From Medscape Education Clinical Briefs
News Author: Norra MacReady
CME Author: Désirée Lie, MD, MSEd
March 25, 2011 — Coexisting depression is an independent predictor of pain among people with radiographic evidence of mild to moderate osteoarthritis of the knee, researchers in South Korea have found.
"The contribution of comorbid depression to knee osteoarthritis symptoms [KOAS] is almost equal to that of radiographic severity," senior author Tae Kyun Kim, MD, told Medscape Medical News.
"As this finding is particularly important for mild to moderate knee osteoarthritis, due consideration for the presence of depression should be given to patients who suffer irrationally severe or persistent symptoms from mild to moderate knee osteoarthritis."
Dr. Kim and his colleagues at Seoul National University Bundang Hospital in Seongnam, South Korea, decided to conduct their study after observing that elderly people with knee arthritis show a substantial disparity between radiographic findings and reported pain levels.
This suggests that "the perception of pain in arthritis is influenced by factors other than the degree of osteoarthritic joint damage," they explain in an article published online March 16 and in the March issue of the Journal of Bone and Joint Surgery. Because depression is common in elderly people, the researchers suspected it might account for some of that discordance.
The patients were participants in the Korean Longitudinal Study on Health and Aging, a population-based, prospective cohort study on health, aging, and common geriatric illnesses seen in elderly Koreans.
Of the 1000 study volunteers, 660 (368 women and 292 men) had completed a radiographic examination of the knee, symptom evaluation using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and diagnostic interviews for depression. The patients all were aged 65 years or older, with a mean age of 71.5 years and a mean body mass index of 24.3 kg/m2.
The WOMAC system consists of a 24-item questionnaire that evaluates pain, stiffness, and function. The highest possible score is 96; symptomatic knee osteoarthritis is defined as a score of at least 39. Patients also completed a short-form 36 scale that assessed health-related quality of life.
Of the 660 patients, 556 were KOAS-positive, and 104 were KOAS-negative. KOAS-positive patients were older (P < .001), more likely to be female (P < .001), and had a higher body mass index (P < .05) than their KOAS-negative counterparts. Their prevalence of depressive disorders was 26.9% compared with 5.8% in the KOAS-negative patients (P < .001). KOAS-positive patients also had a poorer health-related quality of life on the short-form 36, and more depressive symptoms (P < .001 for both).
On logistic regression analysis, the presence of depressive symptoms was associated with an odds ratio of 5.87 (95% confidence interval [CI], 3.01 - 11.44) of being KOAS-positive, the authors report. "However, the influence of a depressive disorder was limited to subjects with a radiographic severity of minimal to moderate; the odds ratio for the presence of a depressive disorder was 2.97 (95% CI, 1.04 to 8.47) in patients with a Kellgren-Lawrence grade [a measure of radiographic severity] of 0 or 1, and 72.08 (95% CI, 8.88 to 584.77) in those with a Kellgren-Lawrence grade of 2 or 3." Depressive disorders were not associated with an increased risk of being KOAS-positive in participants with a Kellgren-Lawrence grade of 4.
"Our findings support the hypothesis that comorbid depression explains the discordance between radiographic severity and symptomatic severity," Dr. Kim said.
"Depression is common in patients with arthritis, and much more prevalent than in the general population," said Mary Margaretten, MD, assistant professor of medicine in the Division of Rheumatology at the University of California–San Francisco.
"It is surprising that more severe [KOA] is not associated with depression, but perhaps patients with severe radiographic [KOA] have developed coping mechanisms over time that the patients with more mild and recent arthritis have not yet learned."
"The relationship between arthritis and depression can certainly go both ways," said Dr. Margaretten, who was not involved in this study.
"The pain and disability associated with arthritis can contribute to depressive symptoms, and just as possible, depression can contribute to a patient's perception of pain." She warned that "since this is a cross-sectional study, causality between depression and knee pain from arthritis cannot be determined."
Clinicians should suspect comorbid depression in patients with KOA whenever the symptoms seem unaccountably severe or persistent, especially when the arthritis is mild to moderate, Dr. Kim concluded. "For those patients, screening for the presence of comorbid depression or consultation with a psychiatrist to determine optimal treatment should be considered."
This study was supported by grants from Pfizer Global Pharmaceuticals and Seongnam City Government in Korea. One or more authors received funding support from Pfizer Global Pharmaceuticals and from the Seongnam City Government in Korea. Dr. Margaretten has disclosed no relevant financial relationships.
J Bone Joint Surg. 2011;93:556-563. Abstract
Clinical Context
KOA is a common cause of impairment and disability, and the prevalence increases with age and is expected to further increase in the coming years. Depression is also highly prevalent and contributes further to knee pain in osteoarthritis, but few studies have examined the association between KOA severity by radiographic assessment, symptoms, and depression, and how these factors are related.
This is a population-based prospective cohort study conducted in Korea within the Korean Longitudinal Study on Health and Aging to examine the association between KOA severity by radiographic assessment, clinical assessment, and depression.
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