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Am Fam Physician. 2022;106(6):720

Clinical Question

Are platelet-rich plasma injections, single or multiple, more effective than saline injections in adults with early symptomatic degenerative joint disease of the knee?

Bottom Line

The study is higher quality than others and finds leukocyte-poor, platelet-rich plasma injections, singly or serially, to be no better than saline injections in improving outcomes in adults with mild, radiographically confirmed degenerative joint disease of the knee. (Level of Evidence = 1b)


The authors point out that platelet-rich plasma injections are controversial because the studies, with largely negative results, have been at high risk of bias. However, the biases in those studies are generally in favor of platelet-rich plasma. The authors thought it was necessary to improve on the previous work. They recruited adults with at least four months of knee pain (with or without swelling) who had mild degeneration on radiography (if plain radiography found no signs of degeneration, magnetic resonance imaging was used to confirm the diagnosis). The participants were randomized to receive three weekly saline injections (n = 28), a single platelet-rich plasma injection followed by two weekly saline injections (n = 47), or three weekly platelet-rich plasma injections (n = 27). The researchers collected blood at each visit to be used as the platelet-rich plasma source or as a procedural disguise and blindfolded each patient to prevent unmasking of the intervention. The authors do not describe if the injections were guided by ultrasound or if a local anesthetic was used. The clinician performing the injections was unmasked but had no other involvement in the study procedures. The researchers evaluated the participants at six weeks, 12 weeks, six months, and 12 months after enrollment. Using intention-to-treat analysis applied to several standardized measures of pain, function, and quality of life, at no point in the study were platelet-rich plasma injections, singly or serially, superior to saline injections. Other than a higher risk of transient localized swelling in the participants who received platelet-rich plasma injections, the authors reported no differences in redness or bruising and that no participant experienced infections. The authors used leukocyte-poor platelet-rich plasma injections, but recent studies have found no meaningful differences between leukocyte-poor and leukocyte-rich injections in people with knee osteoarthritis.

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POEMs (patient-oriented evidence that matters) are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, see Copyright Wiley-Blackwell. Used with permission.

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