Understanding the Pain Cycle in Horses - Part 1: When Pain Persists After Healing

When a horse is injured, nerves in the affected area send pain signals to the brain. Under normal circumstances, those signals quiet down once the tissue heals. But in some horses, the nervous system does not reset as expected. Instead, the pain pathways remain overactive—a process known as peripheral sensitization.

What Is Peripheral Sensitization?

When tissue is injured, the body releases inflammatory chemicals such as histamine and prostaglandins to support healing. While necessary, these substances also lower the activation threshold of nearby nerves. Over time, those nerves begin firing with less and less stimulation.

As a result, sensations that were previously neutral—light touch, grooming, normal movement—can start to feel uncomfortable or painful.

Subtle changes in posture, muscle tone, and sensitivity often signal the early stages of pain, even before clear lameness or visible injury is present.

What This Can Look Like in Horses

Early signs are often subtle and easily misinterpreted:

• Flinching or twitching during grooming

• Tight, hollow posture or a braced neck

• Sensitivity to tack that was previously well tolerated

• New or escalating behavior changes under saddle

Pain leads to muscle tension, tension increases inflammation, inflammation further sensitizes nerves—and the cycle continues.

Why Early Recognition Matters

When identified early, peripheral sensitization is often reversible. Addressing the physical drivers, improving comfort, and reducing ongoing irritation can help reset the system before pain becomes chronic.