MR imaging of the meniscus

Pediatric menisci: normal aspects, anatomical variants, lesions, tears, and postsurgical findings

The reported incidence of meniscal tears in the pediatric age group has increased because of increased sports participation and more widespread use of MRI. Meniscal injury is one of the most commonly reported internal derangements in skeletally immature knees and can be associated with early degenerative joint disease leading to disability. The pediatric meniscus has particularities, and knowledge of normal anatomy, anatomical variations, and the patterns of meniscal injury in the pediatric age group is essential to provide a correct diagnosis. CRITICAL RELEVANCE STATEMENT: Accurate MRI interpretation of pediatric meniscal injuries is crucial. Understanding age-specific anatomy, vascularity, and variations can improve diagnostic precision, guiding targeted treatments to prevent early joint degeneration and disability. KEY POINTS: Meniscal lesions are common injuries in skeletally immature knees. Awareness of anatomical meniscus variants, patterns of injury, and associated injuries is essential. Meniscal tears in pediatric patients should be repaired if possible.

The musculoskeletal manifestations of haemophilia: a review of the imaging findings

Haemophilia is a common hereditary cause of bleeding diathesis and the musculoskeletal system is frequently affected. Repeated episodes of haemarthrosis initiate a cascade towards haemophilic arthropathy, a disabling and deforming joint disease with both degenerative and inflammatory features, which include articular cartilage loss, bone erosions, and synovitis. Haemophilic pseudotumour and intra-muscular haematoma make up the remainder of the musculoskeletal manifestations of this systemic condition. Radiological assessment is vital in the assessment and follow-up of these haemophilic complications and MRI is the reference standard. This article summarises the radiological findings relevant to the diagnosis and monitoring of this complex patient group.

Normal meniscal dimensions at different patient ages-MRI evaluation

OBJECTIVE

The purpose of this work is to evaluate the normal meniscal and tibial dimensions in relation to age and gender in different children using conventional MRI sequences.

MATERIALS AND METHODS

Morphometric measurements of the menisci were retrospectively performed on knee MRIs of children (< 18 years). All knee MRIs over a 7-year period were collected. Exclusion criteria included: prior knee surgery or diseases involving the knee joint. A total of 186 children were included, 110 boys and 76 girls, with a mean age of 8.2 years (range, 0.3-17.8 years). Menisci and tibial measurement changes with age and gender as well as differences between the medial and lateral menisci were evaluated.

RESULTS

The medial menisci measurements increased with age (p value < 0.001). The lateral menisci measurements increased with age (p value < 0.001), except for the coronal meniscal width (p = 0.084). Coronal and sagittal percentage of meniscal coverage of the tibia decreased with age (p < 0.001). Medial menisci have greater sagittal width and anterior horn height than lateral menisci (p value < 0.001). Lateral menisci are larger in their coronal width and height, and sagittal posterior horn height in comparison to medial menisci (p < 0.001).

CONCLUSIONS

Menisci increase in all dimensions in correlation with age; except in the coronal meniscal width, which is a useful dimension to diagnose discoid meniscus on MRI, based on this, it would seem that the currently published size criteria, based on adults, could be applicable to children. The tibia has a faster rate dimension increase in correlation with age in comparison to the menisci.

A modified tibial compression test for the detection of meniscal injury in dogs

OBJECTIVE

To assess diagnostic efficacy of a modified tibial compression test in predicting medial meniscal injury in dogs with cranial cruciate ligament failure.

METHODS

Dogs admitted for surgical stabilisation of stifles with cranial cruciate ligament failure were examined by five preoperative physical tests to assess medial meniscal injury. Results of each physical test were compared with findings at arthrotomy and used to calculate sensitivities, specificities, positive and negative predictive values.

RESULTS

None of the physical tests were accurate in reflecting meniscal integrity for dogs with cranial cruciate failure. Out of the five tests, the modified tibial compression test exhibited the highest concordance and sensitivity for the detection of medial meniscal tears. A palpable click during the modified tibial compression test had a sensitivity and specificity up to 63 and 77%, respectively, for the detection of medial meniscal lesions. Concordance values were up to 40% for the modified tibial compression test, followed by the range of motion test (up to 25%), while all other physical tests had concordance values below 10%.

CLINICAL SIGNIFICANCE

Physical tests are highly available, affordable and can be easily performed, but their efficacy in diagnosing medical meniscal injury is low. Meniscal clicks associated with meniscal tears were more frequently elicited during the modified tibial compression test when compared with other traditional tests.

