X-rays of the knee joint of a 59 year old male patient undergoing treatment for chondrocalcinosis, or pseudogout. A contrast medium (white) and anti-inflammatory drug are being injected into the joint. The contrast medium helps to guide the needle to the correct location. In chondrocalcinosis, crystals of calcium pyrophosphate are deposited in soft tissues such as cartilage, the connective tissue found in joints. Affected joints are red, swollen and extremely tender.