Meniscal tears of the knee: accuracy of MR imaging

Three-tesla MR imaging of the knee

Three-tesla MR imaging of the knee allows for fast, accurate high-resolution imaging. Three-tesla MR imaging is highly accurate in detection of meniscal tears. This detection aids referring physicians, because if a meniscal tear is not seen on three-tesla MR imaging, it is highly unlikely to be present. High field imaging allows for three-dimensional imaging of the knee. Referring doctors have found this "virtual arthroscopy" to be useful in presurgical planning.

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.

The diagnosis of meniscus tears: the role of MRI and clinical examination

Magnetic resonance imaging (MRI) and clinical examination are tools commonly used in the diagnosis of meniscus tears. It has been suggested routine MRI before therapeutic arthroscopy for clinically diagnosed meniscus tears will reduce the number and cost of unnecessary invasive procedures. We designed a systematic review of prospective cohort studies comparing MRI and clinical examination to arthroscopy to diagnosis meniscus tears. Thirty-two relevant studies were identified by a literature review. Careful evaluation by an experienced examiner identifies patients with surgically treatable meniscus lesions with equal or better reliability than MRI. MRI is superior when indications for arthroscopy are solely diagnostic. However, the methods by which such a clinician arrives at a conclusion have not been identified. To create an evidence-based algorithm for the diagnosis of a meniscus tear future investigations should prospectively assess the value of commonly used aspects of the patient history and meniscus tests. MRI is useful, but should be reserved for situations in which an experienced clinician requires further information before arriving at a diagnosis. Indications for arthroscopy should be therapeutic, not diagnostic in nature.

Use of the "two-slice-touch" rule for the MRI diagnosis of meniscal tears

OBJECTIVE

We reviewed our experience with knee MRI to determine if using the "two-slice-touch" rule increased our positive predictive value for diagnosing meniscal tears. This rule classifies a meniscus as torn if there are two or more MR images with abnormal findings and as possibly torn if there is only one MR image with an abnormal finding. We also compared our sensitivity and specificity using fast spin-echo imaging with previously reported studies.

MATERIALS AND METHODS

We reviewed the medical records of 174 patients who had knee MR examinations and correlative knee arthroscopy to determine our accuracy when we diagnosed menisci as torn, possibly torn, or intact using knee arthroscopy as the gold standard.

RESULTS

Our positive predictive value increased from 91% to 94% (p = 0.37) for medial meniscal tears and from 83% to 96% (p = 0.02) for lateral meniscal tears when using the two-slice-touch rule compared with the standard criterion of diagnosing a meniscus as torn if one or more images are abnormal. When using the standard criterion, we had 95% sensitivity and 85% specificity for diagnosing medial meniscal tears and 77% sensitivity and 89% specificity for diagnosing lateral meniscal tears.

CONCLUSION

When using the two-slice-touch rule, we had an increased positive predictive value for diagnosing menisci as torn, which was statistically significant for the lateral meniscus. Our accuracy using the standard criterion with fast spin-echo imaging was comparable to that reported in previous studies with spin-echo imaging.

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.

3.0-T MRI of meniscal tears

OBJECTIVE

The sensitivity and specificity of 3.0-T MRI of the knee for meniscal tears have not been specifically assessed. We undertook a retrospective review of 100 consecutive MR examinations of the knee followed by arthroscopy to evaluate the sensitivity and specificity of 3.0-T MRI compared with arthroscopy in the detection of meniscal tears.

MATERIALS AND METHODS

Two experienced musculoskeletal radiologists retrospectively reviewed MR scans of the knees of 100 patients who underwent consecutive knee arthroscopic procedures after MRI examinations. Interpretations were performed by consensus review with the reviewers blinded to arthroscopic results at the time of consensus review. All patients underwent complete MRI of the knee on a 3.0-T unit. All patients underwent fast spin-echo proton density sagittal imaging at 2-mm slice thickness. Fat-saturated fast spin-echo T2 axial, coronal, and sagittal imaging and T1 coronal imaging also were performed. All 100 patients underwent arthroscopy, and the results were compared with MR interpretations.

RESULTS

Consensus retrospective review of the 100 knee MR examinations revealed 111 meniscal tears. Four meniscal tears seen on arthroscopy were not seen on MR examination. There were three false-positive MR interpretations of meniscal tear compared with arthroscopy. In this study, the sensitivity of MRI in the detection of meniscal tears was 96%, and the specificity was 97%.

