「腰椎不穩定」目前被認爲是當腰椎被施以外力時所產生的位移大於正常腰椎的一種現象，且是下背痛及坐骨神經痛的主要原因之一。腰椎的穩定是由椎間盤、關節面、肌肉及周邊韌帶共同維持。而有許多因素會造腰椎的不穩定現象，如肌肉張力不足、某些先天性疾病、機械性的退化、創傷，甚至手術、腫瘤或是感染性疾病等都影響腰椎的穩定度。本篇文章將以臨床醫學、影像學、生物力學及物理治療等各種不同領域對腰椎不穩定的概念加以回顧。

Instability of lumbar spine is the subluxation of lumbar vertebrae when external force is present. It is the main cause of low back pain and sciatica. The stability of lumbar spine is maintained by intervertebra discs, facet joints, muscles and adjacent ligaments. Factors that cause the instability of the lumbar spine include weak muscle tension, genetic disorders, degeneration, trauma and even operation, tumor or infection. This article reviews instability of lumbar spine from different fields including clinical medicine, imaging medicine, biokinetics and physiotherapy.