The flipped meniscus sign

MRI in the Diagnosis of Bucket Handle Tears: What Is the Current Situation?

Introduction The purpose of this study was to determine the utility of current magnetic resonance imaging (MRI) in the diagnosis of bucket-handle meniscal tears. Materials and methods Patients treated for arthroscopic meniscal tears between March 2019 and March 2022 were reviewed. The current study included all patients with bucket handle tears diagnosed arthroscopically and having MRI scans (n=51). A control group of 58 individuals with similar demographic characteristics and meniscal tears apart from bucket handle tears was also formed. The assessment of bucket handle and non-bucket handle tears was performed blindly by a musculoskeletal (MSK) radiologist with 20 years of experience and a trainee radiologist, achieving consensus on group allocation. The MRIs were examined for various findings, including the presence of a bucket handle tear, tear location, presence of anterior cruciate ligament (ACL) rupture, intercondyler notch sign, double anterior horn sign, flipped meniscus sign, double posterior cruciate ligament (PCL) sign, absent bow sign, and the disproportionate posterior horn sign. These well-known signs, detailed in the literature, were evaluated. Additionally, less studied and less commonly known signs such as the V sign and double anterior cruciate ligament sign were assessed. The V sign appears similarly to the letter V, resulting from the displacement of the bucket handle tear and the angle of the intact meniscus on axial images. The double anterior cruciate ligament sign is the appearance formed by the compression of the displaced meniscal part behind the anterior cruciate ligament in bucket handle tears. Results Following the retrospective evaluation of MRI scans, 44 out of 51 tears diagnosed as bucket handle tears by arthroscopy were accurately identified (sensitivity: 86.27%). The same conclusion was reached for MRI scans in 52 out of 58 tears where arthroscopy did not detect a bucket handle tear (specificity: 89.66%). The most prevalent MRI signs in patients with bucket handle tears identified by arthroscopy in the study were the intercondylar notch sign (84.31%), V sign (72.55%), double PCL sign (56.86%), double anterior horn sign (49.02%), absent bow sign (43.14%), flipped meniscus sign (19.61%), disproportionate posterior horn sign (9.80%), and double ACL sign (5.88%). The intercondylar notch sign, V sign, and double PCL sign exhibited the highest sensitivity, while flipped meniscus, disproportionate posterior horn, and double ACL sign demonstrated the highest specificity. Conclusion MRI demonstrates a high level of sensitivity and specificity in identifying meniscal bucket handle tears, particularly when considering the eight MRI signs investigated in this study.

The Pelican Sign: Case Series Demonstrating A Unique Description of an Anteriorly Flipped Bucket-Handle Meniscal Tear of the Knee

Introduction Bucket-handle tears (BHTs) of the menisci are not uncommon and can occur in isolation or in conjunction with other injuries. The torn fragment can be displaced within the intercondylar notch or flipped anteriorly. In case of anterior flipped fragment, appearances of such tears on magnetic resonance imaging (MRI) scan have been described as various signs in literature (for example double posterior cruciate ligament sign, double delta sign) but mostly in the sagittal or coronal planes.

Purpose The aim of this study was to describe a unique ancillary sign that helps to identify this injury on the axial MRI plane where the anterior flipped BHT figuratively resembles a “pelican bird.”

Materials and Methods A retrospective review of MRI sequences of 10 consecutive patients over a 3-month period referred following a traumatic knee injury with anterior flipped meniscal tears was performed. Demographic details, clinical indication, and other associated features on the MRI were correlated following the observation of characteristic MRI appearance of a BHT.

Results All 10 patients (M:F = 7:3) with a mean age of 24.7 (17–38 years) presented following a twisting injury. 6 out of 10 patients had associated soft-tissue injuries in the knee visualized on the MRI. All patients demonstrated the distinctive “pelican bird” sign on the axial sequences of anterior flipped BHT of either menisci. This was not present with BHTs with displaced fragment within the intercondylar notch.

Conclusion We conclude that the “pelican sign” on an axial sequence when present correlates well with a BHT and its anterior displaced/flipped meniscal fragment. This ancillary sign can complement other previously described signs on different MRI sequences used to confirm a displaced BHT.

Selective Unique Signs of Meniscus Tears as Visualized by Magnetic Resonance Imaging

The meniscus is an organized collection of fibrocartilaginous tissue that is located between the femoral condyles and the tibial plateau of the knee which primarily assists with load transmission. The complex composition of articulating soft-tissue structures in the knee causes the menisci to become a common source of injury, especially in the realm of athletic trauma. Magnetic resonance imaging (MRI) has become the imaging modality of choice for evaluating patients with suspected meniscal pathology because of its numerous advantages over plain radiographs. Most forms of meniscal tears have classic MRI findings and are used in correlation with physical examination findings to confirm or rule out a diagnosis. These imaging findings are referred to as signs and have been well studied, and the associated eponyms for each sign are well published throughout the literature. This article will review and describe a unique selection of meniscal pathology as visualized by MRI that is more commonly published in musculoskeletal radiology literature when compared with orthopedics and sports medicine literature.

