Purpose to determine if asymmetry between hips in pain or radiographic osteoarthritis (RHOA) is associated with worse pain and joint space narrowing (JSN) at baseline and longitudinally in knees contralateral to more affected hips. Methods We studied 279 participants in the Osteoarthritis Initiative with baseline asymmetry between hips in pain and 483 with asymmetry in RHOA none of whom had a hip replacement for ≥4 years after baseline. RHOA assessed from pelvis radiographs was categorized as none, possible or definite and hip pain on most days of a month in the past year as present/absent. Knee pain (WOMAC scale) and JSN (fixed flexion radiographs) were categorized as none, mild and moderate-severe. We compared knees contralateral and ipsilateral to more affected hips on baseline knee pain and JSN using clustered multinomial regression and on change in knee pain and JSN over 4–5 years using generalized linear and logistic estimating equations. Results Knees contralateral to painful hips had less baseline pain (“moderate-severe” vs. “none”, relative risk ratio [RRR]: 0.39, 95% CI = 0.27–0.57), but greater baseline JSN (“moderate-severe” vs. “none”, RRR: 1.62, 95% CI = 1.09–2.38) and greater worsening of pain during follow-up (p = 0.001). Knees contralateral to hips with worse RHOA had nonsignificant trends for greater baseline JSN (p = 0.10) and JSN progression (p = 0.17). Conclusion These findings provide limited support for the hypothesis that early asymmetry in hip pain and RHOA is associated with worse pain and structural outcomes in knees contralateral to the more affected hip.

Objectives To investigate the change in cartilage T2-values and structural degeneration in knee joints over 72 months in women of African American (AA) vs. Caucasian American (CA) ethnicity. Methods Knee 3T MRIs from baseline, 24, 48 and 72 month visits of 100 AA and 100 CA women from the OAI were assessed for cartilage T2-values and whole-organ magnetic resonance imaging (WORMS) score. Subjects were pair-matched by age, BMI, Kellgren-Lawrence (KL) score, clinical site and subcohort within the OAI. We compared the rate of change in whole knee cartilage T2-values and WORMS cartilage, bone marrow edema pattern (BMEP) and meniscus scores between the two ethnic groups using mixed random effects models. Results At 24 and 48 months 60 subjects and at 72 months 45 subjects per group were available for analysis resulting in 38 complete pairs with data of all time points. Compared to CA, cartilage T2-values in AA increased at a significantly faster rate at baseline (AA: 0.45ms/y, CA: 0.35ms/y, p=0.029) and averaged over 6 years (AA: 0.36ms/y, CA: 0.27ms/y, p=0.039) with changes in both groups reaching a plateau by 48 months. Cartilage, meniscus and BMEP scores tended to increase in both groups during follow-up, but rates of change did not differ by ethnicity. Conclusion Cartilage T2-values increased faster over 72 months in AA than CA, however changes in WORMS cartilage, meniscus and BMEP scores did not differ. T2-values may be able to distinguish ethnicity-related differences of cartilage degeneration at an early stage before differences in structural joint degeneration appear.

Objective To determine whether knee cartilage composition differs between African-American and Caucasian-American women at risk for Osteoarthritis using in-vivo 3 Tesla MRI T2 relaxation time measurements. Methods Right knee MRI studies of 200 subjects (100 African-American women, and 100 closely matched Caucasian-American women) were selected from the Osteoarthritis Initiative. Knee cartilage was segmented in the patellar (PAT), medial and lateral femoral (MF/LF), and medial and lateral tibial compartments (MT/LT)). Mean T2 relaxation time values per compartment and per whole joint cartilage were generated and analyzed spatially via laminar and grey-level co-occurrence matrix texture methods. Presence and severity of cartilage lesions per compartment were graded using a modified WORMS grading. Statistical analysis employed paired t- and McNemar testing. Results While African-American women and Caucasian-Americans had similar WORMS cartilage lesion scores (p=0.970), African-Americans showed significantly lower mean T2 values (~1ms difference; ~0.5SD) than Caucasian-Americans in the whole knee cartilage (p<0.001), and in the subcompartments (LF: p=0.001, MF: p<0.001, LT: p=0.019, MT: p=0.001) and particularly in the superficial cartilage layer (whole cartilage: p<0.001, LF: p<0.001, MF: p<0.001, LT: p=0.003, MT: p<0.001). T2 texture parameters were also significantly lower in the whole joint cartilage of African-Americans than in Caucasian-Americans (variance: p=0.001; contrast: p=0.018). In analyses limited to matched pairs with no cartilage lesions in a given compartment, T2 values remained significantly lower in African-Americans. Conclusion Using T2 relaxation time as a biomarker for the cartilage collagen network, our findings suggest racial differences in the biochemical knee cartilage composition between African-American and Caucasian-American women.

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