"These factors help to identify the knees more likely to progress."—Leena Sharma, MD
"These factors help to identify the knees more likely to progress," said lead researcher Leena Sharma, MD, of the arthritis division at Northwestern University's Feinberg School of Medicine in Chicago, Illinois.Quantitative cartilage loss outcome measures more sensitive
Researchers at Northwestern University and Salzburg University in Austria applied quantitative measures of cartilage loss and a cartilage integrity score to 251 osteoarthritic knees in 153 women and men with radiographic evidence of knee OA. They found that both medial and lateral meniscal damage as well as varus malalignment of the knee joint all affected progression of knee OA. The quantitative cartilage loss outcome measures were more sensitive than previously applied qualitative approaches.
Participants had a mean age of 66 years and a mean body mass index 30. Researchers scanned the knees with magnetic resonance imaging and graded meniscal damage and meniscal extrusion with Whole-Organ MRI Score. Varus-valgus alignment and medial-lateral laxity were also measured, and other local factors were adjusted in the statistical models, which had not been done in previous studies.
Cartilage volume, percentage of subchondral bone covered with cartilage, exposed subchondral bone area, and average thickness of cartilage were measured using specialized software that focused separately on medial and lateral segments of tibial and weightbearing femur cartilage of the knee joint. The researchers also scored cartilage integrity. They repeated the entire process 2 years later.
Medial meniscal damage significantly increased the likelihood of cartilage volume loss, cartilage thickness decrease, and denuded bone increase in both the medial tibial and the medial weightbearing femoral segments, the study found. Similarly, lateral meniscal damage predicted quantitative cartilage loss in both the lateral tibial and the lateral weightbearing femoral segments. Varus malalignment was strongly associated with cartilage loss from each medial surface. By contrast, valgus malalignment was not associated with lateral surface loss. Meniscal extrusion and joint laxity had inconsistent effects, and there was no significant relationship with outcome detected for either meniscal damage or malalignment with the qualitative cartilage assessment.
Translating research into practice
"There are noninvasive interventions to help counteract the load imbalance present in varus malaligned knees, such as lateral wedge insoles," Dr. Sharma told MSKreport. com. "At present, it is not clear if interventions such as these modify disease course, [but] our results support further development and trials of interventions. If they are able to improve long-term load distribution, then, in theory, they could inhibit the vicious circle of varus malalignment and OA disease progression."
The results also suggest a key role of meniscal damage in disease progression. "This is a tough issue as treatment for meniscal tears involves arthroscopic surgery," she said. "How best to treat meniscal tears in the setting of OA is a complex issue, but deserving of attention."
References
1. Sharma L, Eckstein F, Song J, et al. Relationship of meniscal damage, meniscal extrusion, malalignment, and joint laxity to subsequent cartilage loss in osteoarthritis knees. Arthritis Rheum. 2008; 58:1716-1726.
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