To investigate the risk factors of suboptimal postoperative outcomes after short-segment surgery for degenerative lumbar spinal stenosis (DLSS) and severe sagittal imbalance and to recommend the appropriate candidates for the short fusion.A total of 101 elderly subjects underwent short-segment surgery were included. Preoperative sagittal vertical axis decreased to ≤50mm was determined as sagittal compensation, otherwise was determined as sagittal decompensation. At the latest follow-up, 64 patients with sagittal decompensation and 14 patients with proximal junctional kyphosis (PJK) were detected. Sagittal imbalance with the related symptoms was named as symptomatic sagittal imbalance. Preoperative clinical data and spinopelvic parameters were collected and compared between different groups.Symptomatic sagittal imbalance and severe degeneration of paravertebral muscle were revealed to be the risk factor of sagittal decompensation and PJK. More sagittal decompensations (100%) and PJKs (60%) were observed in patients with both of the above risk factors. On the contrary, the postoperative outcomes were superior with less sagittal decompensations (46.9%) and PJK (0%) in those with neither of the two factors.Symptomatic sagittal imbalance and severe degeneration of paraspinal muscle are the risk factors predisposing suboptimal surgical outcomes after lumbar short-segment decompression and fusion for DLSS. We believe essential spinal function and substantial quality of paraspinal muscle are the keys to long-lasting good outcomes.Copyright © 2022. Published by Elsevier Inc.