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This article highlights five knee injuries that, in the author's experience, are commonly overlooked by readers inexperienced in knee MRI: ramp lesions, meniscocapsular tears, meniscal root ligament tears, posterior capsular ligament tears, and partial anterior cruciate ligament tears. Although these injuries are readily apparent when the images are assessed for the given abnormality, the author believes they may be overlooked because either the injury is not considered or the affected area is not closely inspected. These injuries may not alter immediate clinical management or require surgical intervention; nevertheless, they may result in patient symptoms and may potentially increase the risk of further knee injury. Moreover, these injuries are difficult to recognize clinically and arthroscopically. This review presents these five injuries, emphasizing relevant anatomy, normal MRI appearances, common injury patterns, and tips to avoid overlooking them. Routine review of these areas when interpreting knee MRI, with additional imaging as necessary, will allow these injuries to be recognized more regularly.

Please see the Editorial Comment by Derik L. Davis discussing this article. BACKGROUND. Potential approaches for abbreviated knee MRI, including prospective acceleration with deep learning, have ac...

The purpose of this study is to describe the MRI findings and treatment decisions and outcome for Morel-Lavallée lesions (MLLs) of the knee and to investigate whether evidence exists to support an increased frequency of such lesions on the medial or lateral side by performing a cadaveric experiment.In a 4-year period, 24 MRI studies of 24 consecutive patients (16 male patients and eight female patients) with knee MLLs were retrospectively reviewed. Patient demographic characteristics, treatment decisions and outcome, and associated injuries were recorded. The location of the MLL was categorized as medial, lateral, or global. Lesions were categorized according to an established MRI classification. During the cadaveric experiment, the compartmental pressures of the medial or lateral aspect of the knee were monitored in 20 cadaveric knees. The chi-square test, t test, and Pearson correlation were used for statistical analysis.MLLs were located medially in 16 patients, laterally in two patients, and globally in six patients. The medial location was significantly more common than a lateral or global location (p0.05). MLLs were classified as type I in 14 patients, type II in eight patients, and type III in two patients. MRI type was correlated with the chronicity of injury (rKnee MLLs have a predilection for the medial side, which may be attributed to the lower resistance in this location, and they have variable patterns on MRI, which correlate with chronicity. Conservative treatment of type I and II lesions seems effective.

OBJECTIVE. The purpose of this article is to review current and emerging techniques and strategies that can be used to accelerate acquisition times in routine knee MRI. CONCLUSION. Specific techniques reviewed include 3D fast spin-echo imaging as well as new approaches to rapid image acquisition techniques (parallel imaging, compressed sensing, simultaneous multislice, and neural network reconstruction techniques) and their potential application to knee MRI.

OBJECTIVE. A recent publication has drawn attention to the anterolateral ligament, a structure of the knee with which most radiologists are unfamiliar. We evaluate this structure on MRI; clarify its origin, insertion, meniscal relationship, and morphologic appearance; and identify its relationship with the Segond fracture. MATERIALS AND METHODS. A total of 53 routine knee MRI studies interpreted as normal were reviewed to characterize the anterolateral ligament. A further 20 knee MRI studies with a Segond fracture were assessed to determine a relationship between the fracture and the anterolateral ligament. RESULTS. In all 53 cases, a structure was present along the lateral knee connecting the distal femur to the proximal tibia, with meniscofemoral and meniscotibial components. This structure was somewhat ill defined and sheetlike, inseparable from the adjacent fibular collateral ligament proximally and iliotibial band distally. Aside from one case limited by anatomic distortion, all cases with a Segond fracture exhibited attachment of this structure to the fracture fragment (19/20 cases). CONCLUSION. An ill-defined sheetlike structure along the lateral knee exists attaching the distal femur, body of lateral meniscus, and proximal tibia. This structure has been referenced in the literature dating back to Paul Segond's original description of the Segond fracture in 1879. The structure is identifiable on MRI and appears to be attached to the Segond fracture fragment. For the radiologist, it may be best to forgo an attempt to separate this structure into discrete divisions, such as the anterolateral ligament, because these individual components are inseparable on routine MRI.

Patients with symptomatic Hoffa fat pad impingement often exhibit fat pad edema on MRI. We studied two patient groups to determine the association between MRI fat pad edema and clinical symptoms of Hoffa fat pad impingement.We studied 34 consecutive patients with an MRI diagnosis of fat pad edema and no injury in the prior year (group 1) and 47 consecutive patients with a knee MRI examination and no injury in the prior year (group 2). Two sports medicine physicians reviewed the clinical records to confirm or exclude symptomatic fat pad impingement. Two musculoskeletal radiologists independently scored 12 Hoffa fat pad locations for the presence of edema, noting the epicenter.Seventeen of the 34 patients in group 1 had clinical symptoms of fat pad impingement, with all 34 having fat pad edema. There was no association between clinical fat pad impingement and fat pad edema in any specific location (p0.183), but patients with fat pad impingement had a greater number of regions of edema (p = 0.005, 0.026 for two observers). In group 2, all four patients with clinical fat pad impingement had MRI fat pad edema, but 38 of the 43 patients without clinical impingement had MRI fat edema; 11 of the 38 had edema centered in the superolateral fat pad.Edema is present on MRI in the superolateral region of Hoffa fat pad in patients with clinical fat pad impingement. However, such edema can also be present in patients without symptoms of fat pad impingement.

