Significance of a "hot patella" in total knee replacement without primary patellar resurfacing

A "hot patella" is a bone scan finding of increased tracer uptake in the patella, greater than the ipsilateral distal femur or the proximal tibia. Increased patellar uptake on the bone scans is a relatively frequent finding; this is often not commented upon. The aim of our study was to define the incidence of a "hot patella" on bone scans following total knee replacements with ongoing symptoms unrelated to sepsis. We wanted to investigate the correlation between the adverse retropatellar symptomatology following total knee replacement with bone scan findings. We undertook a retrospective study of 55 symptomatic total knee replacement patients, who had bone scans. The incidence of a "hot patella" in patients without primary patellar resurfacing was 51% (28/55). Ninety-five percent patients with anterior knee pain and 21% patients with diffuse knee pain had a "hot patella". Statistical analysis showed a positive association between "hot patella" and anterior knee pain (p value of <0.001). The patients with "hot patella" who underwent secondary patellar resurfacing had symptomatic relief of symptoms. Our study has shown that the finding of a "hot patella" on a bone scan in patients with anterior knee pain following total knee replacement suggests a problem related to the patellofemoral joint. This study would appear to indicate that a "hot patella" in a patient with clinically defined anterior knee pain is likely to benefit from secondary patellar resurfacing.