General

Lameness

Lameness is one of the commonest problems that horse owners consult their vets about. Diagnosing the cause can be a difficult, time consuming and frustrating task. Blue Cross Hilda Archer Centre Vet Richard Stephenson discusses the common causes of lameness concentrating on foot problems.

How can I tell if my horse is lame?

Most lameness is detected when the horse is trotting. This is because at the trot the horse is in ‘two time’ movement which is usually symmetrical. If a horse is lame in a fore limb at the trot it will move its head slightly away from the lame leg and downwards towards the sound one when it is taking weight on it. The hind limbs are slightly more difficult to assess. What you need to remember is that the hip of the lame leg will move up and down more than the hip of the sound leg. If a horse is equally lame in both fore limbs it can be extremely difficult to identify that there is a problem at all. Often there may be non – specific signs such as refusing to jump, shortened stride, change of temperament or uneven shoe wear.

How is lameness diagnosed?

Most lameness examinations begin by carefully feeling the suspect limb to detect any lumps or ‘heat’. Vets will usually look at the general conformation of the limb as this can help give us some clues as to what is making the horse lame.

This horse is ‘pigeon toed’ – poor conformation can contribute to lameness.
After the initial examination of the horse at rest your vet will need to make a ‘dynamic’ assessment of the horse’s movement. Generally most vets like to see the horse walked away and back and will then ask for the horse to be trotted up. The trot up is a critical part of each lameness investigation and vets frequently grade the severity of the problem on a scale of 1 – 10. On the 10 point scale a horse that is unable to take weight on its limb would be rated 10 / 10ths lame and a sound horse 0 / 10ths lame. A very slight lameness is 1 – 2 /10ths a moderate lameness 4 / 10ths and anything above 5 / 10ths indicates that a severe lameness is present.

Following the first trot up ‘flexion’ tests on the suspect limb can be used to help localise the cause of lameness. Flexion tests are particularly helpful in testing for degenerative joint disease (arthritis), whilst they give a useful indication of where a problem might lie they are not particularly accurate and should not be used on their own to make a diagnosis.

Having made a general assessment your vet will begin a thorough systematic examination of the affected limb. As foot problems are the commonest source of lameness this phase of the investigation invariably starts at the bottom of the leg.

Hoof testers are systematically applied around the circumference of the hoof and sole to see if pain can be detected.

Where hoof testers fail to give any clues the vet can ‘nerve block’ the foot. This is a process by which local anaesthetic is injected into the nerves supplying the foot to temporarily desensitise it. If there is a foot problem present a nerve block will make the horse sound.

Where a foot block fails to affect the horse’s gait then your vet will begin to work his way up the limb blocking the nerves at different sites in an attempt to localise the problem to a specific joint or structure. Sometimes the joints can be injected with local anaesthetic such as the fetlock or knee if there is a suspicion that the lameness is caused by a problem within them. Thus by using a combination of limb palpation, careful observation, nerve and joint blocks veterinary surgeons can usually localise the cause of lameness.

The next stage is to ‘image’ the suspect area. There are two main imagining modalities used by vets, radiography and ultrasound. X – Rays are very good for looking at bones but give little information about the ‘soft tissues’ such as tendons. Over the last five years there has been a revolution in the world of radiography with digital systems replacing the old X – Ray films. Digital X – Rays have enabled high quality radiographs to be obtained of horses with small portable X – Ray machines. Modern ultrasound machines enable the tendons and ligaments to be imaged, again in recent years digital technology has resulted in a tremendous improvement in the quality of ultrasound images.

More recently a new technique ‘magnetic resonance imaging’ (MRI), has started to become widely available – particularly for examining the horse’s foot. This is enabling vets to unravel some of the mysteries of well know, but previously poorly understood lamenesses such as ‘navicular’ disease. Currently MRI scans are relatively expensive but as the technology develops and more veterinary clinics have the equipment they will become increasingly accessible.

What are the common causes of lameness?

There is an old adage ‘no foot – no horse’. This emphasises the fact that the vast majority of lameness cases relate to the horse’s foot. In fact a foot abscess is the commonest cause of lameness. They can result in severe pain but are readily treatable if detected at an early stage. Other common foot problems include laminitis, arthritis of the joints within the foot, ‘navicular disease’, fractures and tendon or ligament strains.

The foot abscess.

Signs.
It cannot be over emphasised that most sudden onset lamenesses in the horse are caused by foot abscesses. Often the animal will be severely lame – sometimes 10 / 10ths. Sometimes the pain is so severe that the horse will lie down or have difficulty standing. Many horses will sweat or even appeal to have colic due to the level of discomfort. There will be heat in the affected hoof, and a bounding digital pulse. Hoof testers are very useful in locating the problem but not infallible. Sometimes there will be oedematous swelling extending up the leg to the lower third of the tendons.

Diagnosis.
Usually the combination of signs and the severity of the lameness are sufficient for your vet to make a diagnosis. Unfortunately not every case is that simple so sometimes it is necessary to nerve block the foot and take X – rays.

