A closer look: Lameness in Horses
Lameness is extremely common in horses, with estimates suggesting that approximately 5% of horses are lame on any given day. Lameness is a very non-specific symptom, and can indicate a wide array of potential underlying conditions that range from mild to severe. Thorough work-up by a veterinarian is the only way to identify the cause of lameness.
Some causes of lameness are emergencies. Lameness that develops suddenly, or lameness where a horse is non-weight bearing on a limb requires immediate veterinary attention.
There are many causes of lameness in horses, ranging from mild to severe. These conditions can affect virtually any component of the musculoskeletal system, including injuries and conditions of the bone, joints, hoof, tendons, muscle, and occasionally the skin. Broad causes of lameness include pain, mechanical restrictions on normal stance or gait, or neuromuscular disease.
The severity of lameness is graded on a 4 point scale, with 0 being no lameness and 4 being complete lack of weight bearing on a limb. The severity of lameness is not always correlated with the prognosis or severity of the underlying condition.
In general, sudden lameness occurs from more severe conditions. Many of these conditions have a poor prognosis, depending on their severity. Examples include:
- Bone fractures
- Joint infections
- Traumatic injuries to the tendons
- Acute laminitis
Lameness that develops slowly over time is generally associated with manageable conditions with a favorable prognosis, such as:
- Caudal heel pain syndrome
- Tendon or ligament inflammation
- Joint capsule inflammation
Testing and diagnosis
Diagnosis of the underlying cause of lameness is extremely challenging, due to the wide variety of causes. The first step in diagnosis is isolating the location of the underlying issue. Diagnostic tests include:
- Standing physical examination
- Examining the horse in motion
- Flexion tests, where the joints are hyperflexed to test for soreness
- Hoof tester examination of all feet
- Regional anesthesia, where nerves to certain locations are numbed to reduce pain
Through these tests, a location that is the most likely source of lameness is identified. Diagnostic testing then focuses on determining the underlying cause. Tests include:
- Diagnostic imaging, including X-rays and ultrasound
- Specialized imaging, such as MRI, CT scan, or bone scan
- Arthroscopic examination of a joint
Treatment depends on the underlying cause found, and can vary widely between cases. Commonly used treatments include:
- Injections into the joint spaces
- Anti-inflammatory medications
- Massage therapy
- Specialized medications to target particular conditions
“Rein lameness” can be mistaken for true lameness. In this condition, a gait irregularity is only seen when the horse is ridden, and the source of the irregularity is the horse resisting the rider’s aids. Distinguishing rein lameness from true lameness is difficult.
An irregular gait is also a symptom of ataxia, where horses move in an irregular fashion due to a neurological deficit or injury. Distinguishing ataxia from lameness involves a thorough veterinary exam.
Signs of lameness can be subtle, particularly if the lameness is mild.
Signs of lameness include:
- Head bobbing at the trot
- “Hip hike” at the trot when viewed from behind
- Dragging the hooves
- Tracking up unevenly
- Frequent stumbling or tripping
- Unwillingness to put pressure on a limb