A cadaver model was used to compare the sensitivity of fluoroscopically guided radiographs with that of plain radiographs in revealing lucent lines beneath the tibial component of an uncemented total knee arthroplasty and subsidence of the component. Fluoroscopically guided radiographs allowed accurate measurement of a lucent line that was one millimeter wide. Plain radiographs were inadequate for the detection and measurement of these lucent lines, leading to inaccuracy. Fluoroscopically guided radiographs also allowed measurement of the distance between the tibial component and radiopaque markers in the proximal part of the tibial metaphysis that was reproducible to within one-half millimeter. Plain radiographs did not provide a reproducible measurement of this distance. The relatively simple technique of fluoroscopically guided radiography is recommended to detect the presence and progression of radiolucent lines and the subsidence of uncemented tibial components after total knee arthroplasty.