As RSO is a second- or even third-line treatment. All patients need undergo extensive diagnostic workup before RSO to exclude other causes such as mechanical loosening, instability, TKR malposition or infection.

Based on its physiochemical properties, 90-yttrium (Y-90) is the radionuclide of choice for RSO of the knee joint (Fig. 38.1). Y-90 is available as Y-90 citrate and Y-90 silicate. Both radiopharmaceuticals show different stability and drainage from the joint. Due to longer deposition in the knee, some authors like Gumpel et al. recommended Y-90 silicate [6]. Y-90 is a pure ß-emitter. The therapeutic ß-radiation penetrates the synovial membrane by 3.6 mm in the mean and by 11 mm in the maximum. The half time is 64 h, and the maximum energy emitted is 2.27 MeV [20].

The tracer is injected intra-articularly under aseptic conditions. Fluoroscopy is used to facilitate the correct needle position (Figs. 38.2, 38.3 and 38.4). In addition to the tracer, 10–20 mg of a glucocorticoid suspension like triamcinolone acetate is injected (Figs. 38.4 and 38.5). This glucocorticoid aims to reduce the radiation-induced synovitis and the risk of leakage by reduction of hyperperfusion and vascular permeability [10]. It also avoids tracer backflow into the needle. If there are any reasons not to apply steroids, it is necessary to flush the needle with saline solution to prevent backflow and to minimize the risk of radionecrosis.