Equine Lordosis (Swayback): Understanding Causes, Symptoms, Diagnosis, and Management

What is lordosis in horses?

Lordosis in horses, commonly known as "swayback" or "hollow back," is a spinal conformational anomaly characterized by an excessive downward curvature of the thoracolumbar region of the vertebral column, resulting in a pronounced dip in the horse's back.

Understanding Equine Spinal Anatomy

To comprehend lordosis, it's essential to first understand the normal structure of the equine spine. The horse's vertebral column is a complex, segmented structure providing support, flexibility, and protection for the spinal cord. It comprises five main regions:

• Cervical (neck): 7 vertebrae
• Thoracic (chest): Typically 18 vertebrae, characterized by prominent dorsal spinous processes to which the ribs attach.
• Lumbar (loin): Typically 6 vertebrae, designed for stability and power transmission.
• Sacral (pelvis): 5 fused vertebrae forming the sacrum.
• Caudal (tail): 18-22 vertebrae.

Lordosis specifically affects the thoracolumbar region, the area where the thoracic and lumbar vertebrae meet and extend through the loin. In a healthy horse, this region should exhibit a slight, gentle arch upwards or be relatively flat, providing a strong, flexible bridge between the forequarters and hindquarters. The integrity of this region relies heavily on the vertebrae, strong ligaments, and the powerful epaxial (dorsal) and hypaxial (ventral) musculature that supports and stabilizes the spine.

Defining Lordosis

Lordosis, or "swayback," is a permanent conformational defect where the thoracolumbar spine sags excessively downwards, creating a noticeable concavity in the horse's back. This deviation from the normal spinal alignment can range from subtle to severe. In severe cases, the dorsal spinous processes of the vertebrae may become highly prominent, and the horse's abdomen may appear to drop significantly.

Biochemically, lordosis places abnormal stress on the intervertebral joints, ligaments, and muscles of the back. The ligaments along the dorsal aspect of the spine (supraspinous and interspinous ligaments) become stretched, while the ventral ligaments may shorten. The epaxial muscles, which normally work to extend and stabilize the spine, become overstretched and weakened, contributing to the "hollowed" appearance and reduced support.

Causes and Contributing Factors

Lordosis is a multifactorial condition, meaning it can arise from a combination of genetic, age-related, and management factors:

• Genetic Predisposition: This is a primary cause. Lordosis is heritable and commonly observed in certain breeds, such as American Saddlebreds, Tennessee Walking Horses, and Arabians, suggesting a genetic component affecting collagen and connective tissue integrity.
• Age-Related Degeneration: As horses age, the ligaments supporting the spine can naturally lose elasticity and strength (ligament laxity), and muscle tone may decrease. This allows the spine to sag over time, particularly in older broodmares due to the stretching effect of multiple pregnancies.
• Weak Core Musculature: Insufficient development or atrophy of the core abdominal and back muscles (epaxial and hypaxial muscles) can lead to inadequate support for the vertebral column, allowing it to sag.
• Poor Conformation: Horses with inherently weak backs, long backs, or poor angulation of the hindquarters may be predisposed.
• Nutritional Deficiencies: While less common as a sole cause in adult horses, chronic malnutrition or mineral deficiencies during growth can impair bone and connective tissue development.
• Improper Training or Workload: While not a direct cause of structural lordosis, poor riding practices (e.g., constantly riding with the horse hollowed out, lack of engagement of the hindquarters, ill-fitting tack) can exacerbate an existing predisposition or worsen the condition by weakening supporting musculature.
• Mares with Multiple Pregnancies: The significant weight and abdominal distension during multiple pregnancies can stretch the abdominal muscles and ventral ligaments, contributing to a dropped back appearance.

Clinical Signs and Impact on Performance

The signs of lordosis vary depending on its severity, but often include:

• Visible Spinal Sagging: The most obvious sign is a distinct dip in the horse's back, often most pronounced behind the saddle area.
• Prominent Dorsal Spinous Processes: The bony projections of the vertebrae along the topline may become more visible and feel sharper to the touch.
• Difficulty with Saddle Fit: Saddles may "bridge" (contact only at the front and rear, leaving a gap in the middle), leading to uneven pressure, rubs, and discomfort for the horse. This can cause behavioral issues under saddle.
• Muscle Atrophy: The epaxial muscles along the spine may appear underdeveloped or wasted, particularly lateral to the spinous processes.
• Pain and Stiffness: Horses may exhibit back pain, sensitivity to touch or palpation along the spine, reluctance to be saddled, or resistance to bending.
• Gait Abnormalities: Shortened strides, reduced impulsion from the hindquarters, unwillingness to engage the back, or a "hollow" way of going can be observed.
• Reduced Athletic Performance: Lordosis can limit a horse's ability to collect, use its back effectively, jump, or perform demanding athletic tasks due to pain or mechanical restriction.
• Secondary Conditions: The altered biomechanics can predispose horses to other back problems, such as kissing spines (overriding or impinging dorsal spinous processes) due to compensatory spinal compression.