Treatment.
There are no short cuts. The abscess must be found and drained. Antibiotics will not cure a foot abscess and should be avoided until good drainage has been made. Tetanus is a real risk after a foot abscess so always check that your horse’s vaccinations are fully up to date.

Laminitis

Signs.
Laminitis remains one of the most commonly encountered lamenesses. Can be of very sudden onset called ‘acute’ laminitis. There is invariably a bounding pulse to both fore feet. The horse is reluctant to move and will often try to bring its back legs underneath its body to take more weight on them. It can progress to ‘chronic’ (long term) laminitis. Chronic laminitics have a stiff gait, landing heel first with an increased stride length.

Diagnosis.
Usually the clinical signs are sufficient for experienced equine vets to be able to make a diagnosis. Most vets try to avoid using nerve blocks in laminitis investigation as they might encourage increased weight bearing on the feet. X – rays are very helpful in managing the condition but are rarely needed to make a diagnosis.

Treatment.
Just because laminitis is common does not mean that it is not serious. This is NOT something that any responsible horse owner should try to treat themselves. Always call your vet. The main components of successful treatment for ‘acute’ laminitis are strict rest, strict dietary management, adequate support to the feet, pain relief and control of blood pressure.

Arthritis.

Signs.
Can be unilateral or bilateral but normally one limb is more badly affected than the other. Is often of gradual onset and in the initial phase of variable severity. Arthritis (now called degenerative joint disease) is progressive.

Diagnosis.
Will need to be ‘localised’ by using nerve blocks and palpation. Often arthritic joints are strongly positive to flexion tests. Ultimately the diagnosis is supported by the use of radiographs.

Treatment.
At one time other than using anti inflammatory drugs there was little could be done for degenerative joint disease. We now have a range of products that can help protect cartilage and restore function to joints provided the disease is caught early in its course. Vets routinely use drugs like hyaluronic acid (artificial joint fluid) and ‘IRAP’ to support damaged joints.

Navicular disease.

Signs.
This is a bilateral FORE limb lameness. It can be very insidious in onset. Initially the horse may simply be reluctant to jump or may have a reduced stride length. Owners often feel that there is something wrong but are unable to specific what. As the disease progresses the signs become more obvious and as one limb is often worse than the other overt lameness can be detected.

Diagnosis.
Usually navicular disease is diagnosed by a combination of nerve blocking at the palmar digital level and X – Rays. The advent of MRI has revealed that many horses previously thought to have the disease are affected by other lesions such as damage to the deep digital flexor tendon or the collateral ligaments of the coffin joint. Modern vets favour the term navicular syndrome to encompass these varying pathologies.

Treatment.
Most treatments for ‘navicular syndrome’ are based on correcting any foot imbalance, shoeing with plenty of support to the heel area, and improving blood flow to the foot. Where MRI has shown specific ligament damage shock wave therapy can be used.

How to help your vet diagnose your horse’s lameness.

Finding out why a horse is lame is essential to prescribing the correct treatment. Unfortunately it can be very difficult and time consuming in some cases to reach a diagnosis. It requires team work between you and your vet and a great deal of patience. The owner has a vital role to play in assisting the vet find the answer.

Do

  • Make sure your horse has regular foot care. You don’t have to have shoes but you do need regular attention to the feet by a qualified farrier.
  • If you suspect lameness call your vet at an early stage.
  • Be prepared to give an accurate history of the problem to your vet. He / she will want to know how long the horse has been lame, if the lameness is associated with any particular incident e.g. a kick, if there has been a previous problem and if you have detected any heat or swelling.
  • Keep your horse’s TETANUS vaccinations up to date – foot abscesses are a common cause of tetanus.

Don’t

  • Give any form of pain killer e.g. phenylbutazone BEFORE your vet has seen the horse and certainly not prior to a lameness examination. Generally your vet needs to be able to see the lameness if he / she is to be able to make a diagnosis – giving ‘bute’ prior to an examination is a sure way to prevent your vet finding out what is wrong – and it is surprising how many people do this!
  • Try to make a diagnosis yourself.
  • Continue to work a lame horse – unless you have been advised that it is necessary for its treatment.
  • If your horse is normally shod don’t remove the shoes prior to a lameness examination.

Basic ‘nerve blocks’.

‘If only they could talk’ – horses would be able to tell us where their legs hurt. Unfortunately it’s not that simple! However by blocking the sensory nerve to the painful area the horse will become sound and thus by observing a change in gait before and after a ‘nerve block’ vets can tell which area of the leg is painful.

Fortunately almost all lameness problems are in the lower limb. Below the knee and hock there are no muscles in the horse so all the nerves are ‘sensory’. By knowing the location of the nerves and the areas that they supply vets can pin point the cause of the problem.

The two most common nerve blocks are the used to numb the back third of the foot and the whole foot.

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