Background/Purpose: Osteoarthritis (OA) is a leading cause of chronic disability.  There are no approved treatments for modifying the disease course, therefore disease management consists of symptom control, with patients often eventually requiring joint replacement. The controversy surrounding use of the COX–2 inhibitor class of NSAIDs and heightened cardiovascular risk highlights the importance of finding safer treatment options to minimise adverse side effects, such as natural therapies.  Plant–derived therapies are traditionally used as medicines.  However, such therapies have not typically been studied with the same rigour as pharmaceutical agents.  This review summarises use of plant–derived products compared to placebo and active comparator for the treatment of OA pain and function.

Methods: 62 RCT’s of plant–based therapy for OA were identified from literature databases (PubMed, EMBASE), and summarized for pain (assessed using visual analog scores (VAS), numeric rating scales (NRS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) or Knee Injury and Osteoarthritis Outcome Score (KOOS) pain scales, function and safety outcomes using standardised mean differences (SMDs) and relative risks (RR), with trials grouped by class where possible.

Results:  Overall, plant–derived therapies are effective for treating pain compared to placebo, assessed using VAS and NRS scores (SMD 1.08; 95% CI 0.72 – 1.44), or WOMAC / KOOS pain scales (SMD 0.98; 95% CI 0.62 – 1.35).  Classes demonstrating overall efficacy in more than one trial for either VAS or WOMAC pain included Boswellia serrata, capsaicin, and ginger; there was single trial evidence of efficacy for another 9 agents (pine bark, willow bark, NR–INF–02, UP446, E–OA–07, passion fruit peel, phytalgic, Aquamin–F, SKI306X).  Plant–derived therapies have similar efficacy to active comparator (most commonly NSAIDs), assessed using VAS and NRS scores (SMD 0.32, p=0.08) or WOMAC / KOOS pain scales (-0.08, p=0.14).  Therapies are also effective for functional outcomes compared to placebo (SMD 0.92, p<0.001).  However, significant heterogeneity remains for all pain and function outcomes, indicating results need to be interpreted with caution.  Risk of adverse events was similar to placebo (RR 1.13, p=0.1), but reduced compared to active comparator (RR 0.75, p<0.001). 

Conclusion: Plant–derived therapies may be efficacious in treating osteoarthritic pain and functional limitation and appear safer than other active therapies.  However, quality trials and long term data are lacking, and the number of trials for each therapy is limited.  Comparison of efficacy would be assisted by trial standardisation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/plant-derived-products-are-effective-for-treatment-of-oa-pain-and-safer-than-other-active-therapies/