What is pain, and how much is too much?
Patients with painful hip or knee osteoarthritis say they know how much pain they should have to make joint replacement surgery necessary, and that their physicians are largely in the dark about their pain. Patients use the Supreme Court’s famous approach to identifying pain that warrants knee surgery: I know it when I feel it.
To get the perspective of osteoarthritis patients, Dr. Gillian Hawker, a Toronto rheumatologist, and her associates put 58 local patients with moderately severe hip or knee osteoarthritis in focus groups, including 36 veterans of total joint replacement surgery. They discussed joint surgery appropriateness, and the point when appropriateness and their willingness to have the surgery intersect. The major determinant was their pain: their ability to cope with it, and its impact on their quality of life.
Patients “evaluated their pain against some invisible marker,” and despite having what they called high levels of pain they often said it was not bad enough to justify surgery, Dr. Hawker reported last month at the World Congress on Osteoarthritis. As one focus-group patient put it, “I don’t feel I’m ready.” But when their pain became bad enough, they said it trumped all other considerations of whether or not to have joint surgery. Most patients in the focus groups also said their pain had been “inadequately evaluated” by their physicians.
Other study results reported at the Congress also highlighted the highly subjective and variable nature of knee pain. Dr. Tuhina Neogi from Boston University measured central sensitization in knee osteoarthritis patients, and saw that both increased disease severity and duration significantly boosted the incidence of central sensitization, a neurologic process that alters the nervous system and potentially increases pain sensitivity.
Dr. Neogi and her associates found the only way to reliably measure central sensitization was by comparing pain in a patient’s knee affected by osteoarthritis and in the patient’s second, unaffected knee. Comparisons between different patients involved too much variable noise to show a significant link between osteoarthritis and central sensitization. Comparing knees within individual patients cut away the effects of genetics, and psychosocial and cultural factors, allowing each patient to apply their own unique, personal criteria for judging pain severity.
—Mitchel Zoler (on Twitter @mitchelzoler)