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Abstract: Purpose: To study if the pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance (DCE-MR) images of the patellar cartilage are influenced by the main magnetic field strength. Materials and methods: DCE-MR images of the knee were obtained from 16 normal male subjects (eight cases in each 1.5 and 3T magnets). Also, four volunteers were evaluated in both equipments within 1 week. Cartilage pharmacokinetic parameters of vascular permeability (K trans), extraction ratio (k ep), extravascular extracellular space volume fraction () and intravascular space volume fraction () were obtained. Results: Statistically significant differences were observed between the 1.5 and 3T groups for K trans (mean±S.D.; 5.44±2.27 vs. 1.01±0.41, respectively) and (3.37±2.32 vs. 0.81±0.80). A difference in K trans was also present when the same controls were evaluated in both equipments. There were no significant differences for k ep and values. Reproducibility of the pharmacokinetic calculations, assessed with the 24 acquisitions, showed a very low test–retest root mean square coefficient of variation (0.13, 0.10, 0.23 and 0.18 for K trans, k ep, and , respectively). Conclusion: Cartilage vascular permeability values are influenced by the MR field strength. This should be taken in consideration when analyzing this biomarker. [Copyright &y& Elsevier]

Abstract: The radiological assessment and classification of bone bruising are reviewed. Most of the literature relates to the knee and the effect of various injuries and their pattern of bone bruising is reviewed. The natural history of bone bruising and biochemical changes are also considered. [Copyright &y& Elsevier]

Abstract: Our objective was to compare relaxation effects, dynamics and spatial distributions of ionic and non-ionic contrast agents in articular cartilage at concentrations typically used for direct MR arthrography at 1.5T. Dynamic MR-studies over 11h were performed in 15 bovine patella specimens. For each of the contrast agents gadopentetate dimeglumine, gadobenate dimeglumine, gadoteridol and mangafodipir trinatrium three patellae were placed in 2.5mmol/L contrast solution. Simultaneous measurements of T 1 and T 2 were performed every 30min using a high-spatial-resolution “MIX”-sequence. T 1, T 2 and ΔR 1, ΔR 2 profile plots across cartilage thickness were calculated to demonstrate the spatial and temporal distributions. The charge is one of the main factors which controls the amount of the contrast media diffusing into intact cartilage, but independent of the charge, the spatial distribution across cartilage thickness remains highly inhomogeneous even after 11h of diffusion. The absolute ΔR 2-effect in cartilage is at least as large as the ΔR 1-effect for all contrast agents. Maximum changes were 5–12s−1 for ΔR 1 and 8–15s−1 for ΔR 2. This study indicates that for morphologically intact cartilage only the amount of contrast agents within cartilage is determined by the charge but not the spatial distribution across cartilage thickness. In addition, ΔR 2 can be considered for quantification of contrast agent concentrations, since it is of the same magnitude and less time consuming to measure than ΔR 1. [Copyright &y& Elsevier]

Abstract: In an observational study, the validity and reliability of magnetic resonance imaging (MRI) for the assessment of autologous chondrocyte transplantation (ACT) in the knee joint was determined. Two years after implantation, high-resolution MRI was used to analyze the repair tissue with nine pertinent variables. A complete filling of the defect was found in 61.5%, and a complete integration of the border zone to the adjacent cartilage in 76.9%. An intact subchondral lamina was present in 84.6% and an intact subchondral bone was present in 61.5%. Isointense signal intensities of the repair tissue compared to the adjacent native cartilage were seen in 92.3%. To evaluate interobserver variability, a reliability analysis with the determination of the intraclass correlation coefficient (ICC) was calculated. An “almost perfect” agreement, with an ICC value >0.81, was calculated in 8 of 9 variables. The clinical outcome after 2 years showed the visual analog score (VAS) at 2.62 (S.D. ±0.65). The values for the knee injury and osteoarthritis outcome score (KOOS) subgroups were 68.29 (±23.90) for pain, 62.09 (±14.62) for symptoms, 75.45 (±21.91) for ADL function, 52.69 (±28.77) for sport and 70.19 (±22.41) for knee-related quality of life. The clinical scores were correlated with the MRI variables. A statistically significant correlation was found for the variables “filling of the defect,” “structure of the repair tissue,” “changes in the subchondral bone,” and “signal intensities of the repair issue”. High resolution MRI and well-defined MRI variables are a reliable, reproducible and accurate tool for assessing cartilage repair tissue. [Copyright &y& Elsevier]

