Sit RWS, Wu RWK, Law SW, et al. - Through a prospective 26-week single-arm uncontrolled feasibility pilot study of patients (n = 12) with primary knee osteoarthritis (KOA) as defined by the American Rheumatology Association, with moderate to severe medial knee pain which failed conservative management, the researchers intended to pilot test a leukocyte-rich (mononuclear cells) Platelet Rich Plasma (PRP) injection protocol for primary KOA, which consisted of single intra-articular injection and extra-articular injections on the medial coronary and medial collateral ligaments. In 3 months term, 12 of 40 potential patients were involved. Each individual stuck to the protocol and completed the follow-up evaluation with no dropouts. Satisfaction was huge and no related adverse events were reported. Most secondary outcomes exhibited statistically important progress. Therefore, concomitant intra-articular and extra-articular PRP injections were concluded to be worthwhile and gave preliminary favorable outcomes.