Lumbar degenerative kyphosis is a decrease in lumbar lordosis or flat back syndrome in patients without a history of spinal operation and instrumentation. Lumbar degenerative kyphosis may be classified according to the lumbar and compensatory thoracic curvature or the etiology of the deformity. Spinopelvic parameters including pelvic incidencelumbar lordosis mismatch, sagittal vertical axis, C7 plumb line, pelvic tilt, and sacral slope should be measured during diagnosis. Recently, relative lumbar lordosis and lordosis distribution index have also been introduced, and they should also be taken into consideration. Lumbar degenerative kyphosis is mostly seen in elderly patients with high comorbidity, therefore exercise and physiotherapy should be the first line of treatment. Surgery should be provided for patients with severe sagittal imbalance, persistent pain despite conservative measures, and walking difficulty. The main purpose of surgery is to maintain sagittal balance and optimal lumbar lordosis. Each osteotomy technique provides different correction amounts to provide an ideal sagittal balance.