Symptoms predict total knee arthroplasty more than osteoarthritis severity: A multivariable analysis of more than 7500 knees

Purpose: Multiple clinical factors may concur to determine the clinical trajectory leading towards total knee arthroplasty (TKA) in patients affected by knee osteoarthritis (OA). The aim of this study was to identify the main factors influencing progression to TKA in a large population of knee OA patients. Methods: A total of 7552 knees were selected from the Osteoarthritis Initiative (OAI) multicentre database. The data collected included demographic data, Kellgren–Lawrence (KL) grade, the presence of knee swelling, the frequency of swelling, visual analogue scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and the number of knees requiring TKA. The baseline data were collected as reported by the OAI database, and patients were followed up at 12, 24, 36, 48, 60, 72, 84 and 96 months, documenting whether they underwent TKA during this period. Results: A multivariable analysis was performed to identify factors independently influencing progression to TKA. At 96 months, 7.1% of knees underwent TKA. The progression to TKA correlated with age (p < 0.001), KL grade (p < 0.001), swelling frequency (p < 0.001), knee swelling (p < 0.001), VAS (p = 0.003) and KOOS (p < 0.001). Knees with KL Grades 3 and 4 had the same risk of undergoing this procedure, while the need for TKA was able to be predicted based on WOMAC pain (p = 0.035, hazard ratio [HR] = 0.864), VAS (p = 0.008, HR = 1.131) and KOOS (p = 0.02, HR = 0.966). Conclusions: This study revealed that several factors influenced progression to TKA, including age, KL grade, knee swelling, VAS pain and KOOS. However, there was no statistically significant difference between KL 3 and KL 4 in predicting the disease trajectory, and patients' clinical symptoms, as quantified by WOMAC pain subscale, VAS and KOOS, had a greater influence on progression to TKA than knee KL OA severity. Level of Evidence: Level IIb.