Adding a synthetic weed-derived drug to opioid painkillers brings no relief to people with excruciating knee pain, a new study says.
Neither the cannabis drug dronabinol nor the opioid hydromorphone alone provided significant pain relief for people with knee arthritis, and combining them did not improve results, researchers reported recently in the journal Anesthesiology.
“Some patients believe combining cannabis with opioids can help with pain, and clinicians may recommend or prescribe it in states where cannabis is legal,” said lead researcher Katrina Hamilton, an experimental psychologist at Ohio University in Athens.
“Our study suggests that isn’t the case and patients may experience more side effects when the drugs are combined,” Hamilton said in a news release.
Dronabinol is a man-made form of tetrahydrocannabinol (THC), the chemical compound in weed that produces intoxication, according to Drugs.com.
For the new study, researchers recruited 21 patients with knee arthritis. Each person took part in four sessions in which they were given different combinations of pills:
After taking the pills, the patients underwent tests to see how the drugs affected pain.
Results showed that opioids and cannabis, either alone or together, did not provide robust relief for knee pain. Further, opioids reduced pain sensitivity but did not meaningfully reduce participants’ self-reported pain. Cannabis didn’t appear to help at all.
There was no added pain relief when the two drugs were combined, but there were stronger and more noticeable side effects like drowsiness, dizziness, and impaired thinking, researchers said.
However, researchers noted that these results might not fully represent how people use weed in real-world situations.
“In the real world, people often use cannabis differently, including lower starting doses, using gradually stronger doses, which may affect both benefits and side effects,” Hamilton said. “More research is needed to better understand how cannabis affects pain when used in real-world settings.”
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Research shows that Black adults are more likely to experience severe osteoarthritis pain and physical limitations from arthritis than many other groups. At the same time, Black patients have historically faced barriers to adequate pain treatment, leading many to explore alternative options, including weed.
As more states legalize medical marijuana, some people living with chronic knee pain may wonder whether combining cannabis with prescription pain medications could provide better relief. These latest findings suggest that this approach may not offer the most benefits, and might even increase unwanted side effects.
There isn’t a one-size-fits-all approach to relieve knee arthritis pain. Depending on your symptoms, options may include:
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Many people managing chronic knee arthritis are searching for alternatives to opioids, and cannabis has gained attention as a possible solution. However, the latest research suggests that combining the two may not provide additional pain relief and could increase side effects such as dizziness, drowsiness, and impaired thinking. For Black Americans who are disproportionately affected by arthritis-related disability, evidence-based pain management remains the safest path forward.
More information
Harvard Medical School has more on controlling knee pain.
SOURCE: American Society of Anesthesiologists, news release, April 20, 2026
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