Kinsey TL, et al. - Experts compared the progression of radiographically evident osteoarthritis in unoperated compartments during 5 years after lateral and medial unicompartmental knee arthroplasty (UKA). In evaluating patients with isolated lateral compartment disease, the propensity for faster disease progression after UKA should be considered. Over time, an increase in all mean disease grades for the tibiofemoral (TF) and patellofemoral (PF) compartments was seen. For lateral UKA in the TF and PF compartments, the adjusted rate of Kellgren grade change was statistically faster, as was Ahlbäck change in the TF compartment.