Spontaneous Healing of a Posteriorly Displaced Lateral Meniscus Bucket-Handle Tear in a Multiligament Knee Injury: A Case Report

CASE

Bucket-handle meniscus tears (BHMTs) typically involve the medial meniscus and often occur with concomitant rupture of the anterior cruciate ligament. We report an unusual case of a polytrauma patient who sustained a bicruciate multiligament knee injury (MLKI) with a posteriorly displaced lateral BHMT that spontaneously healed after reduction of the fragment. At the 2-year follow-up, the lateral meniscus was clinically stable without pain.

CONCLUSION

A lateral BHMT with a posteriorly displaced fragment produced an atypical magnetic resonance imaging presentation in a bicruciate MLKI. Meniscal repair was aborted because of extravasation and concerns of compartment syndrome, but spontaneous healing occurred after fragment reduction.

The "sleeper's sign" is valid and suggestive of a medial sub-meniscal flap tear

PURPOSE

To describe, evaluate and validate the diagnostic performance of a new clinical sign, the sleeper's sign, for the diagnosis of a medial submeniscal flap tear (MSMFT).

METHODS

This retrospective single-center series included patients aged 18-55 years old who underwent arthroscopic treatment in 2013-2015 for a medial meniscal tear. This study was performed according to STARD (standards for reporting of diagnostic accuracy) guidelines, and the reference test was a peroperative diagnosis of a MSMFT. The preoperative consultation reports were all analyzed to search for the sleeper's sign, defined as night time medial tibiofemoral pain when the patient is in the fetal position with both knees in contact and no pain during daytime activities.

RESULTS

Three-hundred and ten patients responded to the study criteria, mean age 41.7 ± 9.7 years old. The sleeper's sign was identified in 39 (12.6%) patients and a MSMFT was confirmed during arthroscopy in 47 (15.2%) cases, with significant agreement between this sign, arthroscopy (kappa = 0.78, p = 10^-4) and MR-imaging (kappa = 0.72, p < 0.0001). The performance parameters of the sleeper's sign were: sensitivity 74.5 ± 12.5%, specificity 98.5 ± 1.6%, Youden index 0.73 and accuracy 96.9%. MR imaging was found to be more sensitive (91.5 ± 8%). Multivariate analysis identified the sleeper's sign as a risk factor of MSMFT during arthroscopy: OR 131.9 CI 95% [26.9-646.2], p < 0.0001 and a bone edema next to the flap tear on MR-imaging: OR 13, CI 95% [1.9-7.1], p = 0.008.

CONCLUSION

The "sleeper's sign" is a new, valid, highly specific clinical sign for the diagnosis of a medial submeniscal flap tear. MRI was found to be more sensitive than the sleeper's sign.

LEVEL OF EVIDENCE

II.

Illustrative review of knee meniscal tear patterns, repair and replacement options, and imaging evaluation

This review article aims to reinforce anatomical concepts about meniscal tears while linking associated treatment options. The main teaching points start with the basic meniscal anatomy and key differences between the medial and lateral menisci. Subsequently, various meniscal tear patterns along with their associated history and physical exam findings will be discussed with corresponding illustrations and MR images. Additional discussion will involve the different surgical repair techniques (with arthroscopic correlates), their indications with pertinent imaging findings, imaging related to previous meniscal tear repairs, and novel surgical techniques. Lastly, keys to evaluating for retear with an emphasis on MRI arthrogram findings will be reviewed. While each of these topics is not discussed in totality, the key points of the review article will enforce key concepts and help radiologists evaluate the menisci on imaging.

The double ACL sign: An aberrant bucket-handle tear of lateral meniscus

Introduction

Meniscal injuries are one of the most common musculoskeletal injuries around the knee affecting patients of different genders, ages and activity levels. These injuries could be acute or chronic tears that cause pain and mechanical symptoms based on the injury severity and whether it is displaced and entrapped in an abnormal location within the knee or not. Advances in magnetic resonance imaging (MRI) allowed us to have a better understanding of multiple bucket handle meniscal tear patterns with its specific MRI signs which have been reported in the literature.

Case presentation

This report presents a rare case of a 16-year-old boy with atypical bucket-handle tear of lateral meniscus and MRI showed a bucket-handle tear of lateral meniscus with a fragment entrapped behind and parallel to the anterior cruciate ligament (ACL) appearing as another ACL in sagittal views. Meniscus was repaired arthroscopically.

Conclusion

In our case, the unique and infrequent mechanism led to a bucket-handle tear involving lateral meniscus with a meniscal fragment entrapped in an unusual place intra-articularly behind ACL giving the appearance of a rare MRI sign “double ACL sign”. However, double ACL sign secondary to lateral meniscal tear has been reported only once previously up to the authors’ knowledge.

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Radiologically, meniscal tears have multiple pathognomatic signs.

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Double acl sign was reported twice only, one from medial meniscus and the other from lateral meniscus.

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Double acl sign indicates huge bucket handle tear which displaced into the intercondylar notch.

A Case of Bilateral Permanent Subluxation of the Lateral Meniscus

We report a case of bilateral, permanent subluxation of the lateral meniscus. To our knowledge, the present case is the first reported description of bilateral irreducible anterior dislocation of the posterior segment of the lateral meniscus. This disorder is characterized by a flipped meniscus sign of the lateral meniscus on sagittal magnetic resonance images of the knee joint, with no history of trauma or locking symptoms. A detailed examination of serial magnetic resonance images of the lateral meniscus can help differentiate this condition from malformation of the lateral meniscus, that is, a double-layered meniscus. We recommend two-stage treatment for this disorder. First, the knee joint is kept in straight position for 3 weeks after the lateral meniscus is reduced to the normal position. Second, if subluxation of the lateral meniscus recurs, meniscocapsular suture is then performed. Although subluxation of the lateral meniscus without locking symptoms is rare, it is important to be familiar with this condition to diagnose and treat it correctly.

