Knee MRI: Meniscus Roots, Ramps, Repairs, and Repercussions.

Menisci play an essential role in maintaining normal pain-free function of the knee. While there are decades of MRI literature on the tears involving the meniscus body and horns, there is now a surge in knowledge regarding injuries at the meniscus roots and periphery. The authors briefly highlight new insights into meniscus anatomy and then summarize recent developments in the understanding of meniscus injuries that matter, emphasizing meniscus injuries at the root and peripheral (eg, ramp) regions that may be missed easily at MRI and arthroscopy. Root and ramp tears are important to diagnose because they may be amenable to repair. However, if these tears are left untreated, ongoing pain and accelerated cartilage degeneration may ensue. The posterior roots of the medial and lateral menisci are most commonly affected by injury, and each of these injuries is associated with distinctive clinical profiles, MRI findings, and tear patterns. Specific diagnostic pitfalls can make the roots challenging to evaluate, including MRI artifacts and anatomic variations. As with root tears, MRI interpretation and orthopedic treatment have important differences for injuries at the medial versus lateral meniscus (LM) periphery (located at or near the meniscocapsular junction). Medially, ramp lesions typically occur in the setting of an anterior cruciate ligament rupture and are generally classified into five patterns. Laterally, the meniscocapsular junction may be injured in association with tibial plateau fractures, but disruption of the popliteomeniscal fascicles may also result in a hypermobile LM. Updated knowledge of the meniscus root and ramp tears is crucial in optimizing diagnostic imaging before repair and understanding the clinical repercussions. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available in the Online Learning Center.

Patellar Tracking: An Old Problem with New Insights.

Patellofemoral pain and instability are common indications for imaging that are encountered in everyday practice. The authors comprehensively review key aspects of patellofemoral instability pertinent to radiologists that can be seen before the onset of osteoarthritis, highlighting the anatomy, clinical evaluation, diagnostic imaging, and treatment. Regarding the anatomy, the medial patellofemoral ligament (MPFL) is the primary static soft-tissue restraint to lateral patellar displacement and is commonly reconstructed surgically in patients with MPFL dysfunction and patellar instability. Osteoarticular abnormalities that predispose individuals to patellar instability include patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Clinically, patients with patellar instability may be divided into two broad groups with imaging findings that sometimes overlap: patients with a history of overt patellar instability after a traumatic event (eg, dislocation, subluxation) and patients without such a history. In terms of imaging, radiography is generally the initial examination of choice, and MRI is the most common cross-sectional examination performed preoperatively. For all imaging techniques, there has been a proliferation of published radiologic measurement methods. The authors summarize the most common validated measurements for patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Given that static imaging is inherently limited in the evaluation of patellar motion, dynamic imaging with US, CT, or MRI may be requested by some surgeons. The primary treatment strategy for patellofemoral pain is conservative. Surgical treatment options include MPFL reconstruction with or without osseous corrections such as trochleoplasty and tibial tubercle osteotomy. Postoperative complications evaluated at imaging include patellar fracture, graft failure, graft malposition, and medial patellar subluxation. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Description and Validation of the Anterior Glenoid Angle: A Novel MRI-Based Measure of Glenoid Morphologic Features and Version.

The goal of this study was to establish a normal value for, and evaluate the reliability of, a new measurement of glenoid morphologic features using magnetic resonance imaging: the anterior glenoid angle. A total of 90 magnetic resonance imaging scans of patients without shoulder arthritis were reviewed. The anterior glenoid angle of each glenoid was measured by 4 blinded physicians. The images were randomized and measured again. Finally, the Friedman angle was measured on the same images for reference. Descriptive statistics and inter- and intraclass correlation coefficients were calculated. The mean anterior glenoid angle was 60.4°±3.6°. Of the measured values, 77% were between 56° and 64°. Intraobserver reliability was very good to excellent in single measure (range, 0.763-0.901) and mean measure (range, 0.865-0.948) comparisons. Interobserver reliability was very good to excellent in both single measure (0.769) and mean measure (0.964) comparisons. The mean Friedman angle was 10.2°. Correlation between the anterior glenoid angle and Friedman angle ranged from a moderate negative (-0.496) to a strong negative correlation (-0.711) among the observers. The mean anterior glenoid angle measured via magnetic resonance imaging scan was 60.4° in normal shoulders, and more than 75% of the values were within 4° of the mean. The anterior glenoid angle has excellent inter- and intrarater reliability without using computed tomography scan or including the entire scapula in the field of view. The anterior glenoid angle has a good to very good negative correlation with the Friedman angle because decreasing anterior glenoid angles indicate increasing retroversion. [Orthopedics. 2022;45(6):361-366.].