Accuracy of MRI evaluation of meniscus tears in the setting of ACL injuries

BACKGROUND

Our purpose was to evaluate the diagnostic performance of magnetic resonance imaging (MRI) for the pre-operative detection of meniscus tears requiring operative intervention, and identify factors that determined accuracy of diagnosing meniscus tears, in the setting of anterior cruciate ligament (ACL) reconstruction.

METHODS

Patients who underwent primary ACL reconstruction were retrospectively reviewed. A meniscus tear was classified as requiring treatment if it was debrided or repaired at the time of ACL reconstruction. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of pre-operative MRIs were determined for medial and lateral meniscus tears.

RESULTS

Sensitivity, specificity, PPV, and NPV of MRI were 0.90, 0.75, 0.58, and 0.95 for medial meniscus tears, respectively, and 0.67, 0.81, 0.65, and 0.82 for lateral meniscus tears. MRI-diagnosed medial meniscus tears were associated with a longer time interval between initial injury and imaging compared to ACL tears without concomitant meniscus injury on MRI (p=0.038). Vertical medial meniscus tears were less likely than other tear patterns to require treatment at the time of ACL reconstruction (p=0.03). MRI showed a higher diagnostic performance for lateral meniscus tears when surgery was performed within 30days of imaging.

CONCLUSIONS

This study demonstrates only moderate sensitivity and specificity of pre-operative MRI in the detection of meniscus tears requiring operative treatment in the setting of ACL injury. High rates of false diagnoses were observed, suggesting MRI may not be as accurate in predicting positive or negative meniscus findings at the time of ACL reconstruction as previously reported.

LEVEL OF EVIDENCE

Level III.

Reporting knee meniscal tears: technical aspects, typical pitfalls and how to avoid them

Magnetic resonance imaging (MRI) is the most accurate imaging technique in the diagnosis of meniscal lesions and represents a standard tool in knee evaluation. MRI plays a critical role in influencing the treatment decision and enables information that would obviate unnecessary surgery including diagnostic arthroscopy. An accurate interpretation of the knee depends on several factors, starting with technical aspects including radiofrequency coils, imaging protocol and magnetic field strength. The use of dedicated high-resolution orthopaedic coils with a different number of integrated elements is mandatory in order to ensure high homogeneity of the signal and high-resolution images. The clinical imaging protocol of the knee includes different MRI sequences with high-spatial resolution in all orientations: sagittal, coronal, and axial. Usually, the slice thickness is 3 mm or less, even with standard two-dimensional fast spin echo sequences. A common potential reason for pitfalls and errors of interpretation is the unawareness of the normal tibial attachments and capsular attachment of the menisci. Complete description of meniscal tears implies that the radiologist should be aware of the patterns and the complex classification of the lesions.

TEACHING POINTS

• Technical factors may influence MRI interpretation. • Unawareness of the normal meniscal anatomy may lead to errors of interpretation. • Description of meniscal tears implies the knowledge of meniscal tear classification.

Meniscal pathology in children: differences and similarities with the adult meniscus

The normal meniscus undergoes typical developmental changes during childhood, reaching a mature adult appearance by approximately 10 years of age. In addition to recognizing normal meniscal appearances in children, identifying abnormalities - such as tears and the different types of discoid meniscus and meniscal cysts, as well as the surgical implications of these abnormalities - is vital in pediatric imaging. The reported incidence of meniscal tears in adolescents and young adults has increased because of increased sports participation and more widespread use of MRI. This review discusses the normal appearance of the pediatric meniscus, meniscal abnormalities, associated injuries, and prognostic indicators for repair.

Magnetic resonance imaging and arthroscopic appearance of the menisci of the knee

The menisci are critical for normal function of the knee, providing shock absorption and load transmission that reduce stress on the articular cartilage. When torn, a meniscus may require surgery to restore function, reduce pain, and eliminate mechanical symptoms. Patterns of meniscal tears include longitudinal and bucket-handle, which are often reparable; and horizontal, radial, vertical flap, horizontal flap, and complex. Root tears are usually radial and occur in the posterior roots. When reviewing magnetic resonance images, one must be aware of normal variants and imaging pitfalls that may simulate pathology.