OBJECTIVE. The goal of this article is to summarize the literature about the diagnosis of meniscal tears on MRI including the normal appearance of the meniscus and the appearance of the various types of meniscal tears. In addition, I discuss my experience with the causes of errors in the MR diagnosis of meniscal abnormalities and the nuances of meniscal abnormalities that can mimic a meniscal tear. CONCLUSION. MRI is a highly accurate imaging method for diagnosing meniscal tears. To avoid errors in diagnosing meniscal tears, those interpreting MR examinations of the knee need to be aware of the attachments of the menisci and the normal variations in meniscal anatomy that may resemble a meniscal tear. In addition, by being aware of the patterns of meniscal tears, it is easier to diagnose the less common tears.

The purpose of this investigation was to assess workflow for medical imaging studies, specifically comparing liver and knee MRI examinations by use of the Lean Six Sigma methodologic framework. The hypothesis tested was that the Lean Six Sigma framework can be used to quantify MRI workflow and to identify sources of inefficiency to target for sequence and protocol improvement.Audio-video interleave streams representing individual acquisitions were obtained with graphic user interface screen capture software in the examinations of 10 outpatients undergoing MRI of the liver and 10 outpatients undergoing MRI of the knee. With Lean Six Sigma methods, the audio-video streams were dissected into value-added time (true image data acquisition periods), business value-added time (time spent that provides no direct patient benefit but is requisite in the current system), and non-value-added time (scanner inactivity while awaiting manual input).For overall MRI table time, value-added time was 43.5% (range, 39.7-48.3%) of the time for liver examinations and 89.9% (range, 87.4-93.6%) for knee examinations. Business value-added time was 16.3% of the table time for the liver and 4.3% of the table time for the knee examinations. Non-value-added time was 40.2% of the overall table time for the liver and 5.8% for the knee examinations.Liver MRI examinations consume statistically significantly more non-value-added and business value-added times than do knee examinations, primarily because of respiratory command management and contrast administration. Workflow analyses and accepted inefficiency reduction frameworks can be applied with use of a graphic user interface screen capture program.

The purpose of our study was to illustrate the MRI features of meniscal flounce and the meniscal locations on the tibial plateau after positional changes without external force and to evaluate the correlation of the presence of flounce with meniscal location.For 8 months, 441 knee MR images were prospectively studied for meniscal flounce. Routine MRI was performed on a 10 degrees flexed knee, and flounce was seen in 22 medial menisci (5%). In all 22 of the patients with flounce, additional sagittal proton density-weighted MR images were obtained while the knees were both maximally flexed and maximally extended in a knee surface coil. We evaluated and compared the changes of degree of flounce and meniscal location on the tibial plateau among the three positions.With the maximally extended knee, the flounce disappeared in all cases but one. With the maximally flexed knee, the flounce disappeared in nine cases (9/22, 41%), was slightly released in 11 (11/22, 50%), and was accentuated in two (2/22, 9%). As the knees were more extended, the anterior horns of the menisci migrated more anteriorly, the posterior horns revealed subtle movement without a regular pattern, and the flounce was slightly released or disappeared.Active knee positioning in the knee surface coil changed the degree of meniscal flounce and the meniscal location on the tibial plateau. The meniscal flounce is thought to be a transient physiologic distortion and may be related to meniscal locations on the tibial plateau. It may be changed by varying the knee position.

OBJECTIVE. The aim of this work was to show the potential utility of a novel rapid 3D fat-suppressed MRI method for joint imaging.CONCLUSION. Phase-sensitive steady-state free precession provides rapid 3D joint imaging with robust fat suppression and excellent cartilage delineation.

The meniscus is considered "extruded" when it extends beyond the tibial margin. We hypothesize that severe degeneration, large radial tears, complex tears, and tears involving the meniscal root would alter meniscal stability and cause more substantial extrusion.The knee MRI database at Thomas Jefferson University Hospital was searched for reports describing meniscal extrusion; MR images were reviewed retrospectively. On mid coronal images, extrusion of the medial meniscus was quantified in millimeters. A separate, independent review of the meniscus evaluated degeneration severity and tear (type and extent). Radial tears were divided into those involving more (large) or less (small) than 50% of the meniscal width. Tears that involved the "root" at the tibial spine were recorded. Chi-square analysis compared these findings with extrusion extent, divided into minor (/= 3 mm) and major (3 mm) extrusion.One hundred five knees were reviewed (12 men and 93 women; age range, 34-83 years; mean age, 56 years). Distribution of medial meniscus extrusion was 2 mm (n = 17), 3 mm (n = 17), 4 mm (n = 27), 5 mm (n = 14), 6 mm (n = 16), and 7-10 mm (n = 14). Mild, moderate, or marked degeneration was seen in 47%, 26%, and 27% with minor extrusion, respectively, and in 17%, 41%, and 42% with major extrusion, respectively (p = 0.003). Tears were seen in 59% (20/34) with minor extrusion versus 89% (63/71) with major extrusion (p = 0.001). Tears involved one third, two thirds, or all of the meniscus in 75%, 25%, or 0%, respectively, with minor extrusion and 46%, 40%, or 14% with major extrusion, respectively (p = 0.014). Longitudinal (nonradial) and horizontal tears were not associated with extent of extrusion (p = 1.0). Oblique tears were significantly associated with minor extrusion (minor, 26% [9/34]; major, 4% [3/71]; p = 0.003). Radial tears were seen in 9% (3/34) with minor extrusion versus 21% (15/71) with major extrusion (p = 0.20). All three radial tears with minor extrusion were small; conversely, 87% (13/15) of radial tears with major extrusion were large (p = 0.019). Complex tears were seen in 18% (6/34) with minor extrusion versus 59% (42/71) with major extrusion (p0.001). Tears involving the meniscal root were seen in 3% (1/34) with minor extrusion and 42% (30/71) with major extrusion (p0.001).Substantial medial meniscus extrusion (3 mm) is associated with severe meniscal degeneration, extensive tear, complex tear, large radial tear, and tear involving the meniscal root.