Effect of sagittal spinal alignment on knee pain in patients with severe knee osteoarthritis: A cross-sectional study

Sagittal spinal alignment is closely related to knee joint function, and sagittal malalignment can affect knee joint pain. This study investigated the association between knee joint pain intensity and sagittal spinal alignment in patients with knee osteoarthritis.

This retrospective study enrolled 187 patients with knee osteoarthritis who were scheduled for primary unilateral total knee arthroplasty (TKA) from December 2021 to March 2023. Patients were assigned to either the Normal or Imbalance group according to the pelvic incidence (PI) minus lumbar lordosis (LL) values. Knee joint function was compared between patients with and without matched sagittal spinal alignment. The primary outcome was patient-reported pain intensity.

A total of 132 patients (22 men and 110 women, mean age: 75 ± 6.7 years [range, 55-89 years], mean body mass index: 25.3 ± 3.8 kg/m²) were evaluated preoperatively. The Imbalance group categorized by PI minus LL values (≥10) comprised 45 patients (34 %, mean age: 76.5 ± 5.9 years, mean body mass index: 25.5 ± 3.3 kg/m²). The mean pain intensity on the affected side was significantly higher in the Imbalance group (P = 0.020). No differences in psychosocial factors were found between the two groups. Knee joint function regarding knee joint extension angle in the standing position was significantly greater in the Imbalance group (P = 0.035).

Sagittal plane malalignment was associated with knee joint pain in patients with knee osteoarthritis who were scheduled for TKA. Our results suggest the need for preoperative pain control interventions that consider the effects of sagittal spinal alignment.