Meniscal injuries and imaging the postoperative meniscus

Meniscal injuries are common. Magnetic resonance imaging is considered the imaging modality of choice in diagnosing meniscal pathologic conditions in the nonoperative knee. Meniscal-preserving surgery is becoming more frequent, with a resultant increase in postoperative meniscal imaging, which is particularly challenging for the reporting radiologist. This article provides a review of the anatomy, pathologic conditions, and diagnostic pitfalls of meniscal injury, with a synopsis of the issues faced with postoperative meniscal imaging.

Normal MR imaging anatomy of the knee

Magnetic resonance (MR) imaging is the preferred imaging modality for evaluating internal derangement of the knee, due to its superior soft tissue contrast resolution, multiplanar imaging capability, and lack of ionizing radiation. The superb image quality facilitates learning of normal imaging anatomy and conceptualizing spatial relationships of anatomic structures, leading to improved understanding of pathologic processes, mechanisms of injury, and injury patterns, and ultimately increased diagnostic accuracy. This article depicts normal MR imaging anatomy and commonly encountered anatomic variants using representative MR images of the knee, and describes and explains the rationale of routine knee MR imaging protocol.

Diagnostic imaging of the canine stifle: a review

The stifle joint, a common location for lameness in dogs, is a complex arrangement of osseous, articular, fibrocartilaginous, and ligamentous structures. The small size of its component structures, restricted joint space, and its intricate composition make successful diagnostic imaging a challenge. Different tissue types and their superimposition limit successful diagnostic imaging with a single modality. Most modalities exploit the complexity of tissue types found in the canine stifle joint. Improved understanding of the principles of each imaging modality and the properties of the tissues being examined will enhance successful diagnostic imaging.

Effects of medial meniscus posterior horn avulsion and repair on tibiofemoral contact area and peak contact pressure with clinical implications

BACKGROUND

Avulsion of the posterior horn attachment of the medial meniscus can compromise load-bearing ability, produce meniscus extrusion, and result in tibiofemoral joint-space narrowing, articular cartilage damage, and osteoarthritis.

HYPOTHESIS

Avulsion of the posterior horn of the medial meniscus will increase peak contact pressure and decrease contact area in the medial compartment of the knee, and posterior horn repair will restore contact area and peak contact pressures to values of the control knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen human cadaveric knees had tibiofemoral peak contact pressures and contact area measured in the control state. The posterior horn of the medial meniscus was avulsed from its insertion and knees were retested. The meniscal avulsion was repaired by suture through a transosseous tunnel and the knees were tested a third time.

RESULTS

Avulsion of the posterior horn attachment of the medial meniscus resulted in a significant increase in medial joint peak contact pressure (from 3841 kPa to 5084 kPa) and a significant decrease in contact area (from 594 mm(2) to 474 mm(2)). Repair of the avulsion resulted in restoration of the loading profiles to values equal to the control knee, with values of 3551 kPa for peak pressure and 592 mm(2) for contact area.

CONCLUSION

Posterior horn medial meniscal root avulsion leads to deleterious alteration of the loading profiles of the medial joint compartment and results in loss of hoop stress resistance, meniscus extrusion, abnormal loading of the joint, and early knee medial-compartment degenerative changes.

CLINICAL RELEVANCE

The repair technique described restores the ability of the medial meniscus to absorb hoop stress and eliminate joint-space narrowing, possibly decreasing the risk of degenerative disease.

Arthroscopic and magnetic resonance imaging evaluation of meniscus lesions in the chronic anterior cruciate ligament-deficient knee

PURPOSE

We performed this prospective study to evaluate the incidence of meniscus tears arthroscopically and the effectiveness of magnetic resonance imaging (MRI) in detecting these lesions in patients with chronic anterior cruciate ligament (ACL)-deficient knees.

METHODS

We reviewed 50 patients (46 male and 4 female) with a mean age of 27 years (range, 18 to 48 years) who underwent ACL reconstruction for chronic ACL tears. Injuries were classified as chronic because arthroscopy was performed after more than 6 weeks of injury. All 50 patients had clinical and MRI evaluation followed by knee arthroscopy. The MRI and arthroscopic findings were then analyzed by a single independent reviewer. The presence of meniscus tears and their morphologic types and locations were analyzed. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI were calculated.

RESULTS

On arthroscopy, a medial meniscus tear was found in 18 patients (36%), a lateral meniscus tear was found in 11 patients (22%), both menisci were torn in 8 patients (16%), and no meniscus lesion was found in 13 patients (26%). The most common morphologic type of tear seen in the medial meniscus was "complex" (n = 11 [42%]), and that in the lateral meniscus was "longitudinal" (n = 10 [53%]). The posterior horn of the meniscus was the most common tear site. The overall sensitivity, specificity, positive predictive value, and negative predictive value for detecting meniscus tears in chronic ACL-deficient knees on MRI were 90%, 89%, 87%, 93%, respectively.

