Layer-specific femorotibial cartilage T2 relaxation time in knees with and without early knee osteoarthritis: Data from the Osteoarthritis Initiative (OAI)

Magnetic resonance imaging (MRI)-based spin-spin relaxation time (T2) mapping has been shown to be associated with cartilage matrix composition (hydration, collagen content & orientation). To determine the impact of early radiographic knee osteoarthritis (ROA) and ROA risk factors on femorotibial cartilage composition, we studied baseline values and one-year change in superficial and deep cartilage T2 layers in 60 subjects (age 60.6 +/- 9.6 y; BMI 27.8 +/- 4.8) with definite osteophytes in one knee (earlyROA, n = 32) and with ROA risk factors in the contralateral knee (riskROA, n = 28), and 89 healthy subjects (age 55.0 +/- 7.5 y; BMI 24.4 +/- 3.1) without signs or risk factors of ROA. Baseline T2 did not differ significantly between earlyROA and riskROA knees in the superficial (48.0 +/- 3.5 ms vs. 48.1 +/- 3.1 ms) or the deep layer (37.3 +/- 2.5 ms vs. 37.3 +/- 1.8 ms). However, healthy knees showed significantly lower superficial layer T2 (45.4 +/- 2.3 ms) than earlyROA or riskROA knees (p <= 0.001) and significantly lower deep layer T2 (35.8 +/- 1.8 ms) than riskROA knees (p = 0.006). Significant longitudinal change in T2 (superficial: 0.5 +/- 1.4 ms; deep: 0.8 +/- 1.3 ms) was only detected in healthy knees. These results do not suggest an association of early ROA (osteophytes) with cartilage composition, as assessed by T2 mapping, whereas cartilage composition was observed to differ between knees with and without ROA risk factors.