Diagnosis of Lordosis

Diagnosis typically involves a multi-faceted approach by an experienced veterinarian or equine professional:

• Visual Assessment: A thorough conformational analysis from multiple angles (side, front, rear) to evaluate the spinal alignment and overall body structure.
• Palpation: Gently feeling along the spine to identify areas of pain, muscle tension, atrophy, or abnormal prominence of bony structures.
• Dynamic Examination: Observing the horse in motion at various gaits, in hand, on the lunge, and under saddle (if applicable) to assess range of motion, lameness, and how the back is used.
• Radiography (X-rays): Can confirm the degree of vertebral angulation and identify any associated bony changes, such as osteoarthritis in the facet joints or impinging dorsal spinous processes (kissing spines).
• Ultrasound: May be used to assess the condition of soft tissues, such as ligaments and muscles, and to rule out other causes of back pain.

Management and Prognosis

While structural lordosis is a permanent conformational change and cannot be "cured," its symptoms and impact on the horse's welfare and performance can often be managed effectively.

• Veterinary Consultation: Essential for accurate diagnosis, ruling out other causes of back pain, and developing a tailored management plan.
• Correct Saddle Fit: This is paramount. An ill-fitting saddle will exacerbate pain and muscle atrophy. Custom-fitted saddles or specialized pads designed for swayback horses are often necessary to distribute weight evenly and avoid pressure points.
• Targeted Exercise Program: Focus on strengthening the core muscles (abdominal and back muscles) to provide better support for the spine.
  • Ground Exercises: Carrot stretches (encouraging the horse to reach between its front legs or towards its flanks to lift its back), belly lifts (gentle pressure under the belly to encourage abdominal contraction).
  • Riding Exercises: Long and low work to encourage stretching and engagement of the topline. Incorporating poles and cavaletti can help activate core muscles and improve back flexibility. Avoid exercises that encourage hollowing of the back.
• Physical Therapy and Bodywork: Modalities such as chiropractic adjustments, acupuncture, massage therapy, and therapeutic ultrasound can help alleviate pain, improve muscle function, and enhance flexibility.
• Weight Management: Maintaining an ideal body weight reduces the load and strain on the horse's back.
• Pain Management: Non-steroidal anti-inflammatory drugs (NSAIDs) or other medications may be prescribed by a veterinarian for acute pain episodes or chronic discomfort.
• Prognosis: The prognosis for horses with lordosis varies widely. Mild cases may live a full, comfortable life and even compete successfully with appropriate management. Severe cases, particularly those with associated pain or secondary conditions like kissing spines, may have a limited athletic career and require ongoing, intensive management to maintain comfort and quality of life.

Differentiating from Other Conditions

It's important to distinguish lordosis from other conditions that might affect the horse's back:

• Kyphosis (Roach Back): This is the opposite condition, characterized by an excessive upward curvature of the spine, giving the back a rounded or "roached" appearance.
• Malnutrition or Emaciation: A very thin horse may have prominent spinous processes due to lack of muscle and fat cover, giving the appearance of a hollow back. However, true lordosis is a structural skeletal deviation, not simply a lack of soft tissue.
• Kissing Spines (Overriding Dorsal Spinous Processes): While often associated with lordosis due to altered spinal mechanics, kissing spines is a distinct condition where the spinous processes touch or impinge upon each other, causing pain. Lordosis can predispose a horse to kissing spines.

Conclusion

Lordosis, or swayback, is a significant conformational characteristic in horses that can impact their comfort, performance, and overall well-being. While often genetically influenced and exacerbated by age, understanding its causes and implementing proactive management strategies are crucial. A comprehensive approach involving veterinary care, appropriate saddle fit, targeted exercise, and supportive therapies can help horses with lordosis lead comfortable and productive lives, emphasizing the importance of informed horsemanship and a commitment to equine health.