medwireNews: Advanced knee pain patterns involving constant plus intermittent pain are associated with increased severity of pain and radiographic knee osteoarthritis (OA) duration and severity, suggest longitudinal study data.
This compares with other patterns, such as no pain, intermittent pain only, and constant pain only, notes the team in Arthritis Care & Research.
“These results point to the likelihood that pain severity itself is not an adequate metric to understand the stage of symptomatic OA disease,” say the researchers, who emphasize: “This speaks more broadly to the need to understand other pain dimensions, such as these pain patterns.”
Lisa Carlesso (McMaster University, Hamilton, Ontario, Canada) and colleagues analyzed data pertaining to 2322 individuals (4632 knees), aged an average of 68.8 years, who had OA of the knee or were at risk for the condition and had reported knee pain in the 30 days prior to their 60-month check-up.
For most knees, at 62%, the pain in the 7 days prior to the 60-month check-up did not meet the criteria for a constant or intermittent pattern, based on patient-reported scores on the 11-item Intermittent and Constant OA Pain (ICOAP) measure. However, intermittent pain of at least mild severity and a frequency of at least sometimes was reported for 30% of knees, while constant pain of at least mild severity was reported for 4% of knees, and both constant and intermittent pain for a further 4%.
Patients with both constant and intermittent pain were 43 times more likely to have greater severity of pain than those with neither pain pattern according to the WOMAC pain subscale and 71 times more likely according to the VAS pain subscale, the researchers report.
Similarly, patients with constant pain were 3.8 and 4.7 times more likely to report both severe and mild-to-moderate pain according to the WOMAC and VAS pain subscales, respectively, than those with only intermittent pain.
Worsening pain patterns were also associated with increasing severity and duration of radiographic OA, with the likelihood of combined constant and intermittent pain rising in line with higher Kellgren–Lawrence grades.
A finding that Carlesso and team say “supports a relationship between the pain experience and its association with [radiographic OA] severity and duration, which have had conflicting correlations with pain severity.”
Indeed, patients with severe radiographic OA – Kellgren–Lawrence grades of 3 to 4 – were a significant 3.7 times more likely to have combined constant and intermittent pain than those with grade 0, while the likelihood was increased by a significant 1.3 and 2.0 times for those with grades 1 and 2, respectively.
In the case of OA duration, patients who had had the condition for more than 60 months were 1.4 times more likely to have constant than intermittent pain, compared with individuals without OA.
“This provides, for the first time, proof-of-concept evidence that these pain patterns do indeed track with OA structural disease,” say the researchers.
“Our data suggest that clinicians may be able to use the ICOAP as a tool to effectively track knee OA progression, and this approach may potentially help mitigate the so-called ‘structure-symptom’ discordance.”
They conclude that “[s]tudies are needed to understand what may trigger the transition to more advanced pain patterns.”
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