Platelet-rich plasma injections for knee osteoarthritis: Systematic review of duration of clinical benefit

Both researchers and clinicians have exhibited growing interest in the use of platelet-rich plasma (PRP) and other autologous products for a variety of clinical conditions. Newly published data suggest that PRP injections can be an effective complement to conventional management strategies for knee osteoarthritis (OA) and chondropathy. Using a systematic review approach, we sought to synthesize the published data on the duration of clinical effect of PRP on knee OA and chondropathy. We systematically searched PubMed for all reports published in any language between the earliest available date and July (fourth week) of 2015 using the following key words: platelet, rich, plasma, knee, and osteoarthritis. If double-blind randomized, controlled trials were not available, we included other clinical trials and observational studies. We further searched for the association of the same keywords (platelet, rich, plasma, knee) and chondropathy. After reviewing abstracts, we acquired full-text papers where appropriate. We categorized the level of evidence for the duration of treatment efficacy according to Guyatt and coauthors. Twenty-four relevant studies encompassing 2,385 patients were included in the review. Studies reported clinical outcomes from intra-articular injection of PRP or recounted autologous products. The results showed a consistent improvement in patient pain scores and functional indexes for 6 months after initiation of injections. The residual clinical effect was typically observed beyond 6 months of follow-up in most of the studies. Pain and functional scores decreased after 12 months of follow-up but remained higher than the base scores in the majority of studies. Some suggested that annual injections improved treatment outcomes after 18 months of follow-up. Data from available clinical reports suggest that the PRP administration results in decreased pain and enhanced functional status. The duration of beneficial clinical effects after administration of PRP or recounted autologous products for patients with knee OA and chondropathy was stable up to 6 months following completion of regenerative therapy. The pain and functional scores worsened after 12 months of follow-up but were still better than pre-injection scores according to the majority of publications. The analysis is limited by the wide variability of available studies.