Radionuclide imaging of asymptomatic versus symptomatic total knee arthroplasties. Ninety-eight total knee prostheses were evaluated by roentgenograms and bone scans. Fifty-three were asymptomatic, and 45 were symptomatic. Thirteen prostheses required revision surgery. At a mean of 54 months, asymptomatic knee replacements generally showed only mild uptake in one or more zones. Only one knee had uptake equal to surrounding bone. However, symptomatic knee replacements showed significantly greater uptake in the patella, femur, and medial and lateral tibial plateau regions (Mann-Whitney two-sample rank test). Bone scans in the symptomatic group were obtained at a mean of 44 months. Excluding those patients who had revision surgery, the differences remained significant. Furthermore, symptomatic knee replacements with normal roentgenograms also had significantly greater uptake. Radiolucent lines were noted in 30% of asymptomatic patients, whereas 29% of symptomatic knees had radiolucencies. Radiolucencies were not generally associated with significantly greater uptake. Lateral release had no effect on the patellar score. 