How Vets Use Nerve Blocks to Find Lameness in Horses

When a horse becomes lame, identifying exactly where the pain is coming from is not always straightforward.

Many structures within the limb can produce similar clinical signs, making it difficult to determine the source of discomfort from gait assessment alone. A horse may present with an obvious lameness, or simply feel uneven, resistant, or inconsistent under saddle.

After the initial process of identifying the lame limb, the next stop is to localise where in that leg the lameness is coming from. Diagnostic nerve blocks in horses are considered one of the most valuable tools in a lameness investigation.

By temporarily numbing specific regions of the leg and reassessing movement, veterinarians can systematically identify where pain is originating and guide further diagnostic imaging.

What Is a Diagnostic Nerve Block?

A diagnostic nerve block involves placing a small amount of local anaesthetic around a specific nerve or within a joint. Typically we start low down on the limb and then work our way up the leg. By doing this, we can indentify clearer which structures we are blocking. If we put the block in too high, there are too many

structures below the nerve block. By numbing or taking away sensation from too many structures at once, if the horse improves, we won’t know which structure was causing the initial discomfort.

As such we work our way systematically up the limb, so we can do our best to be clear on which structures we are desnensitising.

If the lameness improves significantly after the block, this indicates that the source of discomfort is likely located within the area that has been desensitised. This helps ensure that further imaging and treatment are directed toward the most relevant area. In many cases, they provide the missing piece of information needed to reach an accurate diagnosis.

How Does a Nerve Block Examination Work?

After the horse's gait has been assessed and a region of interest identified, local anaesthetic is placed around the nerves or into a joint.

The horse is then reassessed after the anaesthetic has had time to take effect.

Post block, we evaluate:

• degree of improvement

• changes in gait symmetry

• stride length

• willingness to move forward

• response during circles or specific movements

Significant improvement following a block helps determine whether the source of discomfort lies within the desensitised region.

Why Imaging Alone Doesn't Always Provide the Answer

One of the most common misconceptions is that x-rays or ultrasound should always be performed first.

However, many horses, particularly older performance horses, will have abnormalities visible on imaging that are not necessarily causing pain.

Radiographs may reveal arthritic changes, remodelling, or other findings that are incidental and

unrelated to the current lameness.

For this reason, imaging is often most valuable after the painful region has been localised through gait assessment and diagnostic nerve blocks. This helps ensure that findings are interpreted in the correct clinical context and that treatment decisions are based on the structures contributing to the lameness.

Can Objective Gait Analysis Be Used With Nerve Blocks?

Yes.

Objective gait analysis can be particularly useful during nerve block investigations.

By measuring gait symmetry before and after a block, veterinarians can objectively assess changes in movement and quantify improvement. In particular, using objective gait analysis, takes away any bias we have as vets and owners following a block, ensuring that a horse is wither truely improved or not. We classify an improvement, if there is at least a 50% positive change.

The addition of objective analysis is especially valuable in:

• subtle lameness cases

• hind limb lameness

• multilimb lameness

• compensation patterns

• performance horses with low-grade asymmetry

Objective gait analysis does not replace clinical examination but provides additional information alongside veterinary assessment.

Are Nerve Blocks Safe?

Diagnostic nerve blocks are routinely performed during equine lameness investigations and are generally well tolerated. As with any veterinary procedure, there are potential risks, including infection, local irritation, or inadvertent desensitisation of adjacent structures. These risks are minimised through appropriate preparation and technique.

What Happens After a Nerve Block?

Once the painful region has been localised, further diagnostics may be recommended.

This may include:

• radiography (x-ray)

• ultrasound

• advanced imaging where indicated

Identifying the affected region allows treatment and rehabilitation plans to be tailored to the individual horse and condition.

FAQ’s

Why would my vet recommend nerve blocks for lameness?

Diagnostic nerve blocks help identify the region responsible for pain when the source of lameness is not immediately obvious. By temporarily numbing specific areas of the limb, veterinarians can systematically localise discomfort and guide further diagnostics.

Do nerve blocks tell you the exact structure that is injured?

Only when the joint is directly blocked and improves quickly (5mins), while regional blocks numb out a larger area, helping rather localise lameness to a region. More specific nerve blocks can be performed at a later date, or diagnostic imaging can be performed to identify the specific structure(s) involved.

Does a positive nerve block mean surgery is required?

No. A positive nerve block simply indicates that the source of discomfort is located within the desensitised region. Treatment recommendations depend on the underlying diagnosis.

Can nerve blocks be used in subtle lameness cases?

Yes. Nerve blocks are often particularly valuable in horses with subtle or complex lameness where the source of discomfort is not immediately obvious.

Why might several nerve blocks be required?

The limb is assessed systematically. Multiple blocks may be performed to progressively narrow down the region responsible for the lameness.

Are nerve blocks painful for horses?

In general nerve blocks can be well tolerated, however there may be slight stinging feeling as the anaesthetic is going in. For more challenging nerve blocks, some horses may require a nose twitch, which helps keep the horse still, and improves compliance particularly with horses that may kick. Our goal is always to make the experience as positive as possible, using treats and positive reinforcement where possible, whilst also keeping our team safe.

Final Thoughts

Diagnostic nerve blocks are one of the most important tools available during a lameness investigation.

By helping localise the source of discomfort, they allow veterinarians to target imaging more effectively, improve diagnostic accuracy, and develop an appropriate treatment and rehabilitation plan.

When combined with clinical examination, gait assessment, objective gait analysis, and diagnostic imaging, nerve blocks play a critical role in identifying the cause of lameness and helping horses return to comfortable performance.

Want to learn more about how we work up lameness? Click here