Primer: pitfalls of aspiration and injection.

This review on joint aspiration and injection focuses on three common clinical problems: how to deal with 'dry taps', especially when a septic joint is suspected in the differential diagnosis; how to avoid rare complications associated with these techniques; and how to reduce pain in patients who are particularly sensitive. Solutions to these problems are proposed, and although no new data or insights are provided, this article could be used as a noncomprehensive check list for trainee rheumatologists. This review focuses on the knee, because of the common appearance of septic joints in the differential diagnosis of inflammatory knee effusion, and the paramount importance of septic joints in this setting. The five reasons for failing to aspirate fluid from a difficult knee joint that are discussed here could be applied to other more problematic joints, such as the elbow or ankle. Some additional time-consuming techniques involving more than one syringe and two operators might not be cost effective in many situations, but these should be taught for use in selected cases in which pain hinders aspiration. Training should also be provided to ensure that rheumatologists never inject against pressure, and that they switch to the lateral approach when aspirating the knee if their first attempt fails, especially if a septic joint is suspected and fluid must be obtained for diagnosis.