Ankylosing spondylitis impact on knee cartilage thickness: correlation with demographic data and clinical characteristics

Abstract

Abstract Background Ankylosing spondylitis (AS) is a progressive inflammatory disease involving cartilaginous structures in the spine and peripheral joints. However, the number of the studies assessing knee cartilage thickness in AS and its correlations with parameters of disease activity/severity is even less. We aimed to assess the impact of AS on knee cartilage thickness using musculoskeletal ultrasound (MSUS) and magnetic resonance imaging (MRI). Methods Twenty-five AS patients and 25 healthy individuals (15 served for MSUS assessment, and 10 served for MRI assessment) were included. By employing MRI “using a 1.5-T machine” and MSUS “with a 10–18-MHz linear probe,” respectively, the thickness of the femorotibial cartilage and femoral cartilage was assessed. Results Compared to healthy controls, AS patients showed statistically significantly thinner cartilage thickness (P < 0.05) at all femorotibial cartilage subdivisions and the medial femoral condyle and intercondylar area on both sides. Femoral cartilage thickness measurements either assessed by MSUS or MRI were negatively correlated with age, measures of disease activity, and Bath Ankylosing Spondylitis Radiology Index for the spine (BASRI-s) (P < 0.05). However, MRI tibial cartilage thickness was negatively correlated with disease duration and measures of spinal mobility, functional limitation, and BASRI-s (P < 0.05). MRI total cartilage thickness measurements at the femoral condyle were negatively correlated with Bath Ankylosing Spondylitis Functional Index (BASFI) and Ankylosing Spondylitis Disease Activity Score-erythrocyte sedimentation rate (ASDAS ESR) (P = 0.04 and P = 0.03, respectively). A positive correlation was found between MSUS and MRI total femoral cartilage thickness (P = 0.02). Conclusions The knee cartilage thickness of AS patients was thinner than that of healthy controls. The correlations between cartilage thickness and patient variables demonstrate MSUS and MRI's utility in identifying knee cartilage loss areas in AS patients.