Abstract 2077: Strong Association of Bone Marrow Lesions and Effusion with Pain in Osteoarthritis
Alan Baer, M.D.
Authors:
G. Lo1, T. McAlindon1, J. Niu2, Y. Zhang2, C. Beals3, C. Dabrowski4, M. Hellio5, M. Luchi6, D. Hunter2.
Background:
Degeneration of the articular cartilage is the prinicipal pathologic abnormality in patients with osteoarthritis. Since the cartilage is aneural, the pain of osteoarthritis must originate in other joint structures. With MR imaging, it is now possible to identify and quantify at least three of these potential sources of pain: the presence of a joint effusion (potentially leading to painful distention of the joint capsule or the formation of popliteal cysts), synovitis (associated with low-grade inflammation) and bone marrow lesions (BML). The latter appear as hyperintense signals on fat-suppressed T2 MR imaging and correlate with a variety of pathologic findings in the bone, including bone marrow necrosis, fibrosis, edema, or bleeding as well as areas of abnormal trabeculae. Since these bone marrow lesions correlate with the presence of pain in OA and are associated with more rapid progression of the disease, they are felt to reflect pathologic changes induced by the OA process in the subchondral bone. Previous studies have examined each of these structural lesions as causes of pain in OA of the knee, but few have looked at these multiple abnormalities simultaneously. This study was performed to test whether bone marrow lesions, synovitis, and effusion are each independently associated with pain in OA of the knee.
Methods
This was a cross-sectional study of people with symptomatic knee OA, with the patient sample being derived from the Osteoarthritis Initiative (OAI), a nationwide study of the natural history of knee OA. One knee MRI from each participant was scored for BMLs, synovitis, and effusion. A different MRI reader scored the MRI for the presence of a joint effusion and for synovitis. Knee pain was defined as moderate-to-extreme pain (score of 2-4) on any of the 3 Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index questions that assess weight-bearing pain.Univariate and multivariate analyses were performed to determine the association of BMLs, effusion, and synovitis with knee pain.
Results
The participants (N=160) had a mean age of 61 years, mean BMI of 30.3 and 50% were female.
|
Prevalence of mod-extreme pain |
Univariate Analysis |
Multivariate Analysis |
Max BML Score |
|
|
|
0 |
4/14 (28.6%) |
Referent |
Referent |
1 |
18/47 (38.3%) |
1.6 (0.4 - 5.7) |
1.3 (0.3 - 5.3) |
2 |
22/36 (61.1%) |
3.9 (1.0 - 15.0) |
3.3 (0.8 - 13.8) |
3 |
42/63 (66.7%) |
5.0 (1.4 - 17.8) |
3.9 (1.0 - 15.0) |
|
|
p for trend = 0.0006 |
p for trend = 0.005 |
Effusion Score |
|
|
|
0 |
7/26 (26.9%) |
Referent |
Referent |
1 |
30/62 (48.8%) |
2.5 (0.9 - 6.9) |
2.3 (0.8 - 6.6) |
2 |
35/55 (63.6%) |
4.8 (1.7 - 13.3) |
3.7 (1.3 - 10.7) |
3 |
14/17 (82.4%) |
12.7 (2.8 - 57.8) |
9.7 (2.0 - 46.7) |
|
|
p for trend = 0.0001 |
p for trend = 0.001 |
Synovitis Score |
|
|
|
0 |
2/7 (28.6%) |
Referent |
Referent |
1 |
42/79 (53.2%) |
2.8 (0.5 - 15.5) |
1.7 (0.3 - 11.1) |
2 |
29/54 (53.7%) |
2.9 (0.5 - 16.3) |
1.9 (0.3 - 12.4) |
3 |
13/20 (65%) |
4.6 (0.7 - 30.4) |
3.7 (0.5 - 29.1) |
|
|
p for trend = 0.20 |
p for trend = 0.30 |
Conclusions:
In a cross-sectional sample of people with symptomatic knee OA, pain was strongly associated with the presence of BMLs and a joint effusion, but not with synovitis. The strength of the association persisted when mutually adjusting for the other features, suggesting that each feature was independently associated with pain and supporting the idea that pain in OA is multifactorial.
Editorial Comment:
This study demonstrates that bone marrow lesions and the presence of a joint effusion are each independently associated with pain in OA of the knees. Thus pain in osteoarthritis is derived from multiple sources and may be amenable to targeted therapies. Similar analyses need to be done for other potential sources of pain, including full thickness cartilage defects with adjacent subchondral cortical bone defects, bursitis, and tendonitis.
