Os sacrum (pars cranialis)
The sacrum is formed by the fusion of five sacral vertebrae into a rigid triangular bone. It connects the spine to the pelvis via the sacroiliac joints. The cranial segment (first 2-3 sacral vertebrae) forms the sacral wings (alae) that articulate with the iliac wings. The promontory (cranial edge of S1) forms the lumbosacral angle. The caudal segment (last 2-3 sacral vertebrae) tapers and articulates with the first caudal vertebra. The sacral canal contains the cauda equina nerve roots. The sacral foramina transmit the sacral spinal nerves that contribute to the pudendal and caudal rectal nerves. The sacrum transmits hindlimb thrust to the vertebral column and anchors the pelvis.
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Transmits hindlimb thrust to the vertebral column via the sacroiliac joint; anchors the pelvis
Sacroiliac joint dysfunction, sacral fractures, and cauda equina syndrome can affect function. The sacral spinal cord segments give rise to the nerves of the hindlimb and pelvic organs. Trauma to the sacrum or sacroiliac region can cause significant neurologic or locomotor deficits.
Sacroiliac joint disease involves pain and dysfunction in the joint where the sacrum meets the pelvis. It is one of the most common causes of poor hindlimb impulsion and performance problems in sport
## Overview Sacral fracture is a break through the body of the sacrum, usually from falling or rearing backward. It frequently damages the sacral nerve roots, producing acute severe hind-limb weaknes
Sudden hindlimb weakness, incontinence, or abnormal tail tone after trauma should be evaluated immediately.
Sacroiliac joint disease involves pain and dysfunction in the joint where the sacrum meets the pelvis. It is one of the most common causes of poor hindlimb impulsion and performance problems in sport horses. The condition can result from strain, subluxation, or osteoarthritis of the sacroiliac joint and its supporting ligaments. ## What it is The sacroiliac joints are low-motion synovial joints that transfer propulsive forces from the hindlimbs to the axial skeleton. Strong ligaments surround the joints and provide stability. Dysfunction can arise from acute trauma, repetitive stress, poor conformation, or degenerative changes. The joint is difficult to image directly, so diagnosis often relies on clinical signs, response to diagnostic analgesia, and exclusion of other causes of hindlimb lameness. ## Signs and symptoms - Poor hindlimb impulsion and engagement - Hunter's bump (prominent tuber sacrale on one or both sides) - Asymmetric gluteal muscle development - Difficulty with collection, lateral work, or jumping - Pain on palpation or manipulation of the sacroiliac region - Cross-cantering or reluctance to canter on one lead - Chronic cases may show muscle atrophy or compensatory back pain ## Causes and risk factors Sacroiliac joint disease is often associated with repetitive stress in sport horses, conformational issues (especially asymmetry), poor saddle fit, and previous trauma. Young horses in intense training and horses with weak core muscles appear to be at higher risk. The condition can also develop secondary to other sources of pain that alter gait mechanics. ## How it is diagnosed Diagnosis is challenging and usually involves a combination of clinical examination, palpation, and diagnostic analgesia (blocking the sacroiliac region). Radiographs and ultrasound have limited value for the joint itself but can rule out other problems. Nuclear scintigraphy (bone scan) is often helpful for identifying increased uptake in the sacroiliac region. A positive response to local anesthesia in the sacroiliac area supports the diagnosis. ## Treatment and management Treatment typically includes a period of rest or modified exercise, physiotherapy and core strengthening, shockwave therapy, and anti-inflammatory medication. Some horses benefit from sacroiliac joint injections (corticosteroids or regenerative therapies). Long-term management focuses on improving core strength, correcting any saddle fit issues, and addressing conformational or biomechanical contributors. Many horses can return to previous levels of work with appropriate management. ## When to call the vet Contact your veterinarian if your horse shows persistent poor impulsion, asymmetric muscle development, or resistance to collection that does not improve with basic training adjustments. Early intervention often leads to better outcomes. ## Prevention Prevention focuses on maintaining good core strength and symmetry through appropriate conditioning, ensuring proper saddle fit, and avoiding sudden increases in workload. Regular assessment of young horses in training can help identify issues early. ## Frequently asked questions **Is sacroiliac joint disease the same as kissing spines?** No, but the two conditions can occur together and both cause back pain and poor performance. **Can a horse with sacroiliac joint disease still compete?** Many horses return to successful competition with proper management, though some require ongoing treatment and modified training. **How long does recovery take?** Recovery timelines vary. Some horses improve significantly within weeks of targeted treatment, while others require months of rehabilitation. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse. Signs include: Poor hindlimb impulsion and engagement; hunter's bump (prominent tuber sacrale on one or both sides); asymmetric gluteal muscle development; difficulty with collection, lateral work, or jumping; pain on palpation or manipulation of the sacroiliac region; cross-cantering or reluctance to canter on one lead; chronic cases may show muscle atrophy or compensatory back pain
## Overview Sacral fracture is a break through the body of the sacrum, usually from falling or rearing backward. It frequently damages the sacral nerve roots, producing acute severe hind-limb weakness or paralysis, tail paralysis, and urinary and fecal incontinence. Many horses are unable to rise. The injury is often catastrophic. ## Causes High-energy trauma to the hindquarters, especially falling backward. ## Diagnosis Clinical neurologic signs and radiographs or advanced imaging when feasible. ## Treatment Supportive care only. Most horses with significant neurologic deficits are euthanized. Mild cases may be rested. ## Recovery and Prognosis Poor to grave when nerve roots are damaged. ## Prevention Safe handling to reduce rearing and falling risks. Signs include: acute severe hind-limb weakness or paralysis; tail paralysis; urinary and fecal incontinence; inability to rise
Sacroiliac joint dysfunction, sacral fractures, and cauda equina syndrome can affect function. The sacral spinal cord segments give rise to the nerves of the hindlimb and pelvic organs. Trauma to the sacrum or sacroiliac region can cause significant neurologic or locomotor deficits.
Sudden hindlimb weakness, incontinence, or abnormal tail tone after trauma should be evaluated immediately.
See the Sacrum (Cranial Segment) on our interactive 3D horse model. Open 3D Model