Musculus longissimus dorsi
The longissimus dorsi is the largest epaxial muscle. It originates from the iliac crest, sacrum, and spinous and transverse processes of the lumbar and thoracic vertebrae, and inserts on the transverse and articular processes of more cranial vertebrae and the ribs. Bilateral contraction extends the back and loin; unilateral contraction produces lateral flexion. It stabilizes the vertebral column and transmits propulsive forces from the hindquarters. It is innervated by the dorsal branches of the thoracic and lumbar spinal nerves. The cervical portions (longissimus cervicis, longissimus capitis, and longissimus atlantis) continue the system into the neck and to the atlas or skull. They extend and laterally flex the neck and are important for head carriage and collection. Problems in the longissimus system significantly affect rideability, collection, and impulsion.
Origin: Iliac crest, sacrum, spinous/transverse processes of lumbar and thoracic vertebrae
Insertion: Transverse and articular processes of thoracic and cervical vertebrae; ribs
Action: Extends the back and loin; lateral flexion; stabilizes the vertebral column during locomotion
Innervation: Dorsal branches of thoracic and lumbar spinal nerves
Back pain, including kissing spines and sacroiliac dysfunction, commonly manifests as pain and spasm in the longissimus. It is the muscle most often associated with poor performance, reluctance to engage, or resistance under saddle. Diagnostic approaches include clinical examination, ultrasound, and sometimes scintigraphy.
## Overview Primary back muscle strain is the most common riding-related back problem. Overwork, poor saddle fit, or rider imbalance strains the epaxial muscles. Horses show sensitivity on palpation,
## Overview Saddle fit issues create focal pressure points that cause pain, localized muscle atrophy, white hairs, dry spots in the sweat pattern, and behavioral changes such as cold-backed reactions
## Overview Prolonged back pain leads to visible wasting of the epaxial muscles, creating a gutter alongside the spine and a weak, hollow-backed posture. The horse may be unable to carry a rider comf
Kissing spines, also known as overriding dorsal spinous processes, occur when the bony projections along the top of the horse's spine touch or overlap, causing pain and inflammation. This condition mo
Reluctance to bend, bucking, or poor engagement under saddle can involve the longissimus. Have persistent back issues evaluated rather than assuming simple soreness. Balanced work and correct saddle fit help.
## Overview Primary back muscle strain is the most common riding-related back problem. Overwork, poor saddle fit, or rider imbalance strains the epaxial muscles. Horses show sensitivity on palpation, a hollow back under saddle, resistance to transitions, a short choppy stride, and tail swishing. Movement often improves without a rider. ## Causes Overuse, ill-fitting tack, or asymmetric loading. ## Diagnosis Palpation, observation under saddle, and exclusion of bony pathology. ## Treatment Rest, anti-inflammatories, physiotherapy, saddle-fit correction, and gradual return to work. ## Recovery and Prognosis Good with appropriate management. ## Prevention Correct saddle fit, balanced riding, and progressive conditioning. Signs include: sensitivity along the back; hollowed back under saddle; resistance to transitions; short choppy stride; tail swishing; better without rider
## Overview Saddle fit issues create focal pressure points that cause pain, localized muscle atrophy, white hairs, dry spots in the sweat pattern, and behavioral changes such as cold-backed reactions. Uneven saddle wear is another clue. Correct fitting prevents these problems. ## Causes Saddle that is too narrow, too wide, unbalanced, or incorrectly positioned. ## Diagnosis Visual sweat patterns, palpation, and professional saddle assessment. ## Treatment Reflock, adjust, or replace the saddle. Allow pressure points to heal. ## Recovery and Prognosis Excellent once fit is corrected. ## Prevention Regular professional saddle fitting as the horse’s shape changes. Signs include: dry spots in sweaty saddle patch; white hairs along saddle region; muscle atrophy beside withers; cold-backed behavior; uneven saddle wear
## Overview Prolonged back pain leads to visible wasting of the epaxial muscles, creating a gutter alongside the spine and a weak, hollow-backed posture. The horse may be unable to carry a rider comfortably. Recovery requires resolution of the pain plus targeted rehabilitation. ## What It Indicates Chronic disuse from back pain. ## Diagnosis Visual assessment of topline and identification of the underlying pain source. ## Treatment Treat the primary back problem and institute progressive core-strengthening exercises once the horse is comfortable. ## Recovery and Prognosis Good if the pain is controlled and rehabilitation is consistent. Muscle rebuilds slowly. ## Prevention Early intervention for back pain. Signs include: visible groove alongside the spinous processes; prominent spine; weak hollow-back posture; difficulty carrying a rider
Kissing spines, also known as overriding dorsal spinous processes, occur when the bony projections along the top of the horse's spine touch or overlap, causing pain and inflammation. This