Background Osteoarthritis (OA) is a heterogeneous disease characterized by joint degeneration including the progressive loss of hyaline articular cartilage. One of the challenges in diagnosis and management of OA is the insidious onset of gross morphological radiographic changes that often occur late in the disease process. Previous studies have demonstrated that cartilage transverse relaxation time (T2) mapping signified degenerative changes in the collagen content and mobility of water in the extracellular matrix. Recently, many have speculated that injury to the meniscus may play a key role in the initiation of OA.
Objectives The purpose of this study was to investigate the association of meniscal degeneration/injury observed on MRI with cartilage degeneration demonstrated on T2 mapping in knees without radiographic change.
Methods The study population consisted initially of 209 consecutive individuals with knee pain who underwent knee MRI examination at our institutions. Exclusion criteria was defined as inflammatory arthritis, osteonecrosis, osteochondritis dissecans, tumor, full thickness ligament tears, previous knee surgery, and OA with evident radiographic changes (Kellgren-Lawrence (KL) grade 2∼4). After applying these exclusion criteria, our study included 87 subjects (mean age: 47.5 years old). All MR examinations were performed using a 3.0T MR unit (Achieva 3.0T, Philips healthcare). Coronal images were acquired based on 2D T2-weighted turbo spin echo for T2 analysis. After the direct segmentation by referring to the fat-suppressed T2-weighted images (T2-FFE), 12 regions of interest (ROIs) were manually drawn on the surface layer of the cartilage on mid- coronal images of the femorotibial (FT) joints. Two musculoskeletal radiologists systemically evaluated T2 values of 12 ROIs. Meniscal lesions were graded using a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) of the knee. In addition, radial meniscal tears by discontinuity of the bandlike hypointensity on coronal images and white meniscus sign by sagittal fat-suppressed images were recorded. Logistic regression analysis was performed.
Results The WORMS scores of the posterior horn of the medial meniscus were not associated with the T2 values of the medial FT cartilage, however, radial posterior horn tear and white meniscus sign were associated with T2 values of medial and lateral FT cartilage (P<0.05, for 4 ROIs on the medial FT, and 1 ROI on the lateral FT). The multiple regression analysis adjusted by age and KL grades revealed white meniscus sign to be an independent factor increasing T2 values of the cartilage.
Conclusions Recent studies showed that medial posterior meniscal horn tear caused increased peak contact pressure in the medial compartment. The normal posterior horn of the medial meniscus appears as an image of low intensity triangle of the sagittal MRI of medial slice close to the posterior cruciate ligament. On the contrary, the image of the radial tear of posterior horn shows a high intensity triangle, so we refer to this feature as white meniscus sign, which is a convenient finding on routine clinical sequenced MRI. This study demonstrated that cartilage degeneration is highly associated with medial posterior meniscal horn tear at the time of earliest radiographic OA.
Disclosure of Interest : None declared