LONGITUDINAL JOINT SPACE WIDTH MEASURES AND RISK OF KNEE REPLACEMENT IN PATIENTS WITH SYMPTOMATIC AND RADIOGRAPHIC KNEE OSTEOARTHRITIS: DATA FROM OSTEOARTHRITIS INITIATIVE.

INTRODUCTION: Although previous studies have shown that baseline joint space width (JSW) and its short-term change are associated with knee replacement (KR) in patients with knee osteoarthritis (OA), it remains unclear whether the longitudinal trajectory of JSW is associated with KR risk. OBJECTIVE: To evaluate the associations of longitudinal trajectories of minimum JSW (mJSW) and JSW at x = 0.250 (JSW250) in the medial tibiofemoral compartment with the risk of KR among patients with symptomatic (frequent knee symptoms for at least one month in the past 12 months) and radiographic knee OA (Kellgren-Lawrence grade 2 or 3). METHODS: Using data from the Osteoarthritis Initiative (OAI) database, in which JSW was measured from baseline to the 4th visit, and again at the 6th and 8th visits, with KR status recorded over 9 visits, we applied a Bayesian joint model of longitudinal and time-to-event data to determine the association of longitudinal mJSW and JSW250 with KR risk. JSW measures were standardized to obtain hazard ratios (HRs) per 1‑SD increase. Joint models are preferred for simultaneous analysis of repeated measurements and survival data, providing less biased estimates. RESULTS: A total of 729 participants with baseline and at least one follow‑up measurement for both JSW metrics were included. After a median follow‑up of 8.84 years, 118 participants (15.97%) underwent KR. The Bayesian joint model showed that, at any time point, higher values of both measures were associated with a reduced risk of KR. Specifically, the HR per 1‑SD increase was 0.70 (95% credible interval [CrI]: 0.56-0.86) for mJSW and 0.60 (95% CrI: 0.49-0.75) for JSW250, indicating a stronger protective association for JSW250. CONCLUSION: Repeated measurements of mJSW and JSW250 provide strong longitudinal associations with KR risk, with JSW250 showing a more pronounced effect. These findings underscore the value of regular monitoring of JSW measures, particularly JSW250, in clinical practice to facilitate timely identification of knee OA patients at high risk for KR.