Self-Reduction of Displaced Bucket-Handle Medial Meniscal Tear in a 71-Year-Old Patient: A Case Report

Background:

Bucket-handle meniscal tears are rare in geriatric patients. Displaced bucket-handle meniscal tears are usually treated operatively. Due to the rarity of these tears in elderly patients and conflicting evidence regarding the use of arthroscopy versus conservative treatment, it is valuable to report the clinical presentation, treatment, and outcome of these injuries in elderly patients.

Case Description:

We describe a 71-year-old man who presented with an acute, displaced, magnetic resonance imaging (MRI)-confirmed right medial meniscal bucket-handle tear with mild effusion and no signs of degenerative joint disease. On physical examination, the patient was unable to fully extend the right leg due to locking of the knee. At 2-month follow-up, MRI showed mild degenerative changes and an anatomically reduced tear. At 6-month follow-up, the patient reported normal, pain-free knee function, and MRI showed the tear healing in anatomic position with minimal inferior surface changes and no effusion. He returned to his pain-free baseline level of physical activity.

Literature Review:

Upon review of the English literature, this 71-year-old patient is an exceptional case and one of the oldest patients reported to have sustained a displaced medial meniscal bucket-handle tear treated successfully with nonoperative means. Two reported cases of spontaneously reduced meniscal bucket-handle tears were found in the English literature, although both cases were seen in much younger males and involved the lateral meniscus.

Clinical Relevance:

This case suggests that in elderly patients with displaced medial meniscus bucket-handle tears that reduce spontaneously, the physician can safely and efficaciously use conservative, nonoperative management to achieve restoration of baseline knee function and anatomic meniscal healing while avoiding the risks of arthroscopic surgery. Surgical intervention for reduction without repair may be an available option, but no literature is present to direct care; however, complete documentation as in the current case would be instructive. Katz et al have reported that physical therapy was as efficacious as surgical intervention, although the specific displaced bucket-handle tear was not reported.

MR imaging-based diagnosis and classification of meniscal tears

Magnetic resonance (MR) imaging is currently the modality of choice for detecting meniscal injuries and planning subsequent treatment. A thorough understanding of the imaging protocols, normal meniscal anatomy, surrounding anatomic structures, and anatomic variants and pitfalls is critical to ensure diagnostic accuracy and prevent unnecessary surgery. High-spatial-resolution imaging of the meniscus can be performed using fast spin-echo and three-dimensional MR imaging sequences. Normal anatomic structures that can mimic a tear include the meniscal ligament, meniscofemoral ligaments, popliteomeniscal fascicles, and meniscomeniscal ligament. Anatomic variants and pitfalls that can mimic a tear include discoid meniscus, meniscal flounce, a meniscal ossicle, and chondrocalcinosis. When a meniscal tear is identified, accurate description and classification of the tear pattern can guide the referring clinician in patient education and surgical planning. For example, longitudinal tears are often amenable to repair, whereas horizontal and radial tears may require partial meniscectomy. Tear patterns include horizontal, longitudinal, radial, root, complex, displaced, and bucket-handle tears. Occasionally, meniscal tears can be difficult to detect at imaging; however, secondary indirect signs, such as a parameniscal cyst, meniscal extrusion, or linear subchondral bone marrow edema, should increase the radiologist's suspicion for an underlying tear. Awareness of common diagnostic errors can ensure accurate diagnosis of meniscal tears. Online supplemental material is available for this article.

The Trapped Medial Meniscus Tear: An Examination Maneuver Helps Predict Arthroscopic Findings

Background:

Numerous clinical examination maneuvers have been developed to identify meniscus tears of the knee. While meniscus injuries vary significantly in type and severity, no maneuvers have been developed that help to distinguish particular tear characteristics.

Purpose:

This nonconsecutive case series highlights a distinctive clinical finding that correlates with inferiorly displaced flap tears of the medial meniscus that become trapped in the medial gutter of the knee, as identified through magnetic resonance imaging (MRI) and arthroscopy.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

Eight patients with trapped medial meniscus tears were identified from a single surgeon’s academic orthopaedic sports medicine practice between January 2009 and January 2012. Each patient underwent clinical evaluation, MRI, and arthroscopic treatment for meniscus injury. Clinical notes, MRI images, radiology reports, and operative findings were reviewed and compared in a descriptive fashion.

Results:

Each patient displayed a positive clinical examination finding of medial knee pain inferior to the joint line with flexion and the application of valgus stress in the setting of a torn medial meniscus and intact medial collateral ligament (MCL). Preoperative MRI revealed a distinctive flap tear of the medial meniscus flipped inferiorly to lay trapped between the tibia and deep fibers of the MCL. On arthroscopy, flap tears were found displaced inferiorly and trapped in the medial gutter in 6 of the 8 patients. Displaced meniscal fragments in the remaining 2 patients were found within the medial compartment.

