Depression may make the pain of knee arthritis worse, a new study says.
The findings may explain some why some patients with this condition report experiencing a high level of pain, even though their X-rays indicate otherwise.
"The results of this study indicate that depression can play a major role in the way patients experience the symptoms of knee arthritis, and that even when X-rays show the arthritis is not severe, patients with depression may report significant pain," said study researcher Dr. Tae Kyun Kim, director of the Division of Knee Surgery and Sports Medicine at Seoul National University Bundang Hospital's Joint Reconstruction Center.
Knee arthritis, or knee osteoarthritis, is a form of arthritis in which the cartilage in the knee joint breaks down, leading to bone rubbing on bone. It typically affects men and women over 50 years of age, and occurs most frequently in people who are obese. Symptoms can include pain or stiffness in or around the knee, swelling of the knee and limited range of motion when walking or moving the knee.
The study included 660 men and women aged 65 years or older living in Seongnam, South Korea. Participants were evaluated for the severity of their knee arthritis using X-rays. Interviews and questionnaires were used to assess whether patients suffered from depressive disorders.
As expected, the researchers found the levels of pain attributed to knee arthritis were higher in patients whose X-rays indicated greater joint damage. But they also found depressive disorders were associated with an increase in pain in patients with mild to moderate knee arthritis, even when X-rays did not show significant joint damage.
"When evaluating the results of this study, the contribution of depression to knee osteoarthritis symptoms was almost as important as the damage indicated on X-rays," Kim said.
The link may explain why some patients continue to experience chronic pain even after they have had knee replacement surgery.
"Although some poor outcomes after [knee replacement surgery] are undoubtedly due to surgical technique and implant factors, much of the pain and disability after surgery is medically unexplained," the researchers write in the Journal of Bone and Joint Surgery, where the study was published.
"Despite the reported satisfactory outcomes of knee replacement surgery, a percentage of patients still experience knee pain and impaired movement," Kim said. "Sometimes pain and disability after surgery is medically unexplained, so in these patients screening for depression might be a very good option."
However, further work needs to be done to tease out the exact cause-effect relationship between depression and knee arthritis, the researchers say.
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