Abstract: Articular cartilage abnormalities of the knee are a cause of significant patient morbidity. Several surgical techniques have been developed to treat these lesions to improve patient symptoms and to delay or prevent the development of osteoarthritis. MRI has been shown to be an accurate non-invasive test for the evaluation of articular cartilage injuries and for evaluating the postoperative knee following chondral repair. As these surgical repair techniques become more commonly performed, is important for radiologists to be familiar with the surgical techniques and the MRI appearance of the postoperative knee including both normal and abnormal findings. In this article, these chondral repair techniques will be reviewed as well those normal and abnormal MRI findings following these surgeries. [Copyright &y& Elsevier]

Abstract: Disorders of the anterior knee are common and include patellofemoral syndrome, patella instability, patella fracture, and patellar and quadriceps tendon ruptures. Depending on the operative procedure performed, the post-operative imaging appearance of these knees may be confusing. It is crucial for the radiologist to be familiar with the procedures performed in order to recognize the postoperative findings. Radiologists must be able to interpret hardware (anchors, screw and wires) and disruptions in soft tissue planes that may persist with these types of procedures. [Copyright &y& Elsevier]

Abstract: Considerable developments have occurred in meniscal surgery, and consequently in the imaging of post-operative menisci, over the last 15 years. A drive to preserve meniscal physiologic function for as long as possible, in order to delay osteoarthrosis, has resulted in limited partial meniscectomies, meniscal repairs and meniscal transplants. Each of these techniques affects the imaging appearance of the meniscus, reducing the accuracy of conventional MRI in predicting recurrent tears. The specificity of conventional MRI can be improved by employing at least two T2-weighted sequences, but this still leaves a shortfall in sensitivity. In an attempt to increase the diagnostic accuracy of cross-sectional imaging, MR arthrography (MRA) and CT arthrography (CTA), have been applied to the post-operative meniscus. Sensitivities and specificities for these two techniques approach 90% in predicting recurrent meniscal tears. In the setting of clinical symptoms and gross meniscal deficiency, meniscal allografts are being transplanted with increasing frequency. In these transplants meniscal degeneration, fragmentation and separation are common findings, but the role of imaging in the management of these patients has not yet been well defined. This review explores the imaging techniques available for the evaluation of the post-operative meniscus, their strengths and weaknesses, and the reasons that they may find a place in a rational strategy for imaging of the symptomatic post-operative knee. [Copyright &y& Elsevier]

Abstract: Until the advent of magnetic resonance imaging (MRI), evaluation of ligament reconstruction of the knee was largely based on clinical examination and radiographs. MRI is the modality of choice for noninvasive evaluation of reconstructed ligaments, menisco-capsular structures and soft tissues. This article reviews the surgical techniques, normal and abnormal appearances of the ACL and PCL grafts and common complications following ligament reconstruction. [Copyright &y& Elsevier]

Abstract: Knee replacement surgery, either with unicompartmental or total systems, is common. The purpose of this manuscript is to review the appearance of normal knee arthroplasty and the appearances of complications such as infection, polyethylene wear, aseptic loosening and particle-induced osteolysis, patellofemoral abnormalities, axial instability, and periprosthetic and component fracture. Knowledge of the potential complications and their imaging appearances will help the radiologist in the diagnostic evaluation of the patient with a painful knee arthroplasty. [Copyright &y& Elsevier]