Conclusion:

Inferiorly displaced flap tears of the meniscus that have been displaced to the medial gutter can be localized through a careful examination technique.

Clinical Relevance:

Early identification of this injury pattern may help reduce the likelihood that the trapped fragment will be missed during arthroscopy.

MRI imaging of displaced meniscal tears: Report of a case highlighting new potential pitfalls of the MRI signs

Magnetic resonance imaging (MRI) has been found to be an excellent imaging tool for meniscal injuries. Various MRI signs have been described to detect displaced meniscal injuries, specifically the bucket-handle tears. Although these signs are quite helpful in diagnosing meniscal tears, various pitfalls have also been reported for these signs. Double anterior cruciate ligament (ACL) sign refers to presence of a linear hypointense soft tissue anterior to the ACL, which represented the flipped bucket-handle tear of the meniscus. Disproportional posterior horn and flipped meniscus signs represent asymmetrically thickened horns of the menisci due to overlying displaced meniscal fragments. We report a case wherein MRI of the knee showed tear and displacement of the medial patellofemoral ligament (MPFL) and vastus medialis complex, medial collateral ligament (MCL), and posterior cruciate ligament (PCL) mimicking these signs. To our knowledge, internally displaced MPFL and MCLs have not been described as mimics for displaced meniscal fragments.

The double flipped meniscus sign: unusual MRI findings in bucket-handle tear of the lateral meniscus

Bucket-handle meniscal tears are either longitudinal, vertical, or oblique in direction with an attached tear fragment displaced from the meniscus. Magnetic resonance imaging (MRI) signs are widely used in the diagnosis of these tears, including the 'fragment within the intercondylar notch sign', 'flipped meniscus sign', 'double anterior horn sign', 'absence of the bow tie sign', 'double posterior cruciate ligament (PCL) sign', 'posterior double PCL sign', and 'triple PCL sign'. We report an unusual case, not yet described in previous studies, of a bucket-handle tear presenting as a double longitudinal tear of the lateral meniscus (LM). Two longitudinal tears were observed in the white-white zone and the red-white zone of the LM, where both fragments were shown to be displaced and locked within the intercondylar notch. Partial menisectomy was performed for the central fragment and a repair with modified all-inside sutures was performed for the peripheral fragment.

How I diagnose meniscal tears on knee MRI

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.

Bucket-handle meniscal tear in a 5-year-old child

Bucket-handle meniscus tears are a common athletic injury that occur frequently in the adult population but are extremely rare in young children. A 5-year-old male patient presented with left knee pain after a minor fall to the ground. Complaints of pain with full weight-bearing, locking of the joint during walking, a significant limp, 45° flexion contracture of the knee, and an inability to bring the leg into full extension were noted during examination. MRI showed a large bucket-handle medial meniscal tear. The patient made a full recovery after undergoing arthroscopic repair surgery. Level of evidence Case report, Level IV.

Arthroscopic partial meniscectomy of a posteriorly flipped superior leaflet in a horizontal medial meniscus tear using a posterior transseptal portal

This article describes a case of an arthroscopic partial meniscectomy of a posteriorly flipped superior leaflet in a horizontal medial meniscus tear using the posterior transseptal portal. An arthroscopic partial meniscectomy for bucket handle or flap tears in medial or lateral compartments using ordinary portals is a relatively common procedure in irreparable cases. However, the posterior compartment of the knee is not readily accessible through ordinary arthroscopic portals. Therefore, it has been considered a blind spot. Through the posterior transseptal portal, surgeons can achieve excellent arthroscopic visualization of the posterior compartment and easily perform arthroscopic procedures of the posterior compartment of the knee. A 48-year-old woman presented with a 1-year history of pain in the medial aspect of the right knee joint. Preoperative magnetic resonance imaging revealed a thinning of the medial meniscus posterior horn in coronal images and a sharp-edged triangle arising from the medial meniscus posterior horn between the medial femoral condyle and medial meniscus posterior horn on sagittal images (flipped-over sign). During the arthroscopic procedure, we found that the flipped leaflet was displaced posteriorly and was not mobile between the medial femoral condyle and medial meniscus posterior horn. Partial meniscectomy for a posteriorly displaced fragment can be performed successfully using the posterior transseptal portal. The posterior transseptal portal is useful for an arthroscopic partial meniscectomy of a posteriorly flipped leaflet in the posterior compartment of the knee.

Vacuum phenomenon: prevalence and appearance in the knee with 3 T magnetic resonance imaging

OBJECTIVES

To determine the prevalence of vacuum phenomenon (VP) in the knee on magnetic resonance (MR) images, describe the imaging features that characterize VP, and assess how often VP mimics pathological knee lesions.

MATERIALS AND METHODS

Consecutive knee MR studies performed on a 3 T MR system over a 9-month period were retrospectively reviewed by one radiologist who then selected studies with findings potentially indicating VP. Three experienced musculoskeletal radiologists reviewed these cases in consensus to confirm the presence of VP and to assess the shape, size, and signal of VP; the presence of magnetic susceptibility artifacts; and the ability of MR sequences to show VP.

