It is recommended to use, when possible, an ultrasound guide to be sure to properly enter in the joint. It is also recommended to remove synovial fluid before PRP injection. The synovial fluid is not always present in the joint, as in the case of dry chronic joints. When present, the synovial fluid should be removed in a volume equal to the one of PRP injection. When possible, it is also recommended to wash the joint with physiological solution.