Temporal changes in synovitis and chronic pain after total knee arthroplasty: A two-year longitudinal study

Chronic post-surgical pain (CPSP) following total knee arthroplasty (TKA) leads to significant patient dissatisfaction post-operatively. Previous cross-sectional research has identified post-TKA synovitis as a key factor influencing CPSP, but there is a lack of longitudinal data. This study aimed to analyze risk factors for post-TKA pain and synovitis, including pre-operative elements, to better understand their roles in CPSP. A cohort of 49 knees from 42 patients undergoing TKA for osteoarthritis was assessed. Demographic data, pre-operative and post-operative radiographic findings, pre-operative magnetic resonance imaging, intra-operative blood loss, and post-operative C-reactive protein levels were documented. Chronic pain, measured using the WOMAC pain subscale, and synovitis, quantified by our original “total PD score” using power Doppler (PD) ultrasonography, were recorded pre-operatively and at six months, one year, and two years post-operatively. Multivariable analysis was used to identify factors contributing to chronic pain and synovitis at these time points. Multivariable analysis showed that the total PD score was significantly associated with chronic pain at one and two years post-TKA. Pre-operative WOMAC pain subscale scores were also significantly associated with chronic pain at one year. For synovitis, the pre-operative total PD score was associated at the two year mark, and body mass index (BMI) was found to be a contributing factor at six months, one year, and two years. Greater overall synovitis on PD ultrasonography was significantly associated with chronic pain post-TKA. Greater pre-operative synovitis and lower BMI were identified as contributing factors to post-TKA synovitis on PD ultrasonography. Further research is warranted to explore additional unassessed factors influencing post-TKA synovitis and to enhance imaging assessments. • Synovitis peaks at six months after total knee arthroplasty (TKA), then declines at one and two years. • Chronic pain correlates with synovitis at one and two years, but not at six months post-TKA. • Lower BMI and higher pre-operative synovitis are risk factors for post-TKA synovitis.