Box 1.

Pathology Recognised As A Component Of Degenerative Lumbosacral Stenosis In Dogs (modified from Worth et al 2009)

Hypertrophy of the ligaments stabilizing the LS junction (dorsal longitudinal ligament ventrally and ligamentum flavum dorsally) Degeneration of the lumbosacral disc, with protrusion of the disc annulus Degenerative joint disease of the articular processes, with modification of the shape of the articular surface, peri-articular new bone formation, and hypertrophy of the joint capsule Lateral spondylosis deformans at the lumbosacral junction and sacroiliac joint which can impinge into the exit zone of the L7-S1 intervertebral foramen, and compress the L7 intervertebral neurovascular bundle Dynamic compression of the cauda equina caused by ventral displacement of the sacrum in relation to L7 (step lesion = retrolisthesis) Dynamic narrowing of the L7-S1 lateral intervertebral foramen during extension of the lumbosacral joint (telescoping) Congenital stenosis of the vertebral canal at the LS junction Transitional vertebral anomaly Osteochondrosis-like lesion of L7 or S1