What should be known in order to practice safely a joint aspiration and/or infiltration is summarized in the following article. This summary includes various aspects, such as the indications and contraindications, the procedure itself, and the possible complications. The arthrocentesis of the knee is described in more details. Data in support of a specific modus operandi have been searched for in Cochrane and Pubmed (key words: arthrocentesis, joint aspiration). Only the conclusions of this research are exposed in this summary. A more comprehensive article will be published.