PSMA Uptake Due to Recent Intra-articular Injection.

We report a case involving a 66-year-old man with prostate adenocarcinoma, referred for initial staging using 99m Tc-PSMA and 99m Tc-MDP bone scan. The whole body PSMA scan revealed foci of increased tracer uptake in the right knee and the surrounding periarticular space above the knee. Subsequent 99m Tc-PSMA SPECT/CT imaging demonstrated evidence of arthritis characterized by effusion in the periarticular region, connected to the joint in the right knee. Notably, the patient had received an intra-articular corticosteroid injection just 2 days before the scan. This case highlights the necessity of recognizing atypical 99m Tc-PSMA uptake patterns to differentiate from metastasis, thereby enhancing diagnostic accuracy.