Objective: To analyze whether the subcutaneous lumbar spine index (SLSI) is a risk factor for low back pain (LBP) in patients with osteoporotic vertebral compression fractures (OVCF) following percutaneous balloon kyphoplasty (PKP). Methods: A total of 80 OVCF patients were selected. Based on the Visual Analogue Scale (VAS) score 1 month post-PKP, patients were divided into two groups: LBP group (VAS ≥ 4, n = 35) and non-LBP group (VAS 0.05). However, the LBP group had higher VAS and ODI scores than the non-LBP group at 3, 6, and 12 months postoperatively (P < 0.05). Univariate and multivariate logistic regression analyses showed that SLSI was significantly higher in the LBP group compared to the non-LBP group (P < 0.05), indicating it as a risk factor for LBP after PKP. ROC curve analysis indicated that the area under the curve (AUC) for SLSI was 0.769 (95% CI: 0.667–0.871), with a cutoff value of 0.765 determined by the Youden index (sensitivity: 88.6%, specificity: 57.8%). Conclusion: A higher SLSI is associated with LBP following PKP. It is recommended that SLSI assessment be performed prior to PKP in OVCF patients as a potential effective predictor for postoperative LBP.