Meniscal tears are a common indication for arthroscopic knee surgery. The blood supply of meniscus is an essential indicator for the prognosis of meniscal problems. The tears in the vascular zone of the meniscus are far more likely to heal than tears in the avascular zone of the meniscus [1, 2]. With a favorable blood supply of the teared meniscus, it’s tend to preserve the meniscus as much as possible at partial meniscetomy and meniscal repair. Although the conventional MR sequences is used as a mainly effective way to evaluate the meniscal lesions, it is hard to provide the vascular supply status of the teared meniscus. Intravoxel incoherent motion (IVIM) theory provide information about microcirculation of blood in addition to the pure molecular diffusion [3]. The perfusion information detected with IVIM is emphasized on microvascular bed, which is the typical blood supply pattern of meniscus. In this study, reduced FOV DWI technology and IVIM model were used to estimate the change of vasculature in normal, degenerated and teared meniscus.Fifty patients with knee problems were recruited in this study (age range 23-67, M/F 25/25). The menisci were imaged in sagittal plane, and only the posterior horn of the medial menisci (PMM) was counted in this study for the highest prevalence of tears occurred in PMM. The menisci were further divided in 3 groups (normal, degenerated and teared group) according to the five-step meniscal scoring scheme of MRI by conventional PDWI sequence. Data were acquired on a 3.0 Tesla system (GE MR 750, GE Healthcare) with an 8 HD knee coil using a reduced FOV (rFOV) diffusion-weighted spin-echo EPI pulse sequence with the following parameters: TR/TE=3500/minimum ms, acceleration factor 2, slice thickness 4 mm with 0.5mm gap and FOV 180×90, matrix size 180×90 to maintain a 1×1 mm in plane resolution. For each subject, multiple b values (0, 20, 50, 80, 100, 120, 150, 180, 200, 300, 400 sec/mm2) in three orthogonal directions were acquired. The perfusion fraction f, pseudodiffusion coefficient D* and diffusion coefficient D were calculated from IVIM sequence using a bi-exponential model. The parameters of the menisci located in red zone were measured in each specimen for the vasculature only exist in the red zone of meniscus. The ROIs drew in the red zone contained 30% of the meniscal width from the peripheral border in consecutive sagittal planes. Each observation was averaged in every sagittal plane which contains the wedge-shaped meniscus. The values of f, D* and D in the red zone of PMM among the normal, degenerated and teared meniscus groups were analyzed by one-way ANOVA. Further pairwise comparisons were performed between each two group. SPSS 19.0 was used.Among the 50 PMMs, 35 normal menisci, 8 degenerative changes and 7 meniscal tears were confirmed by PDWI sequence. In comparison of f among the 3 groups of red zone of PMM showed a significant difference (P = 0.043) by one-way ANOVA. In further pairwise comparison, a significant reduction of f value (P = 0.013) was observed in red zone of teared meniscus compared with the normal subjects (Figure 1 to 3). No significant differences were derived between normal and degenerative groups and between degenerative and teared groups. The other IVIM parameters of D* and D didn’t show significant difference in red zone of PMM among the 3 groups.The blood supply to the meniscus originates from a network of arborizing vessels within the peripheral capsular and synovial attachments. This perimeniscal capillary plexus give rise to radial branches penetrating the periphery of the meniscus [4]. The microcirculation may changes along with aging, progression of degeneration or occurrence of tears. In addition, blood supply is a crucial factor in determining the treatment and prognosis of meniscal tears. The pseudodiffusion D* describes the incoherent movement of water in the microvasculature compartment and negatively correlates with the classical perfusion parameter mean transit time (MTT) [5,6]. The perfusion fraction f is the volume fraction of water flowing in capillary compartment and correlates with the classical perfusion parameter blood volume (BV). The significant reduction of f value in red zone of teared meniscus reflects a process of diminishing in amount of blood volume of meniscus with tears. The results of this study are preliminary but encouraging. The IVIM profusion fraction f could detect the microvascular supply of the meniscus and may be a potential predictor for prognosis of meniscal tears.