From the initial overenthusiasm for platelet-rich plasma (PRP) that considered it a panacea for all orthopaedic conditions to the other extreme that heavily criticized it as having a placebo effect, we are now entering a period in which significant evidence suggests that application of PRP provides clinical benefit for various indications. And although high-quality studies exist to show clinical improvement for cartilage pathologic conditions, there is not sufficient support from basic science research to explain PRP's mechanism of action or adequate characterization of its properties and behavior.