condition most commonly affects the thoracolumbar region (T13 to L2) and is seen on radiographs in 30 to 40% of horses, though not all show clinical signs. It is a frequent cause of back pain and poor performance in sport horses. ## What it is The dorsal spinous processes are the upward-pointing bony projections of the vertebrae. In kissing spines, these processes are too close together and impinge on each other during movement, leading to bone remodeling, inflammation of the interspinous ligaments, and pain. The condition is often associated with poor posture, weak core muscles, or conformational factors that increase extension of the back. While many horses have radiographic changes without pain, clinical kissing spines cause significant discomfort, especially under saddle. ## Signs and symptoms - Back pain or sensitivity when pressure is applied along the spine - Dipping away from pressure or hollowing the back under rider - Bucking, rearing, or resistance to collection - Poor performance or unwillingness to go forward - Muscle atrophy along the topline - Reluctance to canter or perform lateral movements - Extreme sensitivity at specific vertebral levels during grooming or saddling - Cross-cantering or difficulty maintaining a consistent gait ## Causes and risk factors Kissing spines develop from a combination of conformational, biomechanical, and management factors. Risk factors include weak abdominal and back muscles, repetitive extension of the spine (common in jumping and dressage), poor saddle fit, and genetic predisposition. Horses with long backs or weak toplines are more susceptible. The condition can also develop secondary to other sources of pain that cause the horse to hollow its back. ## How it is diagnosed Diagnosis combines clinical examination, palpation of the back, and imaging. Radiographs are the primary tool and show the proximity or overlap of the spinous processes. Nuclear scintigraphy (bone scan) can help identify active inflammation. Ultrasound evaluates the interspinous ligaments and soft tissues. Local anesthesia of the affected interspinous spaces is often used to confirm that the kissing spines are the source of pain. ## Treatment and management Treatment options range from conservative to surgical. Conservative management includes physiotherapy, core strengthening exercises, shockwave therapy, mesotherapy, and anti-inflammatory medication. Interspinous ligament injections or corticosteroid injections into affected spaces can provide relief. In refractory cases, surgical options such as interspinous ligament desmotomy or partial resection of the spinous processes are used with good success rates in appropriately selected horses. Saddle fit evaluation and rehabilitation are essential components of long-term management. ## When to call the vet Contact your veterinarian if your horse shows signs of back pain, resistance under saddle, or performance issues that do not resolve with basic management changes. Early diagnosis and a multimodal treatment plan offer the best chance of returning the horse to comfortable work. ## Prevention Prevention focuses on maintaining strong core and back muscles through appropriate conditioning and avoiding repetitive spinal extension without adequate strength. Regular saddle fit checks, good footing, and prompt attention to any signs of back discomfort help reduce risk. Horses with conformational risk factors benefit from proactive core strengthening programs. ## Frequently asked questions **Do all horses with kissing spines on X-rays have pain?** No. Many horses have radiographic changes without clinical signs. Diagnosis requires correlation with clinical findings and response to local anesthesia. **Can kissing spines be cured?** Surgical treatment can provide long-term improvement in many horses. Conservative management can control symptoms but may not eliminate the underlying bony changes. **Is surgery always necessary?** No. Many horses respond well to physiotherapy, injections, and rehabilitation. Surgery is usually reserved for cases that do not improve with conservative treatment. This information is for educational purposes only. Always consult with a licensed veterinarian for diagnosis and treatment of your horse. Signs include: Back pain or sensitivity when pressure is applied along the spine; dipping away from pressure or hollowing the back under rider; bucking, rearing, or resistance to collection; poor performance or unwillingness to go forward; muscle atrophy along the topline; reluctance to canter or perform lateral movements; extreme sensitivity at specific vertebral levels during grooming or saddling; cross-cantering or difficulty maintaining a consistent gait
Back pain, including kissing spines and sacroiliac dysfunction, commonly manifests as pain and spasm in the longissimus. It is the muscle most often associated with poor performance, reluctance to engage, or resistance under saddle. Diagnostic approaches include clinical examination, ultrasound, and sometimes scintigraphy.
Reluctance to bend, bucking, or poor engagement under saddle can involve the longissimus. Have persistent back issues evaluated rather than assuming simple soreness. Balanced work and correct saddle fit help.
See the Longissimus Dorsi on our interactive 3D horse model. Open 3D Model