BACKGROUND: Evaluate functional and participation predictors of outcome following knee arthroplasty (KA) focusing on theInternational Classification of Functioning, Disability, and Health framework. METHODS: Secondary analysis of the CORKA randomised controlled trial, which included patients undergoing KA. The primary outcome was the Late-Life Function and Disability Instrument (LLFDI) was assessed using a linear mixed-effects model. Secondary outcomes with baseline assessments of the Physical Activity Scale for the Elderly (PASE), Figure of 8 Walk Test (F8WT), 30-Second Chair Stand Test (30CST), and single-leg stance on the operated leg (SLS) were used to predict functional and participation outcomes at 6, 12, and 24-months using multiple linear regression models. RESULTS: 621 participants were recruited (males 250, females 371), with a mean age of 70 ± 8 years. SLS significantly predicted LLFDI function across all time points (6-months 0.14, 0.06-0.22, p = 0.001, 12-months 0.18, 0.09-0.27, p < 0.001, 24-months 0.21, 0.11-0.31, p < 0.001), while PASE predicted it at 6-months 0.02, 0.01-0.03, p = 0.006 and 24-months 0.02, 0.004-0.04, p = 0.012. PASE also predicted disability frequency at all intervals(6-months 0.03, 0.02-0.05, p < 0.001, 12-months 0.04, 0.02-0.05, p < 0.001, 24-months 0.03, 0.01-0.05, p = 0.001), with SLS and F8WT as significant predictors at 12 and 24-months, respectively (SLS 12-months 0.13, 0.04-0.21, p = 0.005, F8WT 24-months -0.37, -0.73 to -0.01, p = 0.044). Only PASE (12-months 0.04, 0.01-0.07, p = 0.003, 24-months 0.04, 0.01-0.07, p = 0.003) and SLS (12-months 0.26, 0.10-0.42, p = 0.002, 24-months 0.28, 0.12-0.44, p = 0.001) predicted disability limitation at 12 and 24-months. CONCLUSIONS: Findings suggest functional measures may be used to predict short-term outcomes, while participation measures better suit long-term outcomes after KA.