By Pat Anson, PNN Editor

Cannabidiol (CBD) is often touted as an effective pain reliever for arthritis. Studies on animals and anecdotal reports from humans suggest that CBD – the non-psychoactive compound in cannabis -- has anti-inflammatory and pain-relieving effects on joint pain.

But in one of the first randomized, placebo-controlled clinical trials of CBD, researchers at Medical University of Vienna found that CBD is not an effective pain medication for knee osteoarthritis, even at high doses.

The study included 86 men and women who suffered from severe pain due to knee osteoarthritis,  a progressive condition caused by the breakdown of joint cartilage.in the knee. About 10 percent of people over age 60 have knee osteoarthritis (OA).

Half the participants received daily doses of CBD in capsules for eight weeks, titrating up to 600mg per day, which is considered a high dose. The other participants were given placebo capsules with no active ingredient. Neither group knew what they were taking.

The study findings, published in The Lancet Regional Health -- Europe, show that CBD did not have a stronger analgesic effect than the placebo. Adverse events were more common in the CBD group, with over half the participants (56%) reporting diarrhea, abdominal pain, fatigue and other mild side effects.

“Our results do not support the yet clinically unproven hopes for CBD as potential supplement or even replacement of potent analgesics, including opioids,” wrote lead author Sibylle Pramhas, MD, Department of Special Anesthesia and Pain Medicine at MedUni Vienna.

"Our study is the first to provide solid information on the lack of analgesic potential of CBD in a common chronic pain condition, due to the comparatively high oral dosage and the long observation period.”

This isn’t the first time CBD came up short in a clinical study. In 2017, Zynebra Pharmaceuticals tested a CBD gel for knee OA with mixed results. The Phase 2 study did not meet its primary goal of reducing the average pain score, although there were some indications the gel improved function and reduced pain severity. The company has since abandoned plans to use the gel for arthritis pain.

A more recent study of a CBD patch for knee osteoarthritis was withdrawn due to “inadequate funding.” Several other clinical studies of CBD for OA pain are underway or recruiting participants, but no results have been posted.

Currently, osteoarthritis knee pain is treated with analgesics such as acetaminophen (paracetamol), diclofenac, ibuprofen or tramadol. For the time being, they may be the best alternatives for pain relief.   

"CBD is not an alternative for pain therapy for osteoarthritis of the knee, so the search for more effective options must continue," says Pramhas.