RESULTS

A total of 914 consecutive exams from 875 patients (524 men; mean age, 35 years) were reviewed. Vacuum phenomenon was found in 12 patients (prevalence 1.3%). In six (50%) patients, VP mimicked a meniscal tear, with four cases simulating a torn medial discoid meniscus. The VP signal was not easily differentiated from meniscal signal on most sequences in most cases (9/12). Gradient-recalled echo (GRE) localizer images proved most definitive, with 3D SPACE images the next most effective. Fast spin echo (FSE) images were only occasionally able to differentiate VP from meniscus.

CONCLUSION

Rarely recognized on MR, VP can mimic meniscal pathology, potentially leading to inappropriate surgery. Because differentiation of VP from the meniscus is challenging on FSE at 3 T, radiologists should become familiar with the appearance of VP and review GRE localizer or 3D images carefully to avoid misinterpretation.

The double ACL sign: an unusual bucket-handle tear of medial meniscus

Several characteristic magnetic resonance imaging (MRI) signs of meniscal bucket-handle tears are well known and widely used. This case report presents a new MRI sign of a meniscal bucket-handle tear. A 17-year-old boy visited our hospital because of the pain in his left knee. Preoperative MRI on sagittal view showed a tear in the anterior horn of the medial meniscus and a displaced fragment of the medial meniscus in front of the original anterior cruciate ligament (ACL), which looks like another ACL. Under arthroscopic examination, the bucket-handle medial meniscus displaced parallel to the ACL was observed. A longitudinal tear was extended from the anterior horn to the posterior horn of medial meniscus. To our knowledge, this new MRI sign of bucket-handle tear, "the double ACL sign", has not been previously reported. Level of evidence V.

Association of internal rotation of the knee joint with recurrent subluxation of the lateral meniscus

PURPOSE

To compare the arc of rotation of the knee joint at 90° of flexion in control knee joints and those affected by recurrent subluxation of the lateral meniscus (RSLM), in determining whether rotatory instability of the knee joint is a risk factor for RSLM.

METHODS

Knee joints were diagnosed with RSLM when there was a history of mechanical locking episodes and when subluxation of the lateral meniscus with the peripheral margin of the posterior segment moving anteriorly beyond the lateral femoral condyle was recognized on arthroscopy. In this study 288 knee joints in 270 subjects were evaluated. The joints were classified into a control group (252 joints), an RSLM group (24 joints), and a contralateral RSLM group (12 joints). The arcs of external and internal rotation at 90° of flexion of the knee joint induced by 7 Nm of torque under non-weight-bearing conditions were measured with a Biodex System 3 (Biodex Medical Systems, Shirley, NY).

RESULTS

There were no significant differences in mean values of external rotation among the 3 groups. The mean values of internal rotation of both the RSLM and contralateral RSLM groups were significantly larger than that of the control group, by about 15° (P < .0001). The mean value of internal rotation was slightly higher than that of external rotation in the RSLM and contralateral RSLM groups, although the mean value of internal rotation was smaller than that of external rotation by 10.1° in the control group.

CONCLUSIONS

RSLM was found to be strongly related to bilateral increase in the arc of internal rotation at 90° of flexion of the knee joint, suggesting that internal rotatory instability of the flexed knee joint can be considered one of the risk factors for and diagnostic parameters of RSLM.

LEVEL OF EVIDENCE

Level III, diagnostic study of nonconsecutive patients.

The triple PCL sign: bucket handle tears of both medial and lateral menisci in a chronically ACL-deficient knee

Bucket handle tears of both menisci in the setting of acute or chronic anterior cruciate ligament (ACL) tears of the same knee have rarely been reported in the literature. This article presents a case of a bucket handle tear affecting both the medial and lateral menisci in a patient with chronic ACL rupture. Both bucket handle tears were displaced and locked in the intercondylar notch. A new magnetic resonance image (MRI) sign suggested on sagittal view is called the triple PCL sign, comprising the intact posterior cruciate ligament (PCL) and the 2 displaced fragments in the intercondylar notch from the two bucket handle tears. The precise diagnosis of this condition is of obvious importance for optimal operative planning. While finding the displaced fragment from the medial meniscus is expected to cause the double PCL sign, the torn ACL may have made it easier to visualize the bucket handle tear of the lateral meniscus in the same sagittal plane as the PCL. Only 5 other reports mention bimeniscal bucket handle tears of both the medial and lateral menisci in association with an ACL tear. None have shown the suggested triple PCL sign because of lack of overlap between the 2 bucket handle tears in the coronal plane while lying in the intercondylar notch causing them not to fall in the same sagittal plane. Our patient showed some overlap between the 2 meniscal fragments while lying in the notch to create the triple PCL sign on sagittal MRI.

Magnetic resonance imaging of the meniscus

Magnetic resonance imaging has evolved into a highly accurate modality in detecting meniscal injuries and provides the essential anatomic detail to help guide treatment options in this age of meniscal preservation. Accurate interpretation requires a thorough understanding of meniscal anatomy and function, anatomic variants, technical factors, typical appearance of tear patterns on magnetic resonance imaging, associated ligamentous injuries, causes of misdiagnoses, and the importance of correlation with the clinical examination.

Meniscal tears with displaced fragments: common patterns on magnetic resonance imaging

OBJECTIVE

To identify the commonly occurring patterns of small displaced tears of the menisci of the knee on magnetic resonance imaging (MRI).

MATERIALS AND METHODS

A retrospective review of knee MRI scans over 16 months at two hospitals provided 70 studies with 73 displaced meniscal fragments for analysis. Fragment position was recorded.

