Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Malalignment of the Knee Is Associated with an Increased Risk for Incident and Enlarging Subchondral Bone Marrow Lesions in the More Loaded Compartments: The MOST Study.

Hayashi3,  Daichi, Englund5,  Martin, Roemer4,  Frank, Niu1,  Jingbo, Sharma6,  Leena, Segal9,  Neil, Lewis8,  Cora

Boston University, Boston, MA
Boston University School of Medicine, Boston, MA
Boston University School of Medicine, Boston, MA
Boston University School of Medicine
Lund University, Sweden
Northwestern University, Chicago, IL
UCSF, San Francisco, CA
University of Alabama at Birmingham
University of Iowa

Purpose:

Malalignment of the lower limb influences the load distribution across the articular surfaces of the knee joint. We hypothesized that subchondral bone marrow lesions (BML) result from increased mechanical loading. The aim of this study was to assess if malalignment is associated with incident and enlarging BML in the more loaded compartments of the tibiofemoral (TF) joint.

Methods:

The Multicenter Osteoarthritis Study (MOST) is an NIH-funded longitudinal observational study of individuals who have or are at high risk for knee OA. Full limb radiographs of both legs were taken at baseline and hip-knee-ankle mechanical axis was measured (varus <179°, neutral 179–181° and valgus >181°). MRI was performed on a 1.0T extremity system. MR images were assessed semiquantitatively in known order using the WORMS system. BML was scored on a 0–3 scale at baseline and at 30 months in 5 TF regions of the medial and lateral compartment, respectively. Outcome was defined as any increase in BML score, including within-grade change not fulfilling the criteria of a full-grade change. Relative risk of an increase in BML score in the medial and lateral compartments in relation to malalignment was estimated using a log linear regression model with the Poisson assumption. Adjustments were made for age, sex, body mass index and physical activity level. We also combined analyses for the more loaded compartments (i.e. medial BML in varus + lateral BML in valgus knees). In secondary analyses results were stratified by ipsilateral meniscal and cartilage status at baseline (i.e. no meniscal or cartilage pathology; meniscal damage present; cartilage loss present; both meniscal and cartilage pathology present) and also by compartments with or without pre-existing BML (i.e. 'incident' if no BML at baseline or 'enlarging' if pre-existing BML).

Results:

1,782 knees from 1,338 subjects were included (62% women, mean age 62.2±7.9 years, mean BMI 29.9±4.8 kg/m2). Compared to neutral alignment, baseline varus alignment was associated with increased BML scores in the medial compartment (adjusted RRs [95%CI] 1.8 [1.5–2.3]) and valgus alignment with BML score increases in the lateral compartment (2.4 [1.7–3.4]). Increase in BML score was more likely in the more loaded compartments (2.2 [1.8–2.6]) in malaligned knees compared to neutral knees. After stratification, this association remained in knees with ipsilateral meniscus damage (4.9 [1.1–22.6]), cartilage loss (1.4 [1.1–2.0]), or both (1.6 [1.2–2.0]) but not in knees without any ipsilateral meniscal or cartilage pathology (1.8 [0.9–3.4]). Both incident BML (1.8 [1.4–2.4]) and enlarging BML (1.8 [1.4–2.3]) were more likely to occur in the more loaded compartments in malaligned knees compared to neutral knees.

Conclusion:

Knee malalignment is associated with increased risk of incident and enlarging BMLs in the more loaded compartments of the TF joint over 30 months. Further longitudinal studies are needed to explore whether malalignment is a primary trigger of structural damage or a secondary phenomenon due to underlying structural damage. BML may be a marker of increased mechanical load experienced by overlying cartilage in a compartment-specific manner.

To cite this abstract, please use the following information:
Hayashi, Daichi, Englund, Martin, Roemer, Frank, Niu, Jingbo, Sharma, Leena, Segal, Neil, et al; Malalignment of the Knee Is Associated with an Increased Risk for Incident and Enlarging Subchondral Bone Marrow Lesions in the More Loaded Compartments: The MOST Study. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :131
DOI: 10.1002/art.27900

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