Platelet-rich plasma (PRP) has been used extensively in clinical practice to treat patients with symptomatic knee osteoarthritis (OA). Leukocyte-poor PRP (LP-PRP) has been clinically preferred over leukocyte-rich PRP (LR-PRP); however, it is unclear which cytokine mediators of pain and inflammation are present in LR-PRP and LP-PRP from patients with mild to moderate knee OA in order to rationalize a specific formulation.

In conclusion, although numerous studies have demonstrated the excellent safety profile of PRP in treating patients with knee OA symptoms, a specific formulation has yet to be determined. Although challenging to conduct, clinical trials are needed that incorporate a mechanistic approach in all study arms in order to assess the effect of all components in PRP formulations (growth factor profile, leukocytes, RBCs, platelet dose) that not only are responsible for improving symptoms but also could contribute to disease-modifying effects. Our results expand on the current literature and demonstrate novel findings in that LR-PRP that was neutrophil-rich was predominantly anti-inflammatory compared with LP-PRP with reduced neutrophil concentration in patients with knee OA.