CONCLUSIONS

We conclude from our study that in chronic ACL-deficient patients, the prevalence of posterior horn medial meniscus tears seems to be high. Anterior horn tears and radial and horizontal patterns of meniscus tears seem to be rare in chronic ACL deficiency. MRI correlates well with arthroscopy and has high negative predictive values.

LEVEL OF EVIDENCE

Level I, prognostic prospective study.

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.

MR diagnosis of meniscal tears of the knee: analysis of error patterns

PURPOSE

Despite high accuracy of magnetic resonance imaging (MRI) for diagnosing meniscal tears, MR findings do not always agree with surgical findings. We performed a blinded, retrospective study to analyze the nature and frequency of errors in the MR diagnosis of meniscal tears.

MATERIALS AND METHODS

Medical records of 100 consecutive patients who underwent MR and arthroscopy of the knee at our institution were reviewed. Twelve patients underwent prior meniscal surgery. Twenty-three patients had 27 discrepancies between MR and surgical findings. These were independently reviewed by two additional musculoskeletal radiologists in a double blinded fashion. Original incorrect diagnoses were categorized as either unavoidable, interpretation error or equivocal for meniscal tear.

RESULTS

MR accuracy was 88% for the medial and 85% for the lateral meniscus. Of 27 incorrect MR diagnoses, 12 (44%) were unavoidable, 10 (37%) equivocal and 5 (19%) interpretation errors. Of the 67 medial meniscal tears, 12 (18%) were missed. Eight (67%) of these 12 were categorized as equivocal, including three postoperative menisci. Of 30 lateral tears, 12 (40%) were missed, 7 (58%) of which were categorized as unavoidable. Of these 12, 11 (92%) showed fraying of the inner edge, which was shaved at arthroscopy (n = 8) or had stable tear treated conservatively (n = 3). There were three false-positive diagnoses, all occuring in the lateral meniscus, two of which were unavoidable and one interpretation error.

CONCLUSION

Of all missed lateral meniscal tears, most are unavoidable and related to confusion between what represents fraying and what represents a tear. Unavoidable false-positive diagnoses are infrequent and may be related to incomplete arthroscopic evaluation. Subtle or equivocal findings still make MR diagnosis difficult, even for experienced radiologists.

Follow-up of collagen meniscus implants by MRI

PURPOSE

The purpose of our study was to evaluate the usefulness of magnetic resonance imaging (MRI) in the follow-up of patients treated with collagen meniscus implant (CMI) and to identify MRI patterns suitable for defining its evolution.

MATERIALS AND METHODS

Between March 2001 and June 2003, CMI was performed on 40 patients (27 men and 13 women, age 23-58 years, median 41 years) affected by irreparable medial meniscal lesions. All patients underwent MRI follow-up at 6 months and 1 year and 16 patients 2 years after the operation; 12 patients underwent second-look arthroscopy with implant biopsy. All MRI examinations were performed with a 1.5-T unit using GE T2*, spin-echo (SE) T1, and FatSat fast spin-echo (FSE) DP and T2-weighted sequences, with different orientations. At 24 months, MR arthrography was also performed. Implant evolution was assessed on the basis of MRI direct and indirect criteria. Direct criteria were morphology and signal intensity of the collagen meniscus/residual meniscus complex. Based on these characteristics, three pattern were identified and classified from 1 to 3, where a higher score corresponded to characteristics approaching those of the normal meniscus. Indirect criteria were chondral surface and subchondral bone marrow oedema at implant site and associated synovial pathology.

RESULTS

MRI follow-up at 6 months showed CMI shape and size to be normal (type 3) in 35/40 patients and type 2 in 5/40 patients. CMI signal intensity was type 1 in 32/40 patients and type 2 in 8/40. An interface between prosthetic and native meniscus was identified in 27/40 patients. Chondral lesions were present in 3/40 cases and subchondral bone marrow oedema in 8/40 cases. Reactive synovial effusion was seen in 2/40 patients. MRI follow-up at 12 months showed CMI shape and size to be normal (type 3) in 33/40 patients and type 2 in 7/40. Signal intensity was type 1 in 14/40 patients and type 2 in 26/40 patients. The interface was seen in 19/40 patients. The associated chondral lesions were unchanged, whereas subchondral bone marrow oedema was present in 3/40 patients. No synovial reaction was detected. At 24 months, CMI size was type 3 in 9/16 patients, type 2 in 6/16, and type 1 in one patient in whom the implant could not be identified, as it had been totally resorbed. CMI signal intensity was type 2 in 11/15 and type 3 in 4/16. The interface was identified in seven patients. MR arthrography depicted two additional chondral lesions and enabled correct grading of all lesions. Subchondral bone marrow oedema was present in two patients only.

