# The mediating role of sacral slope in the relationship between lumbar lordosis and knee alignment in knee osteoarthritis: an imaging study

## TL;DR

This study shows that the curvature of the lower back (lumbar lordosis) is linked to knee alignment in knee osteoarthritis, with the sacral slope partially explaining this relationship.

## Contribution

The study quantifies the mediating role of the sacral slope in the relationship between lumbar lordosis and knee alignment in knee osteoarthritis.

## Key findings

- Lumbar lordosis was positively correlated with sacral slope and sagittal hip-knee-ankle angle.
- The sacral slope mediated 10.74% of the relationship between lumbar lordosis and knee alignment.
- The study supports a 'spine-pelvis-knee' approach for assessing and treating knee osteoarthritis.

## Abstract

This study aimed to investigate the association between lumbar lordosis (LL) and the sagittal hip-knee-ankle angle (sHKA) in patients with knee osteoarthritis (KOA) and to quantify the mediating effect of the sacral slope (SS).

This study enrolled 507 participants (left-side 302, right-side 205). Lateral full-length X-ray films of the lower extremities in weight-bearing position were collected from the research participants to measure radiological parameters such as lumbar lordosis (LL), sacral slope (SS), and sagittal hip-knee-ankle angle (sHKA), and SF-12 (12-items Short Form Health Survey) and WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) scores were also collected. Correlation analysis and Bootstrap mediation effect analysis were performed.

Among the 507 KOA participants, LL was positively correlated with SS, HKA, sHKA, and SF-12 scores, and negatively correlated with JLCA and WOMAC scores. The mediation analysis revealed that SS accounted for 10.74% of the total association of LL on sHKA.

In patients with KOA, LL is closely related to sHKA, and this statistical association may be partially mediated by SS. This highlights the importance of adopting a “spine-pelvis-knee” perspective when assessing and treating KOA.