RESULTS

Two common positions were identified for medial fragments. For the medial meniscus, 93% of fragments were positioned medially or posterolaterally. The medially displaced fragments were positioned in either the superior or inferior recesses. Lateral meniscal fragments were more evenly dispersed.

CONCLUSION

The pattern of small displaced tears of the medial meniscus is highly predictable. Awareness of the typical locations of these fragments should aid the reporter in identifying these lesions on MRI.

Central hole tear of the discoid meniscus of the knee in magnetic resonance imaging: mimicking the bucket-handle tear

OBJECTIVE

To analyze the prevalence and describe the magnetic resonance imaging (MRI) features of central hole tear (CHT) of the discoid meniscus.

METHODS

Thirty-six patients with arthroscopically proven CHT who underwent knee MRI were included. We retrospectively reviewed the clinical history and evaluated the MRI findings which have been known as the findings of bucket-handle tear (BHT) and osteoarthritis.

RESULTS

A CHT accounts for 15% of discoid meniscus tears. In all patients, CHT involved the lateral meniscus. Of 36 patients, 28 (78%) had not any history of trauma to the knee. Intercondylar notch sign, coronal truncation sign, absent bow tie sign, and flipped meniscus sign were seen in 36 (100%), 35 (97%), 34 (94%), and 10 patients (28%), respectively. In addition, 26 (72%), 21 (58%), and 17 (47%) of 36 patients showed osteophytes formation, chondral lesion, and subchondral bone change, respectively. Of these 36 patients, 23 (64%) and 22 (61%) demonstrated increased signal intensity in the meniscus on proton density-weighted image and irregularities of the margin of the residual menisci, respectively.

CONCLUSIONS

Although a CHT had many of the MRI features of BHT, it was usually accompanied by changes of osteoarthritis. Presence of degenerative change, absence of trauma, and presence in the lateral meniscus are features that favor a CHT over a BHT of the meniscus.

Meniscal gymnastics: common and uncommon locations of meniscal flip and flop

The majority of knee magnetic resonance imaging examinations are performed for meniscal evaluations. Displaced meniscal tears including free meniscal fragments are an important diagnosis as most of these tears are unstable and require surgical intervention. Magnetic resonance imaging can be an invaluable tool in the arthroscopic search for a free meniscal fragment. In addition to the commonly seen bucket-handle tears flipped into the intercondylar notch, it is important to be aware of less common locations where menisci may be displaced. First, we briefly summarize the basic meniscal anatomy and some of the more common tear patterns. We then investigate the broad range of meniscal migration.

Posterior double PCL sign: a case report of unusual MRI finding of bucket-handle tear of medial meniscus

Among the MRI signs of bucket-handle tears of medial meniscus, double posterior cruciate ligament (PCL) sign denotes a low signal band anterior and parallel to the PCL, which looks like another PCL in MR images. If the bucket-handle fragment subsequently tears at the anterior horn, the torn meniscal substance can be displaced to the posterosuperior region of the PCL, and looks like another PCL behind the original PCL. We propose the lesion be called the "posterior double PCL sign" in contrast to the ordinary double PCL sign. We present a case showing the posterior double PCL sign.

Anterior cruciate ligament injury with simultaneous locked bucket-handle tears of both medial and lateral meniscus in a 19-year-old female professional ski racer: a case report

Acute anterior cruciate ligament deficiency combined with simultaneous locked bucket-handle tears of both medial and lateral menisci have rarely been observed. This case report describes the first case of such a combined knee injury in an athlete including injury mechanism, clinical symptoms, specific signs on MRI, and treatment options.

Diagnostic IRM des lambeaux méniscaux médiaux déplacés le long du ligament tibial collatéral

PURPOSE OF THE STUDY

Displaced meniscus tears generally result from bucket handle tears with subsequent migration of the meniscal fragment into the intercondylar notch. More rarely, the fragment may move into the meniscal recesses. In this situation, the displaced fragment may be difficult to individualize arthroscopically, so preoperative imaging is crucial. Several studies have demonstrated the reliability of magnetic resonance imaging (MRI) for the diagnosis of meniscus injury with fragment displacement in the intercondylar notch. There have been few studies devoted to fragment displacement into the collateral capsuloligamentary structures. The purpose of this study was to describe MRI findings of medial meniscus tears with displaced fragment in the meniscal recesses.

MATERIAL AND METHODS

This prospective study was conducted over a 22-month period (May 2003 - February 2005). During this period, we selected 39 patients whose knee MRI displayed a meniscal fragment within the medial collateral recesses. These 39 patients accounted for 15% of knees with MRI-diagnosed meniscal tears (n=272) and 2% of the knee MRI examinations performed during the study period (n=2239). One the MRI series, we studied fragment migration and morphological anomalies of the injured meniscus. For 16 knees, MRI findings could be compared with arthroscopy findings.

RESULTS

For 25 knees (65%), the meniscal fragment had migrated downward along the medial tibial plateau and generally (64%) medially to the collateral tibial ligament. For 14 knees (35%) the meniscal fragment had migrated upward, along the medial femoral condyle in 93%, anteriorly to the medial collateral tibial ligament. For 95%, the MRI demonstrated rupture along the free border of the posterior segment and/or the mid segment of the medial meniscus or a decreased height of the posterior segment of the medial meniscus. For 14 of 16 cases, arthroscopy confirmed the meniscal tear and the localization of the displaced fragment. For two knees, arthroscopy confirmed the presence of the meniscal tear but could not identify the displaced meniscal fragment.

