The existence of synovial fluid has been known since Hippocratic times. The abnormal accumulation of liquid inside the joints has been recognized as the proximal cause of rheumatic diseases since humoral theory was the dominant paradigm in Occidental medical culture. Although evacuating the excess of the abnormal humour was the target of all therapeutic measures taken during this era, no mention of arthrocentesis is found in Occidental medical texts until 1652. We present two earlier indications of arthrocentesis to treat abnormal accumulation of liquid inside the joints. One in the Codex Badianus, an Aztec manuscript written in the 16th century, and the other in the Tractado breve de medicina, published in Mexico in 1592.