Fig. 1
From: Management of failed UKA to TKA: conventional versus robotic-assisted conversion technique
a, b, c, and d Common modes of UKA failure. a Instability with ACL insufficiency causing anterior subluxation of the tibia. b Aseptic loosening with progressive radiolucent lines under the tibial baseplate. c Progressive degeneration with lateral compartment arthritis, valgus malalignment. d Progressive degeneration with patellofemoral compartment arthritis