Displaced Flap Tears of the Triangular Fibrocartilage Complex: Frequency, Flap Location, and the "Comma" Sign on Wrist MRI.

The purposes of this study were to estimate the frequency of displaced triangular fibrocartilage complex (TFCC) tears and to describe their MRI characteristics. The total of 3411 wrist MRI examinations assessed showed 20 displaced TFCC tears in 17 patients (frequency, 0.5%). These flaps were characteristically connected to the TFCC via a pedicle ("comma" sign) in 19 of 20 cases and displaced into the distal radioulnar joint also in 19 of 20 cases. Management implications were considered.

Preoperative MRI of Articular Cartilage in the Knee: A Practical Approach.

Articular cartilage of the knee can be evaluated with high accuracy by magnetic resonance imaging (MRI) in preoperative patients with knee pain, but image quality and reporting are variable. This article discusses the normal MRI appearance of articular cartilage as well as the common MRI abnormalities of knee cartilage that may be considered for operative treatment. This article focuses on a practical approach to preoperative MRI of knee articular cartilage using routine MRI techniques. Current and future directions of knee MRI related to articular cartilage are also discussed.

Tears in the distal superficial medial collateral ligament: the wave sign and other associated MRI findings.

OBJECTIVE: To analyze the MRI characteristics of distal superficial medial collateral ligament (sMCL) tears and to identify features of tears displaced superficial to the pes anserinus (Stener-like lesion (SLL)). MATERIALS AND METHODS: Knee MRI examinations at four institutions were selected which showed tears of the sMCL located distal to the joint line. MRIs were evaluated for a SLL, a wavy contour to the sMCL, and the location of the proximal sMCL stump. Additional coexistent knee injuries were recorded. RESULTS: The study included 51 patients (mean age, 28 years [sd, 12]). A SLL was identified in 20 of 51 cases. The proximal stump margin was located significantly (p < 0.01) more distal and more medial with a SLL (mean = 33 mm [sd = 11 mm] and mean = 6.5 mm [sd = 2.5 mm], respectively), than without a SLL (mean = 19 mm [sd = 16 mm] and mean = 4.8 mm [sd = 2.4 mm], respectively). Medial compartment osseous injury was significantly (p < 0.05) more common with a SLL (75%) than without a SLL (42%). The frequency of concomitant injuries in the group (ACL tear, 82%; PCL tear, 22%; deep MCL tear, 61%; lateral compartment osseous injury, 94%) did not differ significantly between patients with and without a SLL. CONCLUSION: A distal sMCL tear should be considered when MRI depicts a wavy appearance of the sMCL. Distal sMCL tears have a frequent association with concomitant knee injuries, especially ACL tears and lateral femorotibial osseous injuries. A SLL is particularly important to recognize because of implications for treatment.

Magnetic resonance imaging of the postoperative meniscus: resection, repair, and replacement.

Meniscus surgery is common, and surgical indications and techniques continue to evolve. After highlighting relevant anatomy and emerging magnetic resonance (MR) imaging techniques, this article reviews the current indications and techniques used for meniscus surgery, evaluates the use of MR imaging protocols with and without arthrography, and focuses on MR imaging interpretation of the postoperative meniscus, with particular attention to clinical outcomes and diagnostic criteria.

MRI of snow skiing and snowboarding injuries.

