About one in seven people will eventually develop osteoarthritis of the knee, and the proportion is likely to rise as the population gets older and the obesity epidemic takes its toll on our aging knees. Unfortunately, there is no cure and no clear winner among the many drugs used to treat the condition. Part of the problem is that there have been few studies comparing treatments.
Researchers from Tufts and Brown universities attempted to fill in some of the blanks by doing a special analysis of 137 placebo-controlled studies on knee arthritis in order to evaluate the relative efficacy of four leading drugs and two common types of injections. The results, published in January 2015 in the Annals of Internal Medicine, contained some surprises:
- Acetaminophen, the most commonly recommended and used drug for arthritis (Tylenol is one brand), was least effective in relieving knee pain after three months—only minimally better than a placebo.
- Best of the oral drugs for pain relief was diclofenac (prescription only), followed by ibuprofen and then naproxen. Celecoxib (Celebrex, prescription only) was just slightly more effective than acetaminophen. There was little or no difference in the effect of the drugs on stiffness and function, largely because of limited data.
- Most effective for pain were injections of either corticosteroids or hyaluronic acid into the joint, compared to an injected placebo—and even more effective when compared to an oral placebo.
- Interestingly, injected placebos provided much more pain relief than oral placebos and were at least as beneficial as the oral drugs. It's well known that the placebo effect plays a large role in treatments for arthritis and other kinds of pain. That is, positive expectations about a treatment—even if it actually is just a sugar pill or saline injection—can trigger an improvement in symptoms. Injected placebos may be more effective because patients expect more from them, or it may be that injecting any fluid into the joint provides some relief.
Bottom line: If you have knee arthritis, discuss your treatment options with your health care provider. People respond differently to treatments partly because arthritis pain can have different causes. Many providers still advise patients to start with acetaminophen, since it will help some of them and is least risky when taken as directed. However, acetaminophen overdosing (more than 4,000 milligrams a day) can cause severe liver damage, as can lower doses when combined with alcohol. If oral drugs don’t help enough, ask about knee injections.