[Purpose] To investigate the incidence of spinal instability among patients with discogenic low back pain and its various effects with respect to the patients’ age, gender, sports activity, and occupation. [Participants and Methods] We assessed 65 patients diagnosed with discogenic low back pain at our clinic between May 2016 and May 2020. After measuring segmental angulation using plain radiographs, we divided these patients into two groups: (1) instability group with >10° of segmental angulation or >3 mm of sagittal translation and (2) stability group with <10° of segmental angulation and <3 mm of sagittal translation. Patient data such as age, gender, sports activity, and occupation were collected using their medical records. [Results] The incidence of spinal instability was 57% (37 patients) among the patients with discogenic low back pain. No significant differences in age, gender, sports activity, and occupation were identified between the groups. [Conclusion] The incidence of spinal instability accounted for more than half of the total number of patients. Additionally, age, gender, sports activity, and occupation did not affect the incidence of spinal instability. Our results support the importance of rehabilitation, such as stability training for spinal instability, for patients with discogenic low back pain.