MARCH 3, 2017
For people who have osteoarthritis (OA), knee pain severity may be a far more important predictor of long-term incident widespread pain than structural damage, according to results from Canada’s Multicenter Osteoarthritis Study (MOST). Indeed, researchers at the Université de Montréal concluded that consistent frequent knee pain, symptomatic knee OA and knee pain severity all increased the risk for developing incident widespread pain, independent of structural pathology.
“We know from previous studies that widespread pain has a significant impact on patients’ mental and physical functioning, as well as overall health,” said principal investigator Lisa Carlesso, PhD, assistant professor of rehabilitation science at the Montreal institution. “We also knew from previous studies—specifically in people with knee osteoarthritis—that there is a relationship with the presence of widespread pain, but those studies were cross-sectional and therefore weren’t able to confirm the nature of the relationship. Due to the health implications of widespread pain, we were interested in performing a longitudinal study to see whether people with knee osteoarthritis were at increased risk for developing widespread pain.”
Dr. Carlesso and her colleagues analyzed data from the MOST study, a longitudinal cohort of 3,026 patients either suffering from, or at risk for developing, knee OA. Using their 60-month visit as a baseline, 1,129 participants (52% women; mean age, 66.7±7.8 years; body mass index, 30.1±5.8 kg/m2) were characterized on several clinical factors, including consistent frequent knee pain, radiographic OA (Kellgren–Lawrence grade ≥2), symptomatic knee OA and knee pain severity.
Widespread pain—which excluded knee pain—was defined as pain above and below the waist, on both sides of the body and axially. Incident widespread pain was defined as presence of widespread pain at 84 months among participants who did not have widespread pain at baseline. Logistic regression was used to analyze the relationship of baseline radiographic OA, symptomatic knee OA, consistent frequent knee pain and knee pain severity to incident widespread pain, adjusting for potential confounders including models with and without pain severity.
The investigators found that radiographic OA in either knee was not associated with incident widespread pain (adjusted odds ratio [aOR], 0.90; P=0.587). Conversely, baseline bilateral consistent frequent knee pain (aOR, 2.35), bilateral symptomatic OA (aOR, 2.11) and knee pain severity in the worst knee (aOR, 1.11; P<0.001) were all significantly associated with incident widespread pain.
“It turns out that people with knee osteoarthritis do have an increased risk for developing widespread pain, though this is mainly due to the severity of the pain and not how bad the knee looks on x-ray,” Dr. Carlesso told Pain Medicine News. “Our findings confirm that having a localized condition such as knee osteoarthritis can lead to the onset of more widespread pain throughout the body.”
In view of the results, Dr. Carlesso stressed the importance of effective pain management in these people. “Clinicians should be aware that patients who report more severe pain related to their knee osteoarthritis are at risk for having that pain spread more widely to other parts, and it is therefore very important to manage the pain effectively to help minimize that risk.”
She suggested that pain sensitization likely plays a role in the development of incident widespread pain. “We need greater exploration of mechanism-based pain management strategies to improve overall pain management for people with knee osteoarthritis,” Dr. Carlesso said.
Roland Staud, MD, told Pain Medicine News that while the results of the study did not come as a particular surprise, they help illustrate the importance of early intervention. “It is now clear from the literature that widespread pain generally begins as localized acute pain,” said Dr. Staud, professor of medicine at the University of Florida in Gainesville, and a Pain Medicine News editorial advisory board member.
“For example, one factor that’s very important for worsening of chronic pain is that significant pain events like surgery need to be much more effectively treated, particularly postoperative pain, which is not always perfect,” Dr. Staud said. “So these are some of the preventable pain episodes that likely contribute to worsen the chronic pain state over time.”
—Michael Vlessides