CONCLUSION

MRI of the knee at 3.0 T is sensitive and specific compared with arthroscopy in the detection of meniscal tears. Findings at 3.0 T compare favorably with results at 1.5-T or lower field strength.

Magnetic resonance arthrography

For decades, fluoroscopic arthrography was the only method available to image a joint with contrast enhancement. Advances in CT led to the natural development of CT arthrography. Development of MRI and its capability for multiplanar imaging led to direct magnetic resonance arthrography (MRA). This technique has been performed since 1987 and has surpassed CT arthrography in popularity in the United States. Indirect MRA developed subsequently to offer a less invasive alternative. This article presents an overview of direct MRA and addresses joint-specific issues regarding direct MRA. An overview of indirect MRA also is provided.

MRI and non-cartilaginous structures in knee osteoarthritis

Magnetic resonance imaging (MRI) provides a sensitive tool for examining all the structures involved in the osteoarthritis (OA) process. While much of the MRI literature previously focussed on cartilage, there is increasing research on whole-organ evaluation and including features such as synovitis, bone marrow edema, and meniscal and ligamentous pathology. The aim of this session at the Outcome Measures in Rheumatology Clinical Trials (OMERACT)-Osteoarthritis Research Society International (OARSI) Workshop for Consensus in Osteoarthritis Imaging was to describe the current MRI methods for identifying and quantifying non-cartilaginous structures and review their associations with both OA symptoms and structural progression. Although there is much experience in measuring synovitis (derived from the rheumatoid arthritis literature), only one study has reported an association of MRI-detected synovitis and effusions with OA pain. Bone marrow edema lesions, which may represent areas of trabecular remodelling, have been associated with pain and compartment-specific structural deterioration. MRI studies have confirmed the frequency and importance of meniscal damage in progressive cartilage loss, but not related such damage to symptoms. Osteophytes have been associated with cartilage loss and malalignment to the side of the osteophyte. Ligament damage, including anterior cruciate ligament tears, has been found more commonly than expected in painful OA knees. Improvements in quantitative and semi-quantitative assessments of non-cartilage features will greatly assist understanding of the OA process and its response to therapy.

Postoperative Imaging of the Knee

The knee is a frequently injured joint and, thus, a common focus of operative intervention. As operative techniques and imaging modalities evolve, radiologists must be aware of the expected postoperative appearance after knee surgeries that are performed commonly and also must be comfortable recognizing complications encountered commonly in the immediate and delayed postoperative period. Drawing on the large amount of attention this subject has received of late in the radiologic and orthopedic literature, this article reviews the knee surgeries performed most commonly and the expected normal and most frequently encountered abnormal postoperative imaging findings with an emphasis on MR imaging.

The value of sonography with micro convex probes in diagnosing meniscal tears compared with arthroscopy

OBJECTIVE

Meniscal tears are common in knee injuries. Sonography has been used in the knee to evaluate meniscal tears. Linear probes with high resolution have been used, and the overall accuracy of sonography has been more than 70% in many studies. In this study, we used a 6.5-MHz micro convex probe to evaluate meniscal tears, and the results were compared with arthroscopic findings.

METHODS

Four hundred six knee joints with knee pain and a clinical indication for arthroscopy were examined from the popliteal fossa with the 6.5-MHz micro convex probe. Those patients with positive sonographic findings who had an arthroscopic examination (100 patients) were included in our study, and the results were compared. The results were statistically analyzed by the Fisher exact test.

RESULTS

One hundred knees with sonographic examinations underwent arthroscopic evaluation. Three age groups were included in the study (20-30, 30-40, and >40 years). Comparison of the results between the two methods showed sensitivity of 100% and specificity of 95% for sonography in detecting meniscal tears. The positive predictive value for the medial meniscus was 95%, and the negative predictive value was 100%; these values for the lateral meniscus were 93% and 100%, respectively.

CONCLUSIONS

Meniscal tears are common in all age groups. The use of sonography allows rapid, low-cost, and noninvasive exploration of meniscal tears as a first-line diagnostic method. We recommend high-resolution micro convex probes, which better fit the anatomic concavity of the popliteal fossa, as efficient investigation tools.

