Summary

In patients with radiographic knee OA, knee pain was associated with low back pain and lower thoracic kyphosis. These patients before knee operation keep their standing posture with decreasing thoracic kyphosis, when pelvic retroversion and anterior shift of the C7 plumb line occur with aging.

Abstract

Introduction

There are many patients who have severe radiographic knee osteoarthritis (OA) without pain. On the other hand, knee joints are influenced by spinal alignment to keep the standing and walking postures. It is still unknown how much the extent of the knee pain in the radiographic knee OA patients is associated with spinal alignment. We investigated the relationship between the knee pain in the radiographic knee OA patients and sagittal spinal alignment using the data of volunteers aged over 50.

Methods

We reviewed questionnaires and radiographs of 217 subjects in musculoskeletal examination for the volunteers with age over 50. Utilizing the antero-posterior radiographs of the whole lower extremities in standing position, knee osteoarthritic grade (Kellgren-Lawrence grading system (KL grade)) and alignment of lower extremities (hip-knee-ankle angle (HKA)) were evaluated. From these 217 subjects, 101 subjects (31 males, 70 females and the average 76 years) with radiographic knee OA above KL grade 2 were selected for this study. Then, we divided the subjects into two groups (knee pain group (Group P: 60 subjects) and no knee pain group (Group N: 41 subjects)) by the respondent of questionnaires. Utilizing the lateral radiographs of whole spine and pelvis obtained during neutral standing, we evaluated thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), spinal sagittal global alignment (sagittal vertical axis (SVA: the horizontal distance between C7 plumb line and sacrum)) and femoral inclination angle (FIA: the angle formed by plumb line and line between hip center and femoral proximal shaft). We compared the presence of low back pain and these radiographic parameters between both groups.

Result:
The average of each measurements values were as follows: In Group P, age: 75 years, number of subjects with low back pain: 42 (70%), TK: 31°, LL: 39°, PT: 24°, SVA: 23mm, FIA: 10°and HKA: 185°. In Group N, age: 77 years, number of subjects with low back pain: 15 (37%), TK: 38°, LL: 40°, PT: 23°, SVA: 35mm, FIA: 11°and HKA: 184°. Group P showed significantly higher low back pain and lower thoracic kyphosis (p < 0.01), suggesting that spinal malalignment and condition may associated with knee pain in the radiographic OA patients.

Conclusion

In patients with radiographic knee OA, knee pain was associated with low back pain and lower thoracic kyphosis. These patients before knee operation keep their standing posture with decreasing thoracic kyphosis, when pelvic retroversion and anterior shift of the C7 plumb line occur with aging.