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The objective of this article is to review the normal anatomy and posttraumatic findings of the Chopart joint complex. Key imaging features of the normal ligaments and patterns of ligamentous and osseous injuries are discussed.Traumatic midtarsal injuries, particularly midtarsal sprain, are often overlooked clinically and on imaging but are relatively common and typically are associated with inversion ankle injuries. Radiologists should be familiar with Chopart joint anatomy and the imaging features of midtarsal injuries because early diagnosis may help optimize clinical management.

The shoulder joint is the most unstable articulation in the entire human body. While this certainly introduces vulnerability to injury, it also confers the advantage of broad range of motion. There are many elements that work in combination to offset the inherent instability of the glenohumeral joint, but the glenoid labrum is perhaps related most often. Broadly, clinical unidirectional instability can be subdivided into anterior and posterior instability, which usually raise concern for anteroinferior and posteroinferior labral lesions, respectively. In the special case of superior labral damage, potential dislocation is blocked by structures that include the acromion; hence, while damage elsewhere commonly manifests as clinical instability, damage to the superior labrum is often described by the term microinstability. In this particular case, one of the radiologist's main concerns should be classic superior labral anteroposterior lesions. The glenoid labrum is also subject to a wide range of normal variants that can mimic labral tears. Knowledge of these variants is central to interpreting an imaging study of the labrum because misdiagnosis of labral variants as tears can lead to superfluous surgical procedures and decreased shoulder mobility. This article reviews labral anatomy and normal labral variants, describes their imaging features, and discusses how to discriminate normal variants from labral tears. Specific labral pathologic lesions are described per labral quadrant (anteroinferior, posteroinferior, and superior), and imaging features are described in detail. Online supplemental material is available for this article. ©RSNA, 2016.

The ankle is one of the most common sites of musculoskeletal injury. In a series of 1176 athletic injuries, 14% were found to be injuries of the ankle, and 85% of those were specifically sprains of ankle ligaments [1]. Although many ankle ligaments can be well assessed by an operator trained in ultrasound techniques, evaluation by magnetic resonance imaging (MRI) offers the advantages of a comprehensive and operator-independent examination [2]. In this article, a practical review of MRI of ankle ligaments is presented. The discussion is limited primarily to the ligaments surrounding the tibiotalar joint, particularly the inferior tibiofibular syndesmotic ligaments and the medial and lateral collateral ligaments (Table 1). Because of its close association with the deltoid ligament, the spring ligament is also included. Ligament names are represented by unambiguous abbreviations similar to those appearing in the literature [3e5]. For each ligament, normal anatomy, MRI appearance, and function will be addressed. Next, with regards to the injured ligament, basic mechanisms of injury will be reviewed, taking into consideration differing opinions in the literature that, in some cases, diverge from the classic teachings of Lauge and Hansen [3]. Because ligament injury usually manifests itself in similar ways, such as abnormal signal intensity (intrasubstance or periligamentous) or abnormal morphology (thickening, thinning, discontinuity, absence, irregularity, indistinctness, or heterotopic ossification) [2,4,6], additional imaging clues to injury that are ligamentspecific will be emphasized. Finally, because chronic injury

Magnetic resonance imaging (MRI) represents the preferred noninvasive imaging technique to diagnose meniscal pathology in the pre- and postoperative setting. Furthermore, characterization of meniscal tissue MR properties has been possible by the development of advanced MRI techniques. Suspected meniscal tears are a frequent indication for MRI and the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) classification system has been developed to facilitate accurate and uniform reporting of such meniscal tears. Partial meniscectomy and meniscal suture repair are among the commonly performed procedures and several signs have been described to detect postoperative recurrent tears on MRI. Other techniques that have proven useful for meniscal assessment are ultrasound (US) and computed tomography (CT) arthrography. In recent years, US is being increasingly used in the selective assessment of some meniscal pathology such as tears, parameniscal cysts and meniscal extrusion as it is a relatively inexpensive, accessible, and safe technique. CT arthrography has been advocated as an acceptable alternative in patients with contraindications for MRI, with comparable diagnostic performance.

To determine the feasibility of using MR microscopy to characterize the root ligaments of the human knee at both ultra-high-field (11.7 T) and high-field (3 T) strengths. Seven fresh cadaveric knees were used for this study. Six specimens were imaged at 11.7 T and one specimen at 3 T using isotropic or near-isotropic voxels. Histologic correlation was performed on the posteromedial root ligament of one specimen. Meniscal root ligament shape, signal intensity, and ultrastructure were characterized. High-resolution, high-contrast volumetric images were generated from both MR systems. Meniscal root ligaments were predominantly oval in shape. Increased signal intensity was most evident at the posteromedial and posterolateral root ligaments. On the specimen that underwent histologic preparation, increased signal intensity corresponded to regions of enthesis fibrocartilage. Collagen fascicles were continuous between the menisci and root ligaments. Predominantly horizontal meniscal radial tie fibers continued into the root ligaments as vertical endoligaments. MR microscopy can be used to characterize and delineate the distinct ultrastructure of the root ligaments on both ultra-high-field- and high-field-strength MR systems.