Clinical Course of Knees with Asymptomatic Meniscal Abnormalities: Findings at 2-year Follow-up after MR Imaging–based Diagnosis

PURPOSE

To prospectively evaluate the clinical course of asymptomatic meniscal lesions diagnosed by using magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. The clinical courses of meniscal lesions in 84 asymptomatic knees (in 48 men and 36 women; mean age, 43.6 years; age range, 18-73 years) were assessed. Thirty-one asymptomatic meniscal lesions were depicted among the 84 knees at MR imaging. The follow-up period was at least 2 years (mean, 29.8 months; range, 24-36 months). Knee pain, stiffness, and function during daily and sports activities were assessed by using a visual analogue scale (VAS), on which a score of 0 indicated no pain or complaints and a score of 100 indicated maximal pain and/or complaints. The chi2 test was used for statistical analysis.

RESULTS

At follow-up, 12 (39%) of the 31 patients with and 10 (19%) of the 53 patients without meniscal lesions reported having knee pain (P = .046). Nine (29%) patients with and five (9%) patients without meniscal lesions reported having knee stiffness (P = .02). Ten (32%) patients with and five (9%) patients without meniscal lesions reported having impaired function during daily activities (P = .008). Thirteen (42%) patients with and 15 (28%) patients without meniscal lesions reported having impaired function during sports activities (P = .20). Mean VAS scores ranged from 22 to 30; mean VAS scores for pain, stiffness, impaired daily function, and impaired sports function were 26, 22, 27, and 30, respectively. None of the initially asymptomatic knees was treated with surgery during the follow-up period.

CONCLUSION

The clinical course of knees with initially asymptomatic meniscal lesions, compared with the clinical course of knees without meniscal lesions, is characterized by an increased frequency of complaints. However, severities of pain and knee function impairment remain low.

The use of axial reconstructed images from three-dimensional MRI datasets for morphological diagnosis of meniscal tears of the knee

INTRODUCTION

In recent years, three-dimensional (3D) MRI has been utilized to detect meniscal tears and has displayed several advantages over 2D MRI. The diagnostic performance to discriminate the type of meniscal tears by 2D MRI (sagittal and coronal images) and axial images from 3D MRI datasets has not been reported yet. The aim of the present study is to evaluate the efficacy of the axial reconstructed images from 3D MRI datasets for the morphological diagnosis of meniscal tears of the knee.

MATERIALS AND METHODS

Seventy-four menisci in 37 patients who underwent arthroscopic surgery of the knee were studied. All patients were examined by 2D sagittal and coronal MRI and by axial images from 3D MRI datasets prior to surgery. First, we compared the diagnostic performance for meniscal tears by 2D sagittal and coronal MRI to that by axial images from 3D MRI datasets as judged by arthroscopic findings. Second, we compared the correlation of tear types presumed from 2D sagittal and coronal MRI to arthroscopy with those presumed from axial images from 3D MRI datasets to arthroscopy.

RESULTS

For the diagnostic performance of meniscal tears on 2D MRI, the sensitivity, specificity and accuracy were 93.5%, 88.4% and 90.5%, respectively. On axial images from 3D MRI, the sensitivity, specificity and accuracy were 96.8%, 79.1% and 86.5%, respectively. Nine cases were false-positive on axial images, while 5 cases were false-positive on 2D images. Correlations to arthroscopy were 100% by both scans for longitudinal tears and discoid meniscus tears. Only 29% were correctly diagnosed by 2D sagittal and coronal images for radial tears, however, all radial tears could be correctly diagnosed by axial images. All horizontal tears were correctly diagnosed on 2D sagittal and coronal images, while none of the horizontal tears could be correctly diagnosed from axial images.

CONCLUSION

Axial images from 3D MRI datasets were useful in the diagnosis of radial tears, but two limitations are noted concerning the use of axial images. First, medial menisci should be carefully read on axial slices because of the relatively high rate of false-positives on medial menisci. Second, axial images cannot discriminate horizontal tears from other types of meniscus tears.

Osteoarthritis of the knee: comparison of MR imaging findings with radiographic severity measurements and pain in middle-aged women

PURPOSE

To prospectively compare magnetic resonance (MR) imaging-defined abnormalities of osteoarthritis (OA) of the knee with radiographic severity measurements of OA of the knee and self-reported pain.

