Could knee pain in the elderly be due more to depression than to the physical symptoms of the disease? An investigation performed at Seoul National University Bundang Hospital in Seongnam, South Korea, and published in the March Journal of Bone and Joint Surgery suggests that this may be true, especially in those people with less radiographic evidence of knee osteoarthritis.

The information came to light as part of the Korean Longitudinal Study on Health and Aging (KLoSHA), a population-based prospective cohort study of health, aging, and common geriatric diseases.

One thousand elderly Koreans aged 65 or older participated in the study; 660 underwent a radiographic examination of their knee, symptom evaluation, and diagnostic interviews for depressive disorders. (Subjects who had already undergone total knee arthroplasty, those diagnosed with a major psychiatric disorder, and those with a neuromuscular disorder were excluded.)

Several grading systems and scales were used to evaluate KLoSHA participants for the severity of knee osteoarthritis and for depression. Blinded evaluations were performed of three knee radiographs using the Kellgren-Lawrence grading system. Symptom severity was evaluated on the basis of the Western Ontario and McMaster Universities Osteoarthritis Index, with symptomatic knee osteoarthritis defined as a score of 39 or higher.

Diagnostic interviews to assess for depressive disorders included the Korean version of the Mini-International Neuropsychiatric Interview and the Korean version of the Geriatric Depression Scale.

Discrepancies in the relationship between the degree of pain reported by patients and radiographic severity of joint osteoarthritis have frequently been reported, said the report's authors. They cited numerous shortcomings of previous studies, including few that have correlated radiographic findings with symptom severity, others that included multiple joints, and still others that may not have properly assessed the patellofemoral joint, possibly underestimating radiographic changes.

Unsophisticated methods of pain measurement also may have hindered evaluations in past studies, the researchers noted, and additional pain-related risk factors such as obesity may not have been considered.

The results of this study may explain why some patients appear to be in more pain than their radiographic findings would suggest.

Patients who exhibited minimal to moderate radiographic severity of knee osteoarthritis (Kellgren-Lawrence grade 0 to 3) and the presence of a depressive disorder had an increased likelihood of symptomatic knee osteoarthritis (pain, stiffness, and disability). The presence of a depressive disorder was not associated with the likelihood of symptomatic knee osteoarthritis in subjects with severe osteoarthritis (Kellgren-Lawrence grade 4).

"These findings suggest that depression contributes substantially to the discrepancy between symptoms and radiographic degenerative changes that have been observed in patients with knee osteoarthritis," said the researchers. "This bidirectional relationship between pain and depression suggests that both should be considered as simultaneous therapeutic targets during the management of patients with knee osteoarthritis. Assessment and management of coexisting depression should be integrated with the assessment and management of knee osteoarthritis, particularly when radiographic changes of osteoarthritis in the knee joint are not severe."

This study was supported by Pfizer Global Pharmaceuticals and Seongnam City Government in Korea.

An abstract of "Association Between Comorbid Depression and Osteoarthritis Symptom Severity in Patients With Knee Osteoarthritis" is posted at <www.ejbjs.org/cgi/content/abstract/93/6/556>.