DISCUSSION

Meniscal tears with fragment displacement into the meniscal recesses has been associated with displacement of a horizontal fissuration which flap tears described arthroscopically by DJ Dandy. Other authors consider these tear flaps as oblique fissurations. In our study, it was sometimes difficult to determine the exact site and orientation of the initial meniscal tear so it is quite likely that meniscal tears with a displaced fragment in the meniscal recesses could correspond to complex predominantly horizontal or oblique meniscal fissurations. The common feature is the presence of an unstable meniscal flap susceptible to migrate. Our findings are in agreement with the literature. Regarding the two cases where the MRI findings could not be confirmed arthroscopically, the MRI visualized a characteristic image of a meniscal fragment displaced downwardly, lying between the medial tibial plateau and the collateral tibial ligament. Arthroscopy visualized the meniscal tear but failed to visualize the displaced fragment. This might be because mobile meniscal fragments return into the joint interspace when the meniscus is manipulated arthroscopically. Small meniscal fragments might also be inaccessible arthroscopically.

MRI for Traumatic Knee Injury: A Review

Magnetic resonance imaging (MRI) is a well-established technique for detecting internal derangements of the knee joint with high diagnostic accuracy. It is an effective tool to select patients for targeted therapeutic arthroscopy. In this article, indications for knee MRI and most commonly used MRI techniques are outlined, followed by an overview of the most frequently encountered traumatic knee derangements in daily practice and their appearance and grading system on MRI. Lesions discussed include fractures, osteochondral lesions, bone bruise, cruciate and collateral ligament lesions, and meniscal tears. Finally, common pitfalls and recent developments in knee MRI are addressed.

Bucket-handle meniscal lesions: magnetic resonance imaging criteria for reparability

PURPOSE

The purpose of this study was to determine the accuracy of magnetic resonance imaging (MRI) in predicting knee bucket-handle meniscal tear (BHMT) reparability.

METHODS

Twenty-eight patients who underwent knee arthroscopy by a single surgeon for BHMT with prior MRI examination were included. BHMTs were diagnosed by MRI based on the association of a displaced meniscal fragment on coronal images and one of the following three signs on sagittal slices: flipped meniscus sign, double posterior cruciate ligament, and meniscal fragment within the intercondylar notch. BHMT patients' MRIs were retrospectively reviewed independently to search for criteria of reparability by 2 observers with different degrees of experience in musculoskeletal radiology, and disagreements were arbitrated to consensus. The criteria for BHMT reparability were as follows: (1) rim width of less than 4 mm; (2) tear length of 1 cm or greater, regardless of total lesion length; and (3) generation of isosignals by the inner meniscal fragment and peripheral rim compared with the normal contralateral meniscus of the same knee. The first 2 criteria indicate an adequate meniscal lesion length in the vascularized zone (only the peripheral third), enabling meniscal healing after repair; the third criterion guarantees that the meniscus is nondegenerative.

RESULTS

Of the BHMTs, 5 (17.9%) were arthroscopically reparable and 23 (82.1%) were not. Interpretation of magnetic resonance images correctly predicted reparability in 4 of 5 reparable BHMTs and irreparability in 22 of 23 irreparable BHMTs (26/28 lesions). Interobserver agreement was good for the prediction of reparability (kappa = 0.7).

CONCLUSIONS

These results suggest that knee BHMTs that are predicted to be reparable by MRI would have a high likelihood of actually being reparable.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria on basis of consecutive patients and gold standard.

Magnetic Resonance Imaging Appearance of a Double Anterior Cruciate Ligament Associated With a Displaced Tear of the Lateral Meniscus

The aim of this study is to report a novel description of a displaced tear of the lateral meniscus as a curvilinear low signal intensity band parallel and posteroinferior to the anterior cruciate ligament (ACL) on midline oblique sagittal magnetic resonance (MR) images, resulting in the appearance of a "double ACL." The appearance of a double ACL may potentially be a specific indicator for a lateral meniscal displaced tear. Increased awareness of this characteristic MR finding may increase accuracy in the diagnosis of displaced tears of the lateral meniscus.

The quadruple cruciate sign of simultaneous bicompartmental medial and lateral bucket-handle meniscal tears

We report the second known case of bicompartmental bucket-handle tears of the medial and lateral menisci and the first documented case of the bucket-handle tears occurring simultaneously following trauma, which occurred after a motorcycle accident. Both bucket-handle fragments were displaced into the intercondylar notch. An anterior cruciate ligament tear was also present. Coronal images demonstrated four structures in the intercondylar notch: the anterior and posterior cruciate ligaments and the medial and lateral bucket-handle meniscal fragments.

Meniscal Tears with Fragments Displaced in Notch and Recesses of Knee: MR Imaging with Arthroscopic Comparison

PURPOSE

To retrospectively evaluate magnetic resonance (MR) imaging for the depiction of meniscal tears with partially detached meniscal fragments displaced in the intercondylar notch or in the meniscal recesses of the knee.

