Soft tissue injuries remain one of the most challenging problems in performance horse care. These structures absorb tremendous force every day, and when they fail, the path back to soundness is long, technical, and dependent on understanding how the body rebuilds itself.
Modern veterinary medicine has come a long way in understanding how these structures heal and why some tendons return to strength while others struggle. At the center of that progress is a clearer picture of the three primary phases of tendon healing, how each phase works, and what horses need during each stage.
Success isn’t just about treating the injury. It’s about treating it at the right point in the healing timeline.
Why Tendons and Ligaments Are So Vulnerable
Tendons connect muscle to bone; ligaments connect bone to bone. Both are built from dense, collagen-rich tissue designed to handle the forces of galloping, turning, stopping, jumping, and collection. Some tendons are designed to store and release energy, while others provide stability and precise control of the limb.
These structures constantly absorb impact and cyclic load. Over time, aging, repetitive strain, poor footing, long toes/low heels, or sudden overload can weaken the fibers. A single moment of overload or strain is often just the final straw.
When a tendon is injured, the body responds immediately, but the quality of the healing depends entirely on how the next weeks and months that follow are managed.
The Three Phases of Tendon Healing
Tendon healing is not linear. Each phase overlaps with the next, and every stage demands a different management approach.
1. Acute Phase (Inflammation) — First 1–2 Weeks
When fibers tear, the body triggers a rapid inflammatory response. Blood flow increases, fluid enters the area, and immune cells move in to clear damaged tissue. This is when horses show the classic signs of injury: heat, swelling, and lameness.
Inflammation isn’t necessarily bad, but too much, or inflammation that fails to resolve, leads to dysfunctional repair.
During this period:
- Damaged fibers are removed.
- The body begins preparing the site for repair.
- Both intrinsic tendon cells and extrinsic cells from surrounding tissues contribute to the early response.
Even after the visible swelling subsides, low-grade inflammation can persist, and this ongoing inflammatory activity is strongly associated with long-term reinjury risk.
Management goal:
Support controlled inflammation without shutting down the healing process. Cold therapy, rest, and appropriate veterinary-guided treatments are the main priority during this phase.
2. Subacute Phase (Fibrous Repair) — Weeks to Months
A few days after the injury, the body enters the repair phase. Fibroblasts begin producing fibrous scar tissue to restore mechanical strength to the weakened area. This early tissue is flexible, disorganized, and nowhere near as strong as the original, uninjured collagen structure.
This phase:
- Fills the defect with new tissue
- Establishes early structural strength
- Begins forming a temporary matrix the tendon will later remodel
However, if this phase goes too far or progresses too quickly, scar tissue becomes dense, stiff, and inelastic. That’s when long-term performance is most compromised.
Management goal:
Introduce controlled, progressive loading under veterinary guidance. Early, correct movement helps fibers align and prevents excessive scarring.
3. Chronic Phase (Remodeling) — Months to Over a Year
The chronic phase can extend more than 12–18 months in serious tendon injuries. This is when the temporary repair tissue begins to reorganize. Healthy collagen gradually replaces the repaired collagen, and the tendon slowly regains strength.
But even with ideal management, remodeled tendon tissue never returns to its original elasticity. It becomes stronger, but stiffer, which is why reinjury often occurs next to the original site, where healthy, more elastic fibers stretch against a rigid segment.
During this phase:
- Collagen fibers align along lines of tension
- Cross-sectional area stabilizes
- Echogenicity improves on ultrasound
- Striation patterns begin to resemble normal tendon
Management goal:
Maintain a carefully monitored, ascending exercise plan. Ultrasound should guide increases in workload.
Why Many Chronic Tendon Injuries Struggle to Heal
Once the tendon reaches the chronic stage, many early healing events have already occurred. Excess scar tissue, lingering low-grade inflammation, and poor fiber organization are difficult to reverse.
New research shows that persistent inflammation is one of the biggest drivers of failed healing, especially in older horses. When the body can’t activate natural “resolving” mediators, the tendon remains locked in a cycle of inflammation and fibrosis.
This is where supportive therapies become essential.
How Tendonall Fits Into the Science of Healing
Tendonall is designed to address the biochemical processes that influence tendon repair and long-term tendon health — particularly the relationship between inflammation and fibrosis.
How Tendonall Supports Healing
Tendonall is a highly purified analogue of retinoic acid (RA), a molecule involved in:
- Extracellular matrix formation
- Inflammatory signaling
- Fibrosis regulation
- Collagen metabolism
- Tissue remodeling
RA pathways are complex, and impurities in typical formulations can trigger unwanted effects. Tendonall is synthesized to a strict standard with minimal contamination by other RA isoforms to ensure it targets the pathways beneficial for tendon healing.
In injured tendons, Tendonall may:
- Help modulate inflammatory pathways
- Reduce excessive growth-factor activity associated with fibrosis
- Support healthier collagen organization
- Aid the remodeling process during long-term repair
- Address low-grade, persistent inflammation linked to chronic tendinopathy
How Tendonall Supports Prevention
Even before injury, tendon fibers undergo microstrain. Tendonall’s influence on collagen metabolism and inflammatory signaling helps support:
Soft tissue healing takes time, structure, and a clear understanding of what each phase requires. The more precisely an injury is managed, the stronger and more functional the outcome.
Modern therapies, better imaging, and deeper knowledge of tendon biology have dramatically improved what’s possible. With proper management and science-based support, horses have a stronger chance than ever to return to work soundly.
Understanding the Phases of Soft Tissue Healing in Horses