Radiographic and clinical risk factors of total knee arthroplasty in asymptomatic knees; a 15-year follow-up study

Background Radiographic signs of osteoarthritis (OA) are frequent in knees without symptoms. The long-term impact of these findings is not completely elucidated.  We wanted to evaluate whether radiographic or clinical baseline findings are associated with the risk of total knee arthroplasty (TKA) in knees without symptomatic OA but with clinical OA of the other knee during a mean follow-up period of 15 years. Methods A follow-up analysis was performed in 100 persons with unilateral, clinical knee OA according to the ACR (American College of Rheumatology) criteria, who participated in a clinical trial between 2000 and 2002. Baseline radiographs of the contralateral, non-symptomatic knee were available in 88 participants at follow-up. Data on TKA procedures were extracted from the Danish National Patient Register at follow-up. Radiographic and clinical findings were analyzed for associations with subsequent TKA. Results At follow-up, 40 % had received a TKA in their non-symptomatic knee. The risk of TKA was significantly associated with baseline joint space narrowing (risk ratio (RR) 1.6 (95% confidence interval (95% CI) 1.4 to 1.9)), osteophytes (RR 1.5 (95% CI 1.3 to 1.8)) and subchondral sclerosis (RR 2.4 (95% CI 1.6 to 3.7)). Among the clinical findings, only baseline body mass index (BMI) was significantly associated with the risk of TKA (RR 1.4 (95% CI 1.1 to 1.8)). Conclusions Radiographic OA changes and BMI at baseline were significantly associated with the long-term risk of TKA in persons without symptomatic knee OA but with symptomatic OA in the contralateral knee, implying that radiographic OA findings are important prognostic factors regardless of symptoms.