Bacterial biofilm infections of artificial knees are treated by mixing antibiotics into bone cement and calcium sulfate beads. We designed a knee size model to show that cement alone killed biofilms on orthopedic materials and prevented their spread close to the cement, but adding beads significantly killed biofilms further away. The model is useful in helping show how both the spread and the amount of antibiotic carrier can kill biofilms that might be in different places in the joint.