SAN DIEGO – To at least some extent, findings seen on magnetic resonance imaging indicate the source of pain in osteoarthritic knees, according to University of Pittsburgh researchers.
Medial joint line knee pain, they found, is associated with bone marrow lesions in the medial compartment. Medial regional knee pain is associated with medial bone marrow lesions, meniscal extrusions, and meniscal damage, according to Dr. Kent Kwoh, a professor in the division of rheumatology and clinical immunology at the University of Pittsburgh.
"If you have pain on the inner side of your knee, and you’re biomechanically loading that side too much, you [know] that there’s pathology there."
There were trends, as well, including one toward lateral regional knee pain being associated with lateral meniscal extrusions, but they didn’t reach statistical significance, probably because of the small number of patients in the trial with lateral regional pain and other specific findings, he said.
Nonetheless, the findings mean that "the location of pain is where the pathology is. We haven’t known that. It’s an important observation," said Dr. David Felson after Dr. Kwoh’s presentation.
"If you have pain on the inner side of your knee, and you’re biomechanically loading that side too much, you [know] that there’s pathology there, and that you can diminish the pain and perhaps help the pathology by focusing on the biomechanical abnormalities," with bracing, wedging, or other targeted interventions, said Dr. Felson, a professor of medicine and epidemiology at Boston University. He also is director of the Research in Osteoarthritis in Manchester (ROAM) group the University of Manchester (England).
The 177 subjects in the study had mild to moderate pain on most days. Their age averaged 52 years, their mean body mass index was 29 kg/m2, and 46% were women. Half had medial joint space narrowing, and about 20% had lateral joint space narrowing. Slightly more than half had medial osteophytes, and slightly less than half had lateral osteophytes.
The Pittsburgh team used MRI to look at where patients said it hurt, or the general region if they could not point to the exact place.
The relative risk ratio for medial bone marrow lesions in the 83 patients with local medial joint line pain was 9.89. The risk ratios for medial bone marrow lesions, meniscal damage, and meniscal extrusion in the 36 patients with regional medial pain were 12.10, 3.72, and 8.77, respectively. The findings were statistically significant.
Right knee medial joint line pain and right knee lateral joint line pain with patellar and medial joint line components were the most common localizable pain types. Left knee patellar and left knee medial pain were the most common regional types.
The congress was sponsored by the Osteoarthritis Research Society International.
Dr. Kwoh and Dr. Felson said they have no disclosures. The University of Pittsburgh and Coca-Cola Co.’s Beverage Institute paid for the work.