Osteoarthritis of the Articular Process−Synovial Intervertebral Articulation Complexes in Horses

The articular process–synovial intervertebral articulation complexes of the vertebrae in horses are located dorsal to the vertebral canal, at approximately the 10-o'clock and 2-o'clock positions on transverse section. Each is composed of the caudal articular process of one vertebra, the synovial joint (with articular cartilage, synovial fluid and membrane, and articular capsule) located at the base of the interspinal space, and the cranial articular process of the next vertebra. These joints are commonly referred to as the "facet joints."

Osteoarthritis of these joints has been described through the use of radiography and ultrasonography. Sclerosis, enlargement, periarticular new bone, and narrowing of the joint space are frequently identified. Commonly, two to five joints are affected, usually in the caudal cervical, caudal thoracic, and cranial lumbar region.

Diagnosis of osteoarthritis in a facet joint is based on segmental clinical signs in combination with radiographic or ultrasonographic demonstration of abnormal joint contour due to periarticular osteophytes. Sometimes nuclear scintigraphic uptake in the region is abnormal, aiding diagnosis.

Treatment and management of osteoarthritis in a facet joint include ultrasonographically-guided injections of steroids, shock wave therapy, administration of NSAIDs and muscle relaxants, and rehabilitation and mobilization protocols.