Snow skiing has been called "the world's oldest sport," "the fastest non-motorized sport on Earth," and "the riskiest sport undertaken by adults on a routine basis." This article discusses the common mechanisms for orthopedic injuries occurring in two of the most popular winter sports in the world that have a reputation for an inherently high risk of injury: alpine skiing and snowboarding. The emphasis herein is on magnetic resonance imaging of characteristic injuries in skiers (knee, thumb, shoulder) and in snowboarders (wrist, forearm, ankle). Spine injuries in snowboarders and skiers are also discussed.

Radiographic and special studies: recent advances in imaging of the elbow.

Advanced imaging techniques such as computed tomography, ultrasound, and magnetic resonance imaging provide clinically useful information by detecting and characterizing pathologic conditions of the elbow. The information provided by these techniques can help establish an anatomic diagnosis in a noninvasive fashion. A timely and accurate imaging diagnosis may be an important piece of the puzzle in a diagnostic workup that allows implementation of proper treatment and improved outcome. In this article, the authors focus on recent advances in diagnostic imaging of the elbow joint.

Shoulder imaging in athletes.

Shoulder pain and injuries are common in athletes. Overhead athletes, in particular, place great demands on the shoulder and supporting structures. Magnetic resonance (MR) imaging is well suited to evaluation of the osseous structures and soft tissues of the shoulder and plays an important role in evaluation of shoulder pain in athletes. Primary extrinsic impingement is well evaluated on MR imaging as are the less common posterior superior glenoid impingement and subcoracoid impingement. Rotator cuff tendinosis as well as partial- and full-thickness tears are frequently encountered in the athletic shoulder. The biceps tendon and rotator interval capsular structures are important sources of shoulder pain. Glenohumeral instability that results from a traumatic event or atraumatic multidirectional recurrent instability is assessed. The biceps labral complex is a source of considerable anatomic variability and pathology.

MR imaging of meniscal and cruciate ligament injuries.

MR imaging provides clinically useful information in detecting and characterizing sports-related pathology of the menisci and cruciate ligaments in a noninvasive fashion. Meniscal tears can also be detected and characterized with regard to extent and tear stability with MR imaging. Acute and chronic tears of the anterior and posterior cruciate ligaments can be accurately identified and evaluated with MR imaging.

Clinical evaluation and treatment of spinoglenoid notch ganglion cysts.

Spinoglenoid notch cysts were identified by magnetic resonance imaging in 73 patients. Posterosuperior labral tears were identified in 65 patients who had spinoglenoid notch cysts. Patient follow-up was available on 88% of patients at a mean of 20.5 months after treatment. There were 52 men and 11 women, with a mean age of 39 years (range, 19-76 years). All patients reported shoulder pain. Infraspinatus atrophy occurred in 25 patients, weakness with external rotation in 43, and posterior shoulder tenderness in 30. Nineteen patients underwent nonoperative management of the cyst (group I). Eleven underwent attempted needle aspiration of the cyst (group II). Six had isolated arthroscopic treatment of a labral defect with no cyst excision (group III). Twenty-seven were treated with surgical cyst excision with the cyst and superior labral tear fixed arthroscopically or with an open approach in various combinations (group IV). Of the patients, 53% were satisfied in group I, 64% in group II, 67% in group III, and 97% in group IV.

Magnetic resonance imaging of sports-related injuries to the shoulder: impingement and rotator cuff.

MR imaging provides clinically useful information in detecting and characterizing sports-related pathology of the rotator cuff and other shoulder disorders in a non-invasive fashion. Complete and partial tears of the rotator cuff, as well as factors contributing to impingement, can be detected and characterized with MR imaging. The size and location of complete tears of the rotator cuff can be accurately determined with MR imaging.

Imaging of sports-related muscle injuries.

Muscle derangements in athletes have a wide variety of causes, treatments, and prognoses. Given that the cause and severity of sports-related injuries may be difficult to determine clinically in some cases, MR imaging is utilized increasingly to evaluate muscle injuries in athletes. After reviewing useful MR imaging techniques, this article focuses on MR imaging of the most common causes of muscle pain and disability in athletes, including myotendinous strain, delayed onset muscle soreness, muscle contusion, myositis ossificans, muscle laceration, muscle herniation, and compartment syndrome. The differential diagnosis of various signal intensity abnormalities in muscle also is reviewed.