Disorders of the back include fractures, muscle and ligament strain, degenerative diseases, kissing spines syndrome, and injuries to the sacroiliac junction (the joint between the back and pelvis).
Multiple fractures in the upper portions of the vertebrae of the withers are sometimes seen in young horses that have reared up and fallen over backward. After the initial pain and local reaction have subsided, the horse usually recovers with no permanent effect on performance. A persistent swelling over the withers, however, may require use of a special saddle. Occasionally, other spinal fractures occur, and their presence can be confirmed with x-rays. The signs in these cases are variable.
Fractures of the main body of the vertebrae are more serious. Such fractures usually result from a bad fall entailing a somersault. Damage to the spinal cord may cause complete or partial paralysis of the limbs. The outlook for recovery is grave.
Muscle and Ligament Strain
Damage to the soft tissues is the most common cause of back soreness in the horse. This mostly involves the group of muscles along the back. Usually, all or parts of these muscles are strained while the horse is being ridden. The principal sites of damage are located just in front of and behind the saddle area. Signs include alteration of the horse's performance and acute back pain. Most of these injuries respond to rest and physiotherapy, although several weeks may be needed for full recovery (see Bone, Joint, and Muscle Disorders in Horses: Muscle Disorders in Horses).
Another fairly common site of soft-tissue damage is the ligament that runs down the middle of the back. Signs of damage to this ligament typically persist longer, and the chances of complete recovery are not as good as for the uncomplicated muscle strains.
There is considerable controversy over the diagnosis and treatment of back problems in horses. Much credit is given to the value of physiotherapy, particularly chiropractic and osteopathic manipulation, but there is often little to substantiate their effectiveness.
Degenerative Diseases of the Spine
Degenerative diseases of the spine in the thoracic region (chest area of the back) are uncommon in working horses. However, when they are seen, they have serious effects, and little can be done to keep the horse working.
Arthritis with the degenerative loss of cartilage of the joints of the lumbar vertebrae (rear area of the back) is much more common, especially in older horses. Lumbar arthritis, however, appears to cause little inconvenience to the horse because this part of the spine is kept particularly rigid even when the horse is jumping.
Kissing Spine Syndrome
The spinous processes are the bony structures that protrude upwards from the vertebrae. You can feel their upper points in the midline of the back between the large back muscles. They do not normally touch each other; however, with kissing spines syndrome, 2 or more do. This may be partially due to the effects of bearing a rider. When this occurs beneath the saddle area, some horses develop back pain. The condition may also cause a local bone reaction, small bone cysts, and false joint formation. Diagnosis can be aided by injection of local anesthetic into the affected spaces between the spinous processes. Many cases respond to rest and physiotherapy, but persistent cases may require surgically removing one or more of the tops of the spinous processes to relieve the crowding of the spines.
Sacroiliac Injury (Dislocation, Strain, Arthrosis, Hunter's Bumps)
Acute and severe strain of the sacroiliac ligaments typically results from an injury. It can produce severe pain in the pelvic or sacroiliac region and lameness in the hindlimbs. Longterm sacroiliac strain is a cause of back soreness. It may indicate incomplete healing or reinjury of an earlier strain. Sacroiliac injury may affect a horse's performance, producing intermittent, often shifting, hindlimb lameness. The action of the hindlimbs may be reduced, and the horse may drag the toe of one or both hooves.
Sacroiliac injury is common in Standardbreds and hunter-jumper horses. It is sometimes confused with longterm stifle problems. Usually, the quarters muscles will be poorly developed and, when viewed from behind, the hindquarters may be asymmetrical. This may be due to some tilting or rotation of the pelvis or muscle wastage of one quarter, or both. In the early stages of injury, pressure applied to the area may cause pain. The horse may hold its tail slightly to the side and be reluctant to bend its back. If a diagnosis is made early and the horse is rested long enough to allow complete healing of the damaged ligaments (6 to 9 months), recovery can occur. However, Standardbreds usually do not compete well following a sacroiliac injury. Horses with lasting injuries continue to perform poorly despite rest and anti-inflammatory medication.
Last full review/revision July 2011 by Russell R. Hanson, DVM, DACVS, DACVECC; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS; Andrew P. Bathe, MA, VetMB, DACVS, DEO, MRCVS; Leo B. Jeffcott, MA, BVM, PhD, FRCVS, DVSc, VD; Svend E. Kold, DMV, MRCVS, RCVS Specialist in Equine Surgery (Orthopedics); C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS; Dale A. Moore, MS, DVM, MPVM, PhD; Sheldon Padgett, DVM, MS, DACVS; Tracy A. Turner, DVM, MS, DACVS, DABT; Stephanie J. Valberg, DVM, PhD, DACVIM; John F. Van Vleet, DVM, PhD