August 15, 2022
2 min read
The authors report grant support from the National Institute of Health, the Pfizer Global Award for Advancing Chronic Pain Research and the Rheumatology Research Foundation.
Even modest osteoarthritis pain reductions through intervention would substantially reduce the number of knee replacements, according to data published in Arthritis & Rheumatology.
“The Global Burden of Disease (GBD) reports OA as a leading cause of disability and the most common form of arthritis that affects roughly 91.2 million adults in the United States,” S. Reza Jafarzadeh, DVM, MPCM, PhD, of the Boston University School of Medicine, and colleagues wrote. “The rising rates of obesity and aging of the population will only exacerbate the need for a [knee replacement (KR)] that is expected to overwhelm the U.S. health care system in coming decades. Painful knee OA affects about 4.9% of the United States population age 26 and over, and 16.7% of those age 45 and above.
“Randomized trials testing efficacy of OA treatments often consider pain improvement as the primary efficacy target,” they added. “It is uncertain however, what amount of pain improvement would be needed to ultimately reduce the risk of a KR.”
To investigate whether knee pain interventions might have any impact on the number of knee replacements performed, Jafarzadeh and colleagues analyzed data from the Osteoarthritis Initiative, a longitudinal, multicenter cohort of patients with or, at risk for, OA. The cohort included data from baseline and 12, 24, 36, 48, 72 and 96 months. The study outcome was the presence of total or partial incident knee replacements as recorded in the OA Initiative.
Hypothetical interventions were defined as any treatment that resulted in a reduction of pain, as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Interventions included medications, physical activity and weight loss.
The researchers modeled hypothetical reductions in the WOMAC subscale when patients reported pain levels of five — out of 20 — at any visit to the clinic. The authors estimated the risk for a knee replacement based on pain scale observations, as well as the potential change in risk if various interventions would be employed. Patients’ real-world knee replacement outcome was compared with a predicted outcome if interventions were employed at any timepoint when patients reported a pain level of five or greater.
The researchers examined data on 9,592 knees from 4,796 participants. Of those, 40.7% reported WOMAC pain of five or greater. The authors estimated an adjusted reference risk for knee replacement as 6.3% (95% CI, 5% to 7.7%).
According to the researchers, a one-point pain reduction lowered the risk for knee replacement from 6.3% to 5.8%. Meanwhile, a reduction of two points lowered the risk down to 5.3%, while a three-point reduction brought it to 4.9%. Additionally, the researchers noted larger reductions in knee replacement risk when interventions were applied for patients reporting a pain score of four or greater.
“KR rates are increasing, straining the capacity of the health care system and also health care budgets,” Jafarzadeh and colleagues wrote. “While trials of potential treatments for OA do not generally have long enough follow-up or sufficient size to evaluate the effect of pain reduction on KRs, our findings suggest that treatments with even modest reductions in pain commensurate with current treatments would substantially decrease KR rates. These data provide additional strong evidence that effective treatments for OA are critically needed.”