The glenohumeral joint is a classic ball and socket type joint which allows a broad range of movement but whose shallow glenoid component compromises the inherent stability of the joint. Only 25–30% of the humeral head contacts the glenoid surface [1]. The joint is fortified by both intrinsic and extrinsic components. Compromise of any of the intrinsic or extrinsic stabilizers of the joint can lead to joint laxity and result in either unidirectional or multidirectional glenohumeral instability.Imaging, specifically MRI and MR arthrography, provides a reliable means of identifying structural features contributing-to or associated with glenohumeral instability, which may be critical factors in determining optimal management of patients with instability of the glenohumeral joint.

Following a brief description of the normal anatomy and biomechanics of the midfoot, this article focuses on MR imaging features of common osseous, tendon, and ligament abnormalities that affect the midfoot. Discussion of the anatomy and pathology affecting the Chopart and Lisfranc joint complexes, both of which play important roles in linking the midfoot to the hindfoot and the forefoot respectively, is also included.

Ankle impingement syndromes encompass a broad spectrum of post-traumatic and chronic degenerative changes that present with pain on specific movements about the ankle joint. Both amateur and professional athletes are disproportionately affected by these conditions, and while conservative measures can potentially treat an impingement syndrome, definitive therapy is often alleviated surgically. Imaging (including conventional radiography, ultrasound, CT and MRI) plays an invaluable role in the diagnosis and pre-surgical work-up. An anatomically based classification system is useful in these syndromes, as the aetiology, sites of pathology and preferred treatment methods are similarly based on anatomic locations about the ankle. This review focuses on the anatomic locations, pathophysiology, imaging considerations and brief discussion of therapies for each of the major anatomic ankle impingement syndromes.

Author(s): Iwasaki, Kenyu; Tafur, Monica; Chang, Eric Y; Statum, Sheronda; Biswas, Reni; Tran, Betty; Bae, Won C; Du, Jiang; Bydder, Graeme M; Chung, Christine B | Abstract: ObjectiveThis study aimed to implement qualitative and quantitative magnetic resonance sequences for the evaluation of labral pathology.MethodsSix glenoid labra were dissected, and the anterior and posterior portions were divided into normal, mildly degenerated, or severely degenerated groups using gross and magnetic resonance findings. Qualitative evaluation was performed using T1-weighted, proton density-weighted, spoiled gradient echo and ultrashort echo time (UTE) sequences. Quantitative evaluation included T2 and T1rho measurements as well as T1, T2*, and T1rho measurements acquired with UTE techniques.ResultsSpoiled gradient echo and UTE sequences best demonstrated labral fiber structure. Degenerated labra had a tendency toward decreased T1 values, increased T2/T2* values, and increased T1rho values. T2* values obtained with the UTE sequence allowed for delineation among normal, mildly degenerated, and severely degenerated groups (P l 0.001).ConclusionsQuantitative T2* measurements acquired with the UTE technique are useful for distinguishing among normal, mildly degenerated, and severely degenerated labra.

To implement high-resolution morphologic and quantitative magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) using ultrashort time-to-echo (UTE) techniques in cadavers and volunteers. This study was approved by the institutional review board. TMJs of cadavers and volunteers were imaged on a 3-T MR system. High-resolution morphologic and quantitative sequences using conventional and UTE techniques were performed in cadaveric TMJs. Morphologic and UTE quantitative sequences were performed in asymptomatic and symptomatic volunteers. Morphologic evaluation demonstrated the TMJ structures in open- and closed-mouth position. UTE techniques facilitated the visualization of the disc and fibrocartilage. Quantitative UTE MRI was successfully performed ex vivo and in vivo, reflecting the degree of degeneration. There was a difference in the mean UTE T2* values between asymptomatic and symptomatic volunteers. MRI evaluation of the TMJ using UTE techniques allows characterization of the internal structure and quantification of the MR properties of the disc. Quantitative UTE MRI can be performed in vivo with short scan times.

The purposes of this study were to determine the prevalence of altered MRI appearances of "posterior medial meniscus root ligament (PMMRL)" lesions, introduce a classification of lesion types, and report associated findings.We retrospectively reviewed 419 knee MRI studies to identify the presence of PMMRL lesions. Classification was established on the basis of lesions encountered. The medial compartment was assessed for medial meniscal tears in the meniscus proper, medial meniscal extrusion, insertional PMMRL osseous changes, regional synovitis, osteoarthritis, insufficiency fracture, and cruciate ligament abnormality.PMMRL abnormalities occurred in 28.6% (120/419) of the studies: degeneration, 14.3% (60/419) and tear, 14.3% (60/419). Our classification system included degeneration and tearing. Tearing was categorized as partial or complete with delineation of the point of failure as entheseal, midsubstance, or junction to meniscus. Of all tears, 93.3% (56/60) occurred at the meniscal junction. Univariate analysis revealed significant differences between the knees with and without PMMRL lesions in age, medial meniscal tear, medial meniscal extrusion, insertional PMMRL osseous change, regional synovitis, osteoarthritis, insufficiency fracture (p=0.017), and cruciate ligament degeneration (p0.001).PMMRL lesions are commonly detected in symptomatic patients. We have introduced an MRI classification system. PMMRL lesions are significantly associated with age, medial meniscal tears, medial meniscal extrusion, insertional PMMRL osseous change, regional synovitis, osteoarthritis, insufficiency fracture, and cruciate ligament degeneration.