Abstract
PURPOSE: Knee-spine syndrome emphasizes the interplay between knee and spinal alignments. Previous studies have reported that low back pain (LBP) is strongly associated with knee osteoarthritis (OA) pain. Therefore, we investigated how total knee arthroplasty (TKA) influences lumbar alignment and LBP, hypothesizing that LBP improves after TKA in patients without preoperative lumbar deformity. METHODS: We evaluated 87 patients undergoing unilateral primary TKA for knee OA. Lumbar sagittal alignment (C7 sagittal vertical axis (C7-SVA), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL)), knee alignment (hip-knee-ankle angle), range of motion, and clinical outcomes (EQ-5D, Locomo, 2011 Knee Scoring System, Oswestry Disability Index (ODI)) were assessed preoperatively and at three and 12 months postoperatively. Patients were categorized into three clusters based on preoperative lumbar alignment (PI-LL) and changes in ODI. RESULTS: Radiographic changes included a significant increase in C7-SVA and LL, and a decrease in PT. Clinically, ODI and EQ-5D improved significantly at three months, with benefits persisting at one year. The greatest improvement in LBP was observed in a cluster with worse preoperative back pain but without severe lumbar deformity. CONCLUSION: Patients without severe lumbar deformity but with LBP may benefit from TKA, as their LBP may be secondary to knee OA. In contrast, those with severe lumbar deformity may show limited LBP improvement postoperatively.