CONCLUSIONS

MRI enables morphological and structural changes of CMI to be monitored over time. Follow-up can be extended beyond 2 years, until the CMI has stabilised and subchondral bone marrow oedema has completely resolved. In the single case with a poor CMI outcome, no related direct or indirect signs were identified.

LOW-FIELD MRI AND ARTHROSCOPY OF MENISCAL LESIONS IN TEN DOGS WITH EXPERIMENTALLY INDUCED CRANIAL CRUCIATE LIGAMENT INSUFFICIENCY

Little is known about the magnetic resonance imaging (MRI) appearance of canine meniscal lesions. The aim of this study is to describe the MR appearance of meniscal lesions in dogs with experimentally induced cranial cruciate ligament (CCL) deficiency. The pilot study revealed dogs weighing approximately 10 kg to be too small for meniscal evaluation on low-field MRI. In the main study, dogs weighing approximately 35 kg were used. The left CCL was transected and low-field MRI was performed regularly until 13 months post-surgery. Normal menisci were defined as grade 0. Intrameniscal lesions not reaching any surface corresponded to grade 1 if focal and to grade 2 if linear or diffuse. Grade 3 lesions consisted in linear tears penetrating a meniscal surface. Grade 4 lesions included complex signal changes or meniscal distortion. Between 2 and 13 months post-surgery, all dogs developed grade 4 lesions in the medial meniscus. Most of them corresponded to longitudinal or bucket handle tears on arthroscopy and necropsy. Two dogs showed grade 3 lesions reaching the tibial surface of the lateral meniscus on MRI but not in arthroscopy. Such tears are difficult to evaluate arthroscopically; MRI provides more accurate information about the tibial meniscal surface. Grades 1 and 2 lesions could not be differentiated from presumably normal menisci with our imaging technique. An MRI grading system better adapted to canine lesions has yet to be developed. MRI is a helpful tool for the diagnosis of complete tears in the canine meniscus, especially in larger dogs.

Medial meniscus posterior root attachment injury and degeneration: MRI findings

The posterior root attachment of the medial meniscus is readily identifiable on MRI. Unless specifically reviewed, injuries involving this structure may be overlooked. Significant meniscal root pathology may cause functional incompetence of the meniscus, with consequent early onset cartilage degeneration and osteoarthritis. This review article emphasizes the importance of positive identification of an intact meniscal root and illustrates the known association of meniscal root injury or tear with medial extrusion of the medial meniscus by greater than 3 mm beyond the joint margin.

MRI of menisci repaired with bioabsorbable arrows

OBJECTIVE

To analyze with conventional magnetic resonance imaging (MRI) the signal appearance of menisci repaired with bioabsorbable arrows.

DESIGN AND PATIENTS

Forty-four patients with 47 meniscal tears treated with bioabsorbable arrows underwent follow-up conventional MRI examination. The time interval between the surgery and MRI varied from 5 to 67 months (mean 26 months). Twenty-six patients also had concurrent repair of torn anterior cruciate ligament. The following grades were used to classify meniscal signal intensity: (a) G0; low signal intensity on all sequences and regular configuration in every plane, (b) G1; increased signal intensity within the meniscus, not extending to the meniscal surface, (c) G2; increased signal intensity linear in shape, which may or may not communicate with the capsular margin of the meniscus, without extending to the meniscal surface, and (d) G3; increased signal intensity extending to the meniscal surface.

RESULTS

Thirteen menisci (27.5%) had normal signal intensity, 13 menisci (27.5%) Grade 1 signal intensity, 9 menisci (19%) Grade 2 signal intensity and 12 menisci (26%) Grade 3 signal intensity. The time difference between operation and MRI was statistically significant between the G0 (36 months) and G3 groups (14 months; P = 0.0288). There was no statistical significance in different grades between medial and lateral meniscus or between patients with operated or intact ACL. On physical examination sixteen patients reported slight symptoms, seen evenly in each group.

