Opioid users with osteoarthritis of the knee (KOA) had poorer baseline knee structural degeneration and faster progression, according to a study. The results were published in Arthritis Research & Therapy.
Participants were identified from the Osteoarthritis Initiative cohort. They had baseline opioid use (n=181) and continued use for at least one year between baseline and four-year follow-up (n=79). Researchers collected Whole-Organ Magnetic Resonance Imaging Scores (WORMS), including a total summation score (WORMS total, range 0–96) and subscores for cartilage (0–36), menisci (0–24), and bone marrow abnormalities and subchondral cyst-like lesions (0–18, respectively); Knee Injury Osteoarthritis Outcomes score (KOOS) symptoms; quality of life (QOL); and pain, at baseline and follow-up (range 0–100; lower scores indicate worse outcomes). Analyses were performed adjusting for sex, BMI, age, race, and Kellgren-Lawrence grade.
Opioid Use Tied to Poorer Outcomes Across the Board
Opioid users, compared to controls, had significantly worse structural degeneration at baseline, with a WORMS total of 7.1, as well as greater increase over follow-up (4.7). Users also had greater increases in cartilage and meniscus scores, regardless of baseline pain. They further had lower KOOS scores, and greater QOL loss when adjusting for baseline KOOS pain.
Discussion, Study Limitations
Opioid use is “controversial,” the researchers acknowledged. Generally, opioids are not recommended for pain control in osteoarthritis. Still, prescription rates in the United States are estimated at around 16%.
“Particularly with regard to the known adverse effects and risk of addiction, opioid use for long-term pain management in KOA should be critically questioned,” the study authors acknowledged.
The study had several limitations, mainly that patients with worse KOA and worse symptoms are more likely than those with less severe disease to use opioids. The researchers also acknowledged that the use of WORMS scores as outcomes was a limitation, one that could be addressed using “continuous, truly quantitative data, such as cartilage thickness measurements.” There was also a small number of eligible opioid users for the study. Finally, the researchers used KOOS scores, rather than a different QOL assessment. This decision was made, however, because “the KOOS was designed to specifically address knee-related QOL.”
The researchers wrote in their conclusion, “Opioid medication in KOA is associated with worse baseline structural degenerative disease and also with faster progression of degenerative changes. Despite the use of opioids, baseline symptom and pain control were worse in opioid users compared to controls. Loss of QOL was more rapid in opioid users, when adjusted for baseline pain scores, further questioning long-term opioid use, particularly in view of major adverse effects associated with this medication.”