Dislocation of the polyethylene component in knee arthroplasty is a rare complication. The main triggering factor is failure of the locking mechanism, which may result from technical errors of insertion, trauma or even implant failure. Here, a case of dislocation of the polyethylene component from the tibial base, nine years after revision arthroplasty, is reported. It is believed that this is the first such case reported in the Brazilian literature.