Anatomical Axis on X-Ray and Its Relationship With Pain and Kinesiophobia in Knee Osteoarthritis

Overview

Knee osteoarthritis is a common joint disease that causes pain, stiffness, and limitations in daily activities, especially in older adults. Changes in the alignment of the lower limb, called the anatomical axis, can increase the mechanical load on the knee joint and may affect pain and mobility. This study aims to investigate the relationship between the anatomical axis measured on knee X-rays and patients' pain levels, functional status, quality of life, and fear of movement (kinesiophobia). This is a single-center, observational, cross-sectional study. Adult patients diagnosed with knee osteoarthritis who have a standard knee X-ray taken within the last 6 months and who volunteer to participate will be included. Pain will be measured with the Visual Analog Scale (VAS), functional status with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), quality of life with the 36-Item Short Form Health Survey (SF-36), and kinesiophobia with the Tampa Scale for Kinesiophobia (TSK). The femoro-tibial angle and joint space width will be measured on X-rays by two independent observers. By examining the relationship between radiographic alignment and clinical findings, this study may provide new insights into the comprehensive evaluation of knee osteoarthritis and help guide treatment planning for patients.

Knee osteoarthritis (OA) is a prevalent degenerative joint disease that leads to pain, disability, and reduced quality of life, particularly in older adults. Alterations in lower limb alignment, specifically deviations of the anatomical (mechanical) axis such as varus or valgus deformities, play a key role in the development and progression of OA by altering joint load distribution. Varus alignment is commonly associated with medial compartment OA, whereas valgus alignment is related to lateral compartment OA. Previous studies have reported that such malalignment may accelerate structural damage, increase pain, and contribute to functional impairment. In addition to structural changes, chronic pain in OA patients can lead to fear of movement, known as kinesiophobia, which further limits physical activity and negatively affects functional outcomes. However, there are limited studies that simultaneously evaluate the relationship between radiographic alignment, pain, functional capacity, quality of life, and kinesiophobia. This single-center, observational, cross-sectional study will be conducted at the outpatient Physical Medicine and Rehabilitation clinics of Istanbul Physical Medicine and Rehabilitation Training and Research Hospital. The target sample size is 100 patients with knee OA, based on a priori power analysis. Eligible participants must have an anteroposterior knee X-ray taken within the last six months. Pain intensity will be assessed with the Visual Analog Scale (VAS), functional status with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), quality of life with the Short Form-36 (SF-36), and kinesiophobia with the Tampa Scale for Kinesiophobia (TSK). Radiographic measurements, including femoro-tibial angle and joint space width, will be performed by two independent observers using standardized procedures. Collected data will be analyzed using appropriate statistical methods. The findings are expected to provide a more comprehensive understanding of the relationship between anatomical axis alignment and clinical outcomes in knee OA. This may contribute to more effective treatment planning and patient management.