MATERIALS AND METHODS

This study was approved by the institutional review board of University of Michigan. Informed consent was obtained for this HIPAA-compliant study. Knee MR imaging was performed in 117 women (mean age, 46 years; range, 32-56 years) from a community-based arthritis study (n = 1053) with 30 women in each of four categories: (a) no pain and no OA of the knee, (b) no pain and OA of the knee, (c) pain and no OA of the knee, and (d) pain and OA of the knee. OA of the knee was defined from radiographs. Two hundred thirty-two eligible knees had Kellgren-Lawrence scores for OA of the knee as follows: grade 0, 115 (49.6%); grade 1, 33 (14.2%); grade 2, 66 (28.4%); grade 3, 17 (7.3%); and grade 4, one (0.4%). MR images were assessed for location and severity of defects of cartilage, bone marrow edema (BME), osteophytes, subchondral cysts, sclerosis, meniscal and/or ligamentous tears, joint effusion, synovial cysts, and synovitis. MR imaging findings were compared with radiographic severity of OA of the knee (Kellgren-Lawrence scale) and self-reported pain with analysis of variance, t tests, and contingency table analyses.

RESULTS

Defects of cartilage (higher than grade IIA) were found in 75% of knees; BME was found in 57% of knees (<1 cm, 41%; >1 cm, 16%). Large BME lesions were common in the pain and OA of the knee group (P = .001); this group was significantly more likely to have defects of cartilage (P = .001); meniscal tears (P = .001); and osteophytes, subchondral cysts, sclerosis, joint effusion, and synovitis (P < .001). Defects of cartilage, osteophytes, sclerosis, meniscal or ligamentous tears, joint effusion, and synovitis were strongly related to increasing Kellgren-Lawrence grade (P < .001).

CONCLUSION

In middle-aged women, there were significant associations between pain, radiographic severity of OA of the knee, and seven MR imaging-identified parameters.

Three-tesla imaging of the knee: initial experience

PURPOSE

To assess 3-T imaging of the knee.

MATERIALS AND METHODS

We reviewed 357 3-T magnetic resonance images of the knee obtained using a dedicated knee coil. From 58 patients who had arthroscopy we determined the sensitivity and specificity for anterior cruciate ligament (ACL) tear and medial and lateral meniscal tear.

RESULTS

A chemical shift artifact showed prominently at 3 T even after improvements had been made by increasing the bandwidth. For complete ACL tear the sensitivity was 100% (95% confidence interval, CI, 75.30-100.00), and the specificity was 97.9% (95% CI 87.7-99.9). For the medial meniscus the sensitivity was 100.00% (95% CI 90.0-100.00), and the specificity was 83.3%(95% CI 66.6-95.3). For the lateral meniscus the sensitivity was 66.7% (95% CI 38.4-88.2), and the specificity was 97.6% (95% CI 87.1-99.9).

CONCLUSIONS

In general 3-T imaging allows a favorable display of anatomy and pathology. The lateral meniscus was assessed to be weaker than the other anatomic structures. Three-tesla imaging allows increased signal-to-noise ratio, increased resolution, and faster scanning times.

Comparison of fast spin-echo versus conventional spin-echo MRI for evaluating meniscal tears

OBJECTIVE

We compare sensitivities of conventional spin-echo and fast spin-echo sequences in the evaluation of meniscal tears. Furthermore, we reevaluate the results from prior studies comparing these two sequences to understand why there are differing conclusions regarding the efficacy of fast spin-echo sequences as a commensurate replacement for conventional spin-echo sequences.

MATERIALS AND METHODS

We used records from a control group of 64 patients (128 menisci) who had undergone arthroscopy to determine the sensitivity of conventional spin-echo sequences for detecting meniscal tears. Two hundred sixteen consecutive patients (432 menisci) were then imaged using conventional spin-echo and fast spin-echo sequences to evaluate for meniscal tears. Both sequences were proton density-weighted with fat suppression.

RESULTS

Of the 432 menisci, 170 tears were detected on conventional spin-echo imaging. Only 128 tears were detected on the fast spin-echo sequence. The sensitivities of conventional spin-echo and fast spin-echo imaging were found to be 93% and 80%, respectively. In addition, findings from conventional spin-echo and fast spin-echo sequences were discordant for 72 menisci (17%, p < 0.01).

CONCLUSION

The sensitivities of conventional spin-echo and fast spin-echo imaging for detecting meniscal tears have been shown to be greater than 90% and approximately 80%, respectively. However, some authors advocate substituting conventional spin-echo imaging with fast spin-echo imaging. We urge the abandonment of fast spin-echo imaging for evaluating meniscal tears because a loss of greater than 10% in sensitivity is unacceptable.

