A meta-study that included 137 studies comparing the effectiveness of treatments for osteoarthritis (OA) of the knee showed that acetaminophen, the most widely used over-the-counter medication, did not provide significant pain relief. “With the exception of celecoxib, all active interventions were significantly superior to acetaminophen. Intra-articular placebo was significantly better than oral placebo, and effective intra-articular treatments were more effective than aggressive oral medications,” said Dr. Raveendhara R. Bannuru of Tufts Medical Center in Boston, Mass. “Most treatments did not differ significantly in improving function and stiffness, in part because of the limited number of studies comparing many interventions.” Study results January 6 published in the Annals of Internal Medicine. The efficacy of various therapies was compared in the study, with oral medications including acetaminophen, celecoxib, diclofenac, ibuprofen and naproxen; and intra-articular injections of corticosteroids or hyaluronic acid, and oral and injectable placebos. Studies were included in the relevant literature published between 1980-2014, including 33,243 patients. of 137 studies, 129 studies (32,129 participants) evaluated pain, 76 studies (24,059 participants) analyzed function, and 55 studies (18,267 participants) evaluated stiffness. All treatments provided some relief of knee OA pain at 3 months compared with oral placebo. Hyaluronic acid was the most effective, with an effect size of 0.63. Acetaminophen was the least effective, with an effect size of 0.18, and did not meet the predetermined threshold for clinical significance. In terms of pain reduction, injections were more effective than oral therapies, and placebo injections were more effective than oral non-steroidal anti-inflammatory drugs. In terms of improving stiffness, naproxen, ibuprofen, diclofenac, and celecoxib were more effective than oral placebo and acetaminophen, and hyaluronic acid injections were more effective than placebo injections. However, injectable placebo was not significantly better than oral placebo. For improving function, all interventions except injectable corticosteroids were better than oral placebo.