CONCLUSION

No difference was seen in different grades between patients with operated or intact ACL. The highest incidence of menisci with a Grade 3 signal was seen in patients where surgery was within the last 18 months.

Orthopedic trauma: office management of major joint injury

Orthopedic injuries are common reasons for visits to primary care physicians. Careful history and physical examination with intelligent use of imaging technology will arrive at the correct diagnosis in most patients. Many conditions may be definitively managed by the office internist. Others maybe initially stabilized and referred to orthopedic surgeons for definitive care. Nondisplaced fractures, tendon injuries, sprains, and overuse syndromes are entities within the purview of the primary care physician. Familiarity and confidence with diagnosis and management of these conditions in the office is optimal for the care of the adult patient.

Characteristics of Displaceable and Nondisplaceable Meniscal Tears at Kinematic MR Imaging of the Knee

PURPOSE

To prospectively determine if kinematic magnetic resonance (MR) imaging of the knee may demonstrate displacement of menisci with tears and, if so, to characterize displaceable and nondisplaceable meniscal tears.

MATERIALS AND METHODS

The study was approved by the hospital's review board, and informed consent was obtained. Forty-two patients (30 men, 12 women; mean age, 36.9 years) with 43 arthroscopically documented meniscal tears visible at 1.5-T MR imaging underwent kinematic MR imaging with an open-configuration 0.5-T MR imager with their knees in supine neutral, supine with 90 degrees flexion and external or internal rotation, and upright weight-bearing positions. Analysis of meniscal movement was performed in different knee positions in the coronal MR imaging plane. Meniscal displacement--that is, meniscal movement of 3 mm or more (in the medial direction for the medial meniscus, in the lateral direction for the lateral meniscus)--was compared with the patient's pain level as assessed with a visual analog scale by using analysis of variance.

RESULTS

Between the different knee positions, meniscal displacement of 3 mm or more (displaceable meniscal tears) was noted in 18 (42%) of 43 menisci with tears. Simultaneous occurrence of grade II or III ipsilateral collateral ligament lesions was present in all 18 displaceable meniscal tears, whereas a normal-appearing collateral ligament or collateral ligament lesion (grade I) was present in 22 of 25 nondisplaceable tears (P < .05). Displaced menisci most commonly had complex, radial, or longitudinal tear configurations (16 of 18, 89%). Patients with displaceable meniscal tears had significantly more pain than did patients with nondisplaceable meniscal tears (P < .001), independent of the concomitant knee abnormalities.

CONCLUSION

Displaceable meniscal tears usually have longitudinal, radial, or complex configurations; such tears are associated with substantial ipsilateral collateral ligament lesions and pain.

Patients with suspected meniscal tears: prevalence of abnormalities seen on MRI of 100 symptomatic and 100 contralateral asymptomatic knees

OBJECTIVE

The purpose of this study was to evaluate the prevalence of MR abnormalities of the knee on the symptomatic and contralateral asymptomatic sides in patients with suspected meniscal tears. SUBJECTS AND METHODS. One hundred patients (mean age, 42.7 years; range, 18-73 years) referred for suspected meniscal tears were prospectively examined with MRI of both knees when the contralateral knee was asymptomatic. The prevalence of various types of meniscal tears and other MR abnormalities was determined.

RESULTS

Meniscal tears were found in 57 symptomatic knees and in 36 contralateral asymptomatic knees. In those 57 patients with a meniscal tear on the symptomatic side, the prevalence of asymptomatic tears in the contralateral side was 63% (36/57). Horizontal or oblique meniscal tears were found medially in 32 and laterally in 11 symptomatic knees, and medially in 29 and laterally in eight asymptomatic knees. Radial, vertical, complex, or displaced tears were found medially in 18 and laterally in five symptomatic knees, and medially in five and laterally in none of the asymptomatic knees. Collateral ligament abnormalities were found in 53 symptomatic knees and in six asymptomatic knees. Pericapsular soft-tissue abnormalities were found in 64 symptomatic and in 12 asymptomatic knees. Edema-like bone marrow abnormalities were found in 36 symptomatic and in three asymptomatic knees.

CONCLUSION

Horizontal or oblique meniscal tears are frequently encountered in both asymptomatic and symptomatic knees and may not always be related to symptoms. However, radial, vertical, complex, or displaced meniscal tears and abnormalities of the collateral ligaments, pericapsular soft tissues, and bone marrow are found almost exclusively on the symptomatic side and appear to be clinically more meaningful.