A pain in the neck – a look at equine osteoarthritis

Sports horses, in particular, are required to use their entire body in their athletic pursuits and the neck plays a vital role in movement, balance and signal transfer to the rest of the body. Unfortunately, successfully diagnosing and treating problem areas can be ‘a pain in the neck’.

A horse’s neck is an extremely complex structure comprising of more than a hundred muscles, tendons and ligaments that support and move seven large bony vertebrae extending from the poll to the chest.

They attach to one another at two locations, one between the actual body of the vertebrae, cushioned by the intervertebral disks, and another between bony processes that extend along the vertebral top and sides (the articular facet joints).

The all-important spinal cord is protected as it runs through a canal within the middle of these vertebrae, and functions to relay messages from the brain to the peripheral nerves that supply the rest of the body. Cervical nerves extend from the spinal cord, through openings at the side of each vertebral junction.

The sixth, seventh, and eighth cervical nerves contribute to the brachial plexus, an intersection of all of the nerves that supply the forelimbs. Unfortunately, a lot can go wrong with one or more these important, fragile, structures.

It is generally noted that cervical or neck pain often occurs in middle-aged performance horses and is common in those athletes that must collect themselves or turn quickly (such as dressage horses, eventers, jumpers, polo ponies and racehorses).

In these horses, neck pain can often be due simply to wear and tear causing osteoarthritis in the articular joints between one or more vertebra (the articular facets).

Neck pain will most often present as poor performance or a behaviour change that doesn’t match a horse’s normal personality. Specific signs can include a difficult or poor attitude towards their work, a reduced willingness to extend/flex the neck, holding the neck in a neutral or an extended position and sometimes a willingness to work in one direction but not the other.

There are reports of horses experiencing a sudden reluctance or inability to raise their heads at all, only to have this completely resolve over a period as short as several hours. In such cases, it’s possible a nerve root was being pinched where it exits between the vertebrae, a problem that can reoccur if there is an underlying neck abnormality.

In some severe cases, horses have been known to rear, buck or even bolt when asked to turn or flex the neck in a specific way. Safety of the horse and the rider should remain paramount when dealing with a horse with neck pain due to the unpredictability of a horses response to the pain.

It is important for a vet to collect a thorough history when evaluating a horse for potential neck pain. The vet will want to know:

Any resisting of taking the bit;

Any sudden objecting to having their ears or poll touched;

Any history of a fall or accident or being badly cast in the box;

Have they pulled back abruptly and with force when tied up

Started grazing with a very wide or awkward stance

Next a thorough clinical examination should consist of;

Visual examination of the neck for muscle atrophy (wasting) and asymmetry

Careful palpation of the neck for asymmetry or bony protrusions;

Assessing if there is a repeatable pain response to palpation;

Conducting a neck flexibility test often using treats to fully assess the range of movement in the horses neck

Carrying out a complete lameness and neurologic exam

It should be remembered that approximately 7% of horses with cervical arthritis become ataxic (unco-ordinated/wobbly). Ataxia most commonly occurs when there is some damage to the spinal cord itself.

This is normally because of narrowing of the vertebral canal, instability of the bony vertebrae, or pressure from bone proliferation that can develop as a result of degeneration of the joints (osteoarthritis)

In some cases, neck pain can cause a forelimb lameness that can’t be eliminated with nerve or joint blocking. This may be due to pressure on the nerves that pass through openings in the vertebrae to supply the forelimbs.

Pain originating from the neck can also lead to muscular discomfort, most commonly in the long brachiocephalicus muscle that runs along the lower side of the neck and acts to pull the front legs forward (protraction).

Following these examinations, it will often be necessary to use diagnostic imaging, such as radiography (x-rays), ultrasonography, and/or nuclear scintigraphy (bone scan). One or a combination of these techniques will allow careful imaging of the bony and some of the soft tissue elements of the neck.

However, careful interpretation of these images is important as estimates suggest that as many as 50% of horses have radiographic abnormalities in the articular facets at C6-C7, yet have no sign of clinical problems.

There are a variety of treatments for horses that are diagnosed with neck pain, including:

Non-steroidal anti-inflammatory drug administration (phenylbutazone) to act as a pain killers and anti-inflammatories

Time off or modification in the horse’s workload/change in type of work, either temporary or permanent depending on the diagnosed condition and its severity

Cervical facet injections (accurate placement of anti-inflammatory medication most often corticosteroids injected into the facet joints between the cervical vertebrae) these are typically performed with ultrasound guidance, and can be effective in eliminating neck-related signs for a period of time by reducing inflammation and therefore pain

Mesotherapy (injecting very small volumes of corticosteroids and local anesthetics into the mesodermal tissue just under the skin with the aim of reducing discomfort and improving overall range of motion)

Shock wave therapy (desensitization affect)

Acupuncture – this must be carried out be a trained veterinary surgeon

Chiropractic adjustments – only to be carried out by a trained professional

While many horses with neck pain recover well with treatment, some injuries or ailments are too severe to return a horse to his previous level of performance.

The prognosis and outcome for a horse diagnosed with neck osteoarthritis is very much dependent on the severity and how advanced the changes are in the joints involved and how much associated soft tissue damage/inflammation there is present.