PRP Injections May Be an Effective Treatment for Early Knee OA

    A recently published study compared outcomes of platelet-rich plasma injections with those of hyaluronic acid injections. Dr. Mehul Shah reviews the study’s key findings.


    Mehul R. Shah, MD


    Cole BJ, Karas V, Hussey K, Pilz K, Fortier LA. Hyaluronic acid versus platelet-rich plasma: a prospective, double-blind randomized controlled trial comparing clinical outcomes and effects on intra-articular biology for the treatment of knee osteoarthritis. Am J Sports Med. 2017 Feb;45(2):339-346. PMID: 28146403

    Article Summary

    The authors of this article compared the efficacy of leukocyte-poor platelet-rich plasma (PRP) injections with that of hyaluronic acid (HA) injections for the treatment of unilateral knee osteoarthritis (OA).

    Their double-blinded, prospective, randomized controlled trial included 111 patients, 49 randomized to receive PRP injections and 50 randomized to receive HA injections.

    Outcome measures, including WOMAC pain subscale, IKDC subjective knee evaluation, VAS score, and Lysholm scores, were collected before treatment and at 4 time points across a 1-year follow-up period. In addition, synovial fluid was collected and analyzed for biomarkers before treatment and at 12 and 24 weeks post-injection.

    For all outcome measures, improvement was seen from pre-treatment to post-treatment for up to 24 weeks. Results then declined from 24 weeks to the 52-week follow-up.

    The study failed to show a difference between PRP and HA injections in the WOMAC pain score at any timepoint. However, a clinical and statistically significant difference was seen in VAS and IKDC pain scores at 24 and 52 weeks, favoring PRP over HA.  

    In addition, patients with a lower BMI and mild OA had a statistically significant improvement in outcomes with either type of injection.

    Though not statistically significant, at the 12-week mark there was a trend in toward decreased concentrations to IL-1b and TNF-a in patients who received PRP injections . This decrease in pro-inflammatory cytokines preceded the improvement of subjective pain scores seen in the PRP group.

    Clinical Relevance

    Osteoarthritis of the knee is a highly prevalent condition, affecting millions of Americans. The pain associated with OA leads to disability and can have significant effects on quality of life. 

    Non-operative treatment of knee OA includes oral and topical anti-inflammatory medications, physical therapy, weight loss, and intra-articular injections. Repetitive corticosteroid injections can have deleterious affects on the articular cartilage and soft tissues about the knee, however, and physicians are therefore seeking alternative injections to help them non-operatively control the pain associated with OA. 

    HA and PRP injections have gained popularity in recent times, although there is no consensus on their efficacy. The American Academy of Orthopaedic Surgeons could not support their use in the current Clinical Practice Guidelines for the Treatment of Osteoarthritis of the Knee (Non-Surgical).

    This study by Cole et al showed efficacy of PRP and HA injections up to 24 weeks post-administration. Compared with patients in the HA group, patients in the PRP group had better results in VAS and IKDC pain scores at 24 and 52 weeks. However, no difference was seen between the 2 groups in Lysholm and WOMAC pain scores.

    Lysholm and WOMAC scores may not have been able to detect a difference because they focus on lower activity levels. In contrast, the IKDC score is an indicator of function in an athlete’s knee, and therefore may have been able to better discern the difference in outcomes between group.

    Also seen in this study was the increased improvement in patients with lower BMI and mild knee OA. Given the results of the study, PRP may be a better alternative to HA injections in more active, fitter patients with mild OA.

    This study is not without its limitations. There was no placebo injection group or comparison to the “standard” of corticosteroid injections. In addition, the study was underpowered to detect differences in biomarkers between the 2 groups. 

    Further studies should be planned to expand on the results of this very interesting study.

    Author Information

    Mehul R. Shah, MD, is an Assistant Professor of Orthopaedic Surgery, Division of Sports Medicine, at NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York.