Treatment of chronic knee effusions with 90yttrium-correlation of in vitro radiation and chemical effects with clinical results at three and six months.

Twenty seven knees, mainly of rheumatoid patients, received intra-articular 90Y for chronic effusions; 24% were effusion-free at 6 months. In vitro chemical, radiation (32P-induced), and combined effects of cold (non-radioactive) yttrium and 32P on synovial fluid mononuclear cells, failed to show any significant correlation with subjective and/or objective clinical effects at 3 or 6 months. If 90Y exerts its therapeutic effect via these cells, it probably does so other than by a direct effect on mononuclear cell viability.