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Measurement of T(2) and T(1)ρ relaxation time is a quantitative evaluation technique that uses magnetic resonance imaging. This study aimed to evaluate T(2) and T(1)ρ relaxation time considering the load on the knee. 14 healthy volunteers were studied at 3 T. Four main compartments were defined for cartilage analysis in the knee joint: lateral femoral condyle (LFC), medial femoral condyle (MFC), and lateral and medial tibia (LT and MT). Femur cartilage was partitioned into anterior, middle, and posterior nonweight-bearing (a-NWB, m-NWB, p-NWB) portions and weight-bearing (WB) portions. T(2) and T(1)ρ values between the medial side and lateral side indicated a nonsignificant difference. T(2) and T(1)ρ values of NWB portions were higher than those of WB portions. The measured value rate of extension of NWB to WB was more remarkable in the T(1)ρ value than in the T(2) value. Therefore, evaluating cartilaginous injuries and damages using the T(1)ρ value seems to more effectively describe them.

Fat-suppressed three-dimensional coherent oscillatory state acquisition for the manipulation of image contrast (3D-COSMIC) is a sequence that is based on fast imaging employing steady state acquisition (FIESTA) of balanced steady-state free precession (balanced SSFP). Since the data acquisition of steady-state transition is filled up with the center of k-space, improvement in the contrast of the cartilage, which is a low T₂/T₁ value domain, is expected. This time we report on the usability in applying the above sequence to cartilage imaging of the knee joint and comparing and examining this sequence with the sequence in the past from the viewpoints of the contrast and scan time. As a result, compared with fat-suppressed three-dimensional spoiled gradient echo (3D-SPGR), the contrast of marrow and synovial fluid was equivalent to that of the cartilage, and imaging time was shorter than half of that with the cartilage. Compared with a fat-suppressed two-dimensional proton density weighted image (2D-PDWI), the contrast of the cartilage and synovial fluid was significantly improved, and spatial resolution was also excellent. As a short imaging time and a high resolution image pick-up are possible for fat-suppressed 3D-COSMIC, and it can describe minute damage of the cartilage since it depicts synovial fluid as high-level signals, I think this technique is useful.

In the reconstructive procedure of the anterior cruciate ligament (ACL), the relationship was investigated between the orientation of the drill holes from the isometric points and the deformity in the ligament graft. We first investigated, by numerical analysis, the optimal orientation of the drill holes for minimal deformation. Secondly, we experimentally by using eight fresh cadaveric knees, measured the relationship between the orientation of the drill holes and the bending angle in the grafts. The optimal orientation of the drill hole in the femur was found to be tilted 20 degrees laterally in the coronal plane and 23 degrees anteriorly in the sagittal plane. In the tibia, the drill hole should be directed 24 degrees medially and 50 degrees anteriorly from the isometric point. The numerically analysed bending angle corresponded well to the results from the experimental study. The deformation in the graft on the femoral side was larger than that on the tibial side. Therefore, the orientation of the femoral drill hole was concluded to be more important than the orientation of the tibial drill hole.

To evaluate the diagnostic ability of MR imaging for plica synoviallis mediopatellaris (PSM), we retrospectively reviewed the MR imaging findings of patellofemoral space in 20 knee joints of 11 patients. In all 20 knee joints, arthroscopy and MR imaging were available. MR imaging was performed with a 1.5 Tesla Magnetom (Siemens) using a round surface coil. Pulse sequences were SE (TR 600 ms/TE 26 ms), SE (TR 200 ms/TE 26, 70 ms) and FLASH (TR 450 ms/TE 15 ms/FA 90 degrees). In six of the 20 knees with PSM proved by arthroscopy, a low intensity band was shown above the medial condyle of the femur on both T1- and T2-weighted MR images, and on FLASH images this band was shown as intermediate intensity. In the other 14 knees with no PSM observed by arthroscopy, the low intensity band was not shown on MR imaging. In all 20 knees, a similar low intensity band was shown about 1 cm cranial to the medial condyle of the femur. This should not be diagnosed as PSM. The low intensity band seen on T1- and T2-weighted MR images and its anatomical relation to the medial condyle are important in diagnosing PSM.

Knee motion in the full flexion range was measured for fourteen specimens under moderate load, and for eight normal volunteers while descending a step. Measurements showed that the posterior femoral condyles could be accurately modelled as parts of spheres. The line joining the centers of the spheres was defined as the femoral axis and joint motion was described by motion of this axis relative to axes defined on the tibial surface. From 0 to 120 degrees of flexion, the lateral center moved posteriorly by seventeen millimeters, the medical center moved forward by two millimeters, external rotation was 20 degrees, and varus-valgus rotation was 4 degrees. Specimens and volunteers gave similar results. The method was simple and accurate and has several potential applications.