If osteoarthritic degeneration is limited to solely the medial aspect of the knee, UKR can be a fantastic way to return patients back to their normal way of life with less trauma than a total knee replacement. UKR's have a fixed or a gliding mobile bearing an example of which can be seen highlighted in the images above. The top 2 images show the bearing nicely situated 2 days after surgery. The vast majority of these UKR's give great outcomes without major complications but unfortunately that isn't the case here. 5 weeks post op our patient slipped and forced her knee into full flexion causing a sharp pain and inability to weight bear. The bottom two images show that the mobile bearing has been displaced posteriorly causing a lack of congruency to the prosthesis resulting in pain and reduced weight bearing tolerance. The patient was readmitted for a minor procedure to revise the bearing and made a good recovery, returning to full ADLs 3 weeks after.