Lange JK, et al. - This study investigated Short Form 36 Physical Component Score (PCS) trajectories of 656 individuals composed of 3-time points over a 1-year period. Two different clusters of outcome trajectories were recognized. Cluster 1 comprised 550 patients who exhibited persistent PCS betterment at 6 and 12 months. Cluster 2 comprised 106 patients who exhibited a drop in PCS at 6 months succeeded by betterment at 12 months. Cluster 1 succeeded early, had greater absolute mental and physical health scores in comparison with Cluster 2, and exhibited higher baseline mental health scores, lower baseline PCS, and a significantly greater proportion of non-Hispanic Whites. Therefore, Cluster analysis determined different functional outcome trajectories after TKA. Moreover, specific distinguishing patient factors were correlated with varying trajectories.