Department of Anaesthesia, Royal Free Hospital, London, UK
Lumbar zygapophyseal joints are synovial joints with a fibrous capsule. Each joint has superior and inferior articular processes. The medial branch of the dorsal ramus innervates the joint at the same vertebral level and a level below, except L5, which is the dorsal ramus itself. The nerve passes over the base of the superior articular process to pass under the mammillo-accessory ligament. Prevalence rate of lumbar facet pain is 10–40 %. Risk factors include advanced age, genetic predisposition, hyperlordosis and scoliosis.
It may be due to various arthritis syndromes or due to degenerative changes in the joints. It may be because of microfractures and capsular or cartilaginous tears. Infection may contribute to the pain. Cartilage erosion with sensitisation of subchondral pain with substance P leads to pain. The most commonly affected joints are L4/L5 and L5/S1.
44.2 Clinical Features
Mild to moderate low back pain is seen which is referred to the hip and groin. It can extend beyond the knee and even may be seen in the feet. It is aggravated by twisting and extension of the spine. It gets worse on standing and sitting and is relieved by walking and forward flexion.