Management of knee osteoarthritis: an evidence-based review of treatment options

Osteoarthritis is the most common form of arthritis, and its incidence increases rapidly with age. Osteoarthritis is a progressive degenerative disease, and treatment must evolve with disease progression. Several classes of medications and treatment modalities have been used to relieve pain and preserve function. Most have been studied extensively but results of even well-designed trials can diverge. Furthermore, effect of a drug (beneficial or adverse) in an individual patient is not always predictable and may differ from the class effect. A short treatment trial may be necessary to determine efficacy. This potential discrepancy between statistical outcome and individual result is captured in the guidelines, to whatever extent possible. A summary of recommendations for select interventions compiled from multiple guidelines is presented in table II. In closing, interpretation of guideline recommendations, and how they were derived, must be clarified, since they have been a source of confusion and misinterpretation. Level of evidence (LoE) refers to the source from which the evidence was derived. It describes the quality of evidence and academic vigor, with meta-analysis of RCT being of strongest quality and expert opinion the lowest. The strength of effect describes how much of a clinical effect (usually benefit) is expected from the intervention. The strength of recommendation incorporates LoE and strength of effect, as well as cost, safety, and feasibility. An intervention with a high LoE does not necessarily trigger a strong recommendation. For example, NSAIDs have a greater effect on pain reduction than acetaminophen in most studies, but carries a lower recommendation due to concerns with long-term safety. Total knee arthroplasty has a LoE of III since no blinded RCT have studied the procedure, yet it carries a strong recommendation in advanced OA. In the five years between the publication of the EULAR and the OARIS guidelines (2003-2008), new studies were published explaining, in part, the difference in recommendations among the agencies. Future guidelines will undoubtedly evolve further.