Louis ML, et al. - This study involved comparison of pain relief and functional capacity improvement among knee osteoarthritis patients who received either a single platelet-rich plasma (PRP) injection or hyaluronic acid (HA). Furthermore, biological characteristics of PRP that may affect their efficacy were also detected. Researchers found that as a management option for such patients, a single injection of very pure PRP afforded a significant clinical improvement equivalent to a single HA injection. Furthermore, they observed a significant correlation between the doses of transforming growth factor beta 1 (TGF-β1) and platelet-derived growth factor–AB (PDGF-AB) and the worsening of Western Ontario and McMaster Universities Arthritis Index (WOMAC) score 3 months after the procedure.