Loosening of the prosthesis and infection are the most common late complications of the Charnley low friction arthroplasty. A noninvasive diagnostic approach to the symptomatic patient, using plain radiographs and nuclear imaging with a bone imaging agent, is presented. Nuclear imaging is a more sensitive indicator than plain radiography, but the 2 studies supplement each other. The nuclear study may be positive when radiographs are normal and in no patient with loosening was the nuclear image normal. In the presence of a normal nuclear image and a normal radiograph there is an extremely small probability that either complication is present.