Lameness can be the result of a problem involving any or all of the legs, the back and the neck. Early recognition and diagnosis of a lameness problem are the critical points in being able to develop an effective treatment plan to get the condition resolved and your horse back to normal. Continuing to ask your horse to perform when he is lame could actually worsen the condition and result in failure of the horse to make a complete recovery.
Lameness is obvious if it is severe and results in a limb bearing little or no weight. However, lameness can also be subtle, and it may be difficult to detect the precise location within the limb or limbs from which it originates. In some cases, lameness may be due to a soft tissue or skin injury and not involve the musculoskeletal system. For example, a deep laceration over the horse's shoulder could result in the horse favouring that limb. Also, be aware that an area that is painful during movement may result in your horse feeling unbalanced as you ride him, or result in an actual change in his behaviour. Pain in his back or neck could cause your horse to be unwilling to perform a task, such as a gait change or lead change that it would otherwise have done.
In a forelimb lameness, the head and neck tend to rise when the lame leg is bearing weight or hits the ground, and fall when the sound leg hits the ground.
In a hindlimb lameness, the hip or pelvis "hikes up" when the lame leg is weight bearing or contacts the ground, and moves downward when the sound limb hits the ground.
Diagnosing the lame leg becomes more difficult when the horse has more than one limb affected or a combination of limb and neck and/or back or other areas.
The Lameness Examination
Your veterinarian will conduct a lameness examination that consists of several parts. At all times, there will be close observation of the horse while it is moving as well as standing still and at rest. Additionally, the veterinarian will use his/her hands to feel ("palpate") the animal to detect any signs of heat, swelling and/or pain. The lameness will be graded. Many veterinarians make use of a grading scheme recommended by the American Association of Equine Practitioners (AAEP).* Grading can be used to determine if a horse is responding to treatment, – has the grade of lameness improved? Using a standardized scheme also makes discussions between a veterinarian and specialist (such as a surgeon) about a specific patient, more accurate and meaningful.
|0||Lameness not perceptible under any circumstances.|
|1||Lameness is difficult to observe and is not consistently apparent, regardless of circumstances (e.g. under saddle, circling, inclines, hard surface, etc.)|
|2||Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances (e.g. weight-carrying, circling, inclines, hard surface, etc.)|
|3||Lameness is consistently observable at a trot under all circumstances|
|4||Lameness is obvious at a walk|
|5||Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move|
- The veterinarian will watch the horse walk in a straight line as well as circled on both soft and hard surfaces. The walk is a useful gait to evaluate because, at a slower gait, it may be easier to detect slight changes from what would be considered normal. Different surfaces can be useful because some forms of lameness may be more accentuated on a hard surface than a soft one, and the reverse also is true. On a hard surface, the veterinarian can also listen to the sound of the hooves contacting the ground. The lame leg usually contacts the ground with less force and this difference can sometimes be heard.
- Watch the horse trot in a straight line as well as a circle, on both soft and hard surfaces. The trot is a useful gait to evaluate because it consists of a two-beat stride pattern, and the horse's weight is distributed evenly between diagonal pairs of legs.
- Sometimes the horse will be asked to canter or lope. This can be useful for detecting problems in certain areas such as lower back.
- In some cases, the veterinarian may ask you to saddle and ride the horse, while he/she continues to evaluate the gait. Moving the horse up and down an incline can also be a useful aid to detect some types of lameness.
Flexion tests may be performed, which consist of flexing a joint or joints and holding it in flexed position before asking the horse to move off again in walk and trot. This evaluates the range of motion and the response to flexion: after the area has been flexed, does it increase the degree of lameness? Performing this type of test can help localize the site of lameness.
Other tools to help localize the site of lameness include:
- Hoof testers are used to apply pressure on specific areas of the hoof to detect a response, which is usually related to pain in the area.
- Nerve blocks: Your veterinarian may need to inject local anaesthetic at various points along the leg/foot to temporarily ‘numb' a nerve, or into a joint. The horse is trotted again and the response to the block evaluated. Various nerves can be sequentially blocked and the observation process repeated. The veterinarian is watching for the horse to "go sound" when the nerve block has been successful and in this way, identify the site or region of lameness.
Further diagnostic tests may be indicated such as radiographs and ultrasound examination. Radiographs give more information regarding the underlying bone while ultrasound examination helps to assess soft tissues like tendons.
More specialized techniques such as MRI (magnetic resonance imaging) thermography (determination of surface heat to detect superficial inflammation), nuclear scintigraphy and computerized axial tomography (CAT scan) may be recommended in some cases. These types of procedures are often performed at only a few clinics or veterinary schools.