6 randomized controlled trials (RCTs) and 4 non-randomized clinical trials with a total of 1110 patients were included in this systematic review and meta-analysis to determine the effectiveness of platelet-rich plasma (PRP) injections in patients with osteoarthritis (OA) of the knee. Results demonstrated a significant reduction in pain in patients treated with PRP compared to patients treated with placebo or hyaluronic acid injections. Additionally, WOMAC physical function was also seen to significantly favor PRP treatment in comparison to the placebo and hyaluronic acid injection groups. Results from the systematic review and meta-analysis should be interpreted with caution as the majority of the trials included were associated with a high risk of bias and there was significant heterogeneity in the outcomes assessed.