OBJECTIVE: To observe the pinching action to the nerve root by the lumbar disc herniation and facet or lamina (ligamentum flavum) and evaluate its clinical meaning. METHODS: Seventy-one patients were divided into 3 groups according to the size of distance between protrusion of nuclear and facet or lamina (ligamentum flavum). The degree of the straight leg raising of the affected side (SLR) and the sagittal index (SI) of lumbar disk herniation were measured and analyzed among them. RESULTS: There was no corelation between the affected degree of SLR and sex, age and SI of patient (P > 0.05). The coefficient between distance group and the affected degree of SLR is-0.878 7 (P < 0.01). CONCLUSION: The degree of the surrounding compression by the protrusion of nuclear and facet or lamina (ligamentum flavum) reflects the injuried severity of the nerve root.