MATERIALS AND METHODS

The institutional review board required neither its approval nor informed patient consent for the retrospective review of patient data; however, informed patient consent had been obtained before the MR imaging examinations were performed. The presence of meniscal tears with notch and recess fragments was determined at MR imaging and at subsequent arthroscopy in 101 consecutive knees to determine the value of MR imaging for the depiction of these lesions. Initial reports were reviewed to evaluate results of initial interpretations. MR images were retrospectively analyzed to determine the value of several MR image signs for the detection of displaced tears with notch or recess fragments.

RESULTS

At arthroscopy, 37 (41%) of 91 torn menisci had partially detached fragments. Twenty-six torn menisci had notch fragments, and 14 had recess fragments; three torn menisci had one notch and one recess fragment each. At initial MR image analysis, 38 (36%) of 105 torn menisci had partially detached fragments. Twenty-eight torn menisci had notch fragments, and 13 had recess fragments; one torn meniscus had two recess fragments, and three torn menisci had one notch and one recess fragment each. At initial analysis, sensitivities and specificities were, respectively, 69% and 94% for detection of tears with notch fragments and 71% and 98% for detection of tears with recess fragments. At retrospective analysis of sagittal MR images, the presence of at least one sign indicative of meniscal tear with a notch fragment had sensitivities and specificities, respectively, of 65% and 78% for observer 1 and 77% and 73% for observer 2. The presence of at least one sign indicative of a meniscal tear with a recess fragment had sensitivities and specificities, respectively, of 64% and 77% for observer 1 and 64% and 76% for observer 2.

CONCLUSION

Meniscal tears with notch and recess fragments are frequently seen at arthroscopy and can be depicted at knee MR imaging with moderate sensitivity and high specificity.

Bucket-handle meniscal tears of the knee: sensitivity and specificity of MRI signs

OBJECTIVE

To determine the sensitivity and specificity of reported MRI signs in the evaluation of bucket-handle tears of the knee.

DESIGN AND PATIENTS

A retrospective analysis of 71 knee MR examinations that were read as displaying evidence of a bucket-handle or "bucket-handle type" tear was performed. We evaluated for the presence or absence of the absent bow tie sign, the coronal truncation sign, the double posterior cruciate ligament (PCL) sign, the anterior flipped fragment sign, and a fragment displaced into the intercondylar notch. Sensitivity and specificity were calculated relative to the gold standard of arthroscopy.

RESULTS

Forty-three of 71 cases were surgically proven as bucket-handle tears. The absent bow tie sign demonstrated a sensitivity of 88.4%. The presence of at least one of the displaced fragment signs had a sensitivity of 90.7%. A finding of both the absent bow tie sign and one of the displaced fragment signs demonstrated a specificity of 85.7%. The double PCL sign demonstrated a specificity of 100%. The anterior flipped meniscus sign had a specificity of 89.7%.

CONCLUSIONS

Bucket-handle tears of the menisci, reported in about 10% of most large series, have been described by several signs with MRI. This report gives the sensitivity and specificity of MRI for bucket-handle tears using each of these signs independently and in combination. MRI is shown to be very accurate for diagnosing bucket-handle tears when two or more of these signs coexist.

MR imaging of the meniscus

It should be the goal of any radiologist who interprets MRI examinations of the knee to be able not only to recognize normal meniscal anatomy and accurately diagnose meniscal pathology, but also to develop a better grasp of the surgical implications of the imaging findings. By thinking more like an arthroscopist, one can provide a more clinically relevant report, and by doing so, add value to the work-up of a patient who presents with a potential meniscal tear.

Imaging of sports-related knee injuries

This article reviewed the major sports medicine conditions affecting the knee and their MR imaging appearance. MR imaging of the knee is considered efficacious especially in the setting of indeterminate clinical findings and can stratify patients, guiding further surgical management. MR imaging affects the diagnosis and management of acute knee injury by improving clinician diagnostic certainty, assisting in management decisions, and decreasing the number of arthroscopic procedures. From a societal perspective, knee MR imaging can be considered a cost-effective modality when compared with diagnostic and borderline therapeutic arthroscopies (e.g., debridement alone). For these and other reasons, knee MR imaging has shown a substantially increased use for the evaluation of sports medicine conditions.

Oblique meniscomeniscal ligament: another potential pitfall for a meniscal tear--anatomic description and appearance at MR imaging in three cases

Three patients with an arthroscopically proved normal variant, the oblique meniscomeniscal ligament, underwent prospective magnetic resonance (MR) imaging of the knee. In the first case, the ligament was misinterpreted as a displaced flap tear of the posterior horn of the lateral meniscus. In the two subsequent cases, the ligament was identified correctly at MR imaging as the oblique meniscomeniscal ligament.

Imaging of the knee. Current status

This article reviews the variety of imaging modalities that are currently being used to evaluate the knee. Nuclear scintigraphy is discussed with emphasis on prosthesis abnormalities. Sonography is discussed with regard to the evaluation of popliteal masses. The uses of computed tomography, especially in the evaluation of the tibial plateau fracture, are discussed, and the role of fluoroscopy, computed tomography, and sonography in image-guided needle procedures are reviewed. Emphasis is placed on the role of MR imaging in knee imaging, with attention to internal derangements, bursal and capsular pathology, and other assorted intra- and extra-articular disorders. The focus of this article is to review the wealth of information that may be obtained by using these imaging modalities.