Six ACE Reports (5 randomized controlled trials and 1 systematic review/meta-analysis) were identified from the OrthoEvidence database which evaluated the efficacy of platelet-rich plasma in the treatment of knee osteoarthritis. All included studies were randomized controlled trials, and reported clinical and functional assessment at various time points between 1 and 6 months following treatment. Pooled analysis of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Total scores suggested a possible beneficial effect with PRP injection in comparison to saline and a lower effect versus hyaluronic acid. Beneficial effects were also noted for individual subscales of the WOMAC assessment (pain, stiffness, and physical function). However, pooling of OMERACT-OARSI responders and a review of the literature indicated that there was no significant difference between PRP and comparison groups in other functional outcome measures, such as the International Knee Documentation Committee (IKDC) assessment and Knee Injury and Osteoarthritis Outcome Score (KOOS). Furthermore, contrasting results were obtained between two studies reporting function on the Lequesne Index. The discrepancy in the efficacy of PRP in treatment for osteoarthritis of the knee indicates the need for future high-quality randomized trials, with uniform reporting, in order to provide further evidence in this emerging treatment method.