, poorly resolved inflammation drives maladaptive scarring or fibrosis. Our treatment goals focus on restoring function by modulating inflammation and progressive loading.
Intrathecal lesions occur within a synovial sheath or a bursa, such as the DDFT within the sheath or navicular bursa. Because these tendons are encapsulated in a tendon sheath, they have a significant disadvantage when it comes to nutrition and waste removal or debridement, reducing their healing capacity and prognosis significantly. Communication of a lesion with the synovial cavity can also induce persistent synovitis, resulting in further pain and inflammatory cascades that lead to further degeneration.
“Thus, the treatment goals for intrathecal tendon injuries should be focused on enhancing debridement, facilitating/inducing repair and combatting the inflammatory effects on the tendon sheath or bursa.”
Roger KW Smith, 2024
Rehab Modalities: Laser, Therapeutic Ultrasound, Shockwave, E-stim, Kinesiotape
Across modalities, high-quality evidence is limited.
Class IV/high-intensity lasers can alter healing biology but not always in clinically helpful ways; therapeutic ultrasound and electrical stimulation lack convincing tendon-outcome data. Use shockwave cautiously: it may offer analgesia for chronic entheseous pain (such as hind limb proximal suspensory injuries) while risking damage if applied to acute tendon/ligament lesions. Modality choices should be conservative, healing-phase-specific, and justified by lesion biology, NOT marketing.
“Additional strategies for modulating repair using physical means include shockwave, electrical stimulation, therapeutic ultrasound and laser. None of these modalities have any substantial evidence for their efficacy and potentially can be damaging. A new generation of therapeutic Class IV lasers is currently popular for the treatment of equine tendinopathies and high intensity laser therapy (HILT) has been shown to exert significant effects on healing tendon, although not all of these effects may be linked to improved healing”
Roger KW Smith, 2024
Cold, Compression, Rest
“The simplest and most cost-effective anti-inflammatory treatment is physical therapy consisting of the application of cold and/or compression”
Roger KW Smith, 2024
During the acute inflammatory phase (1-2 weeks post-injury), rest or activity restriction to prevent further injury, coupled with cold and compression treatment can significantly reduce pain and inflammation in a safe and cost-effective way. Cold water spa systems allow the application of cold with hydrostatic pressure and is likely the most effective application technique.
According to Smith, NSAIDs and systemic corticosteroids may be considered in the first 48 hours following injury in some cases.
External Support Systems
Standard compression bandages help control oedema and provide proprioceptive input, but they offer little true mechanical support to the fetlock under load. When short-term protection is needed in early acute care or transport of specific cases, use devices designed to resist hyperextension, such as articulated fetlock-support boots with non-elastic distal straps, figure-of-eight suspensory straps, or a moulded palmar/plantar splint applied over a thick, even, well-padded bandage. These options can modestly reduce peak fetlock extension at walk/trot and stabilise painful tissues, but they are not a license to progress work sooner.
Controlled Activity: How to Progress, What to Include, When to Hold
Once heat and lameness subside, early controlled exercise can be started: typically 5–10 minutes in-hand walking daily, building gradually across months before introducing trot, then canter. Each increase in gait will significantly increase the forces placed on tendons.
Swimming off-loads distal tendons, which is useful for general conditioning, but less so for tendon loading, while underwater treadmill can modulate load when water depth is adjusted appropriately. Progressions and loading decisions should be ultrasound-led: advancing work when cross-sectional area is stable or has significantly decreased ( <~10% change between scans), and echogenicity and fiber pattern improve. Additional ultrasound techniques such as Doppler imaging can be used to determine whether inflammation is trending down. Ultrasound Tissue Characterization (UTC) allows us to monitor tissue repair objectivity.
If lameness, heat, or swelling occur, the tendon should be re-evaluated and controlled activity regressed or halted.
Biologics and Intralesional Therapies
Growth-factor mixes, platelet rich plasma (PRP) and mesenchymal stem cells (MSCs, including autologous bone marrow, adipose, or allogeneic products) are the most used orthobiologics. Experimental work supports improved matrix organization while clinical data is still growing. Appropriately powered studies suggest bone-marrow–derived, cultured MSCs can halve re-injury rates in racing SDFT cohorts compared with conventional management, with signs of superiority over some adipose preparations. However, heterogeneity of products and protocols significantly complicates comparisons of the data available.
Putting it Together: Phase-based, Lesion-led Care
“Healing takes place through three overlapping phases of initial inflammation, subsequent fibroplasia and then a long and incomplete process of remodelling of the scar tissue”
Roger KW Smith, 2024
- Acute Phase care aims to resolve inflammation and protect structure;
- Reparative Phase focuses on loading the tendon just enough to organise fibres and encourage functional remodelling, with biologic consideration where appropriate;
- Chronic Phase care emphasizes progression without relapse, addressing residual pain where present and focusing on a progressive return to function or sport.
Throughout, personalise the plan with objective monitoring and be explicit with owners about timelines and uncertainty.
“Injuries exhibit considerable variability in severity and healing rates. Therefore, any management protocol should be tailored to the individual patient.”
Roger KW Smith, 2024
Conclusion
Evidence-based treatment in equine tendinopathy is as much about aligning with biology as it is about the head-to-head trials we rarely get. The strongest, most repeatable gains still come from getting the early anti-inflammatory window right, being disciplined about controlled, ultrasound-guided progressive loading, and reserving add-on therapies for the right lesion, at the right time, for the right reason. When we pair that discipline with honest conversations about evidence limits and re-injury risk, we protect horses from overtreatment and set more realistic, durable paths back to work.
References
Roger K. W. Smith, Treatment of tendinopathies, Equine Vet Educ. 2024;36:659–672.
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