Altered signal intensity in the posterior horn of the medial meniscus: an MR finding of questionable significance

INTRODUCTION

MR imaging has emerged as an important modality in the non-invasive evaluation of osseous and soft-tissue structures in the post-traumatic knee. However, it is sometimes impossible to determine with confidence if a focus of high signal intensity in the meniscus is confined to the substance of the meniscus or if it extends to involve the joint surface. This is a critical differentiation because the latter represents meniscal tears that can be found and treated arthroscopically, whereas the former represents degeneration, intrasubstance tears or perhaps normal variants that are not amenable to arthroscopic intervention. The aim of this study was to investigate the occurrence of such borderline findings in relation to the posterior horn of the medial meniscus and to correlate the arthroscopic results.

MATERIALS AND METHODS

Sixty-four patients with suspected post-traumatic internal derangements of the knee who underwent MR imaging prior to arthroscopy were evaluated retrospectively. There were 48 men and 16 women. Their mean age was 28.2 years.

RESULTS

Tears of the posterior horn of the medial meniscus were diagnosed unequivocally (grade 3 signal) in 18 patients and equivocally (grade 2/3 signal) in 10 patients. Arthroscopic correlation revealed 16 tears (89%) in the unequivocal group and only 1 tear (10%) in the equivocal group.

CONCLUSION

A meniscal tear is unlikely when MR shows a focus of high signal intensity in the posterior horn of the medial meniscus that does not unequivocally extend to involve the inferior or superior joint surface. An appropriate trial of conservative treatment is recommended in such questionable cases. MR is a useful diagnostic tool-however, it should be used selectively, and in conjunction with history and clinical examination in evaluating internal derangements of the knee.

Magnetic resonance imaging of the knee in asymptomatic professional basketball players

PURPOSE

The purpose of this study was to evaluate the prevalence of articular cartilage lesions and meniscal tears on magnetic resonance imaging (MRI) scans in the knees of asymptomatic male professional basketball players.

TYPE OF STUDY

A retrospective review.

METHODS

Twenty players (40 knees) met the inclusion criteria of being signed by a National Basketball Association team and passing their preseason physical examination. All included athletes were assessed for the presence of articular cartilage lesions, meniscal pathology, and the presence of effusions.

RESULTS

The overall prevalence of articular cartilage lesions on MRI was 47.5% in our study group. There were trochlear groove articular lesions in 25%. The lateral femoral condyle was involved in 2.5% of all knees. The medial femoral condyle was affected in 10% of all knees. The lateral tibial plateau showed articular cartilage lesions in 5%. The patella had articular cartilage lesions in 35%. The overall prevalence of various grade meniscal lesions was 20% on MRI. Medial intra-meniscal signals accounted for 87.5% and 12.5% on the lateral side.

CONCLUSIONS

The results of our study show an equal to or higher prevalence of meniscal lesions in male professional basketball players than previously reported in the literature. We found a large number of patella-femoral articular cartilage lesions in our study population of male professional basketball players. These athletes perform at the highest demand level, which indicates that the presence of these lesions did not cause any symptoms.

LEVEL OF EVIDENCE

Level IV, case series.

Imaging the post-operative meniscus

Considerable developments have occurred in meniscal surgery, and consequently in the imaging of post-operative menisci, over the last 15 years. A drive to preserve meniscal physiologic function for as long as possible, in order to delay osteoarthrosis, has resulted in limited partial meniscectomies, meniscal repairs and meniscal transplants. Each of these techniques affects the imaging appearance of the meniscus, reducing the accuracy of conventional MRI in predicting recurrent tears. The specificity of conventional MRI can be improved by employing at least two T2-weighted sequences, but this still leaves a shortfall in sensitivity. In an attempt to increase the diagnostic accuracy of cross-sectional imaging, MR arthrography (MRA) and CT arthrography (CTA), have been applied to the post-operative meniscus. Sensitivities and specificities for these two techniques approach 90% in predicting recurrent meniscal tears. In the setting of clinical symptoms and gross meniscal deficiency, meniscal allografts are being transplanted with increasing frequency. In these transplants meniscal degeneration, fragmentation and separation are common findings, but the role of imaging in the management of these patients has not yet been well defined. This review explores the imaging techniques available for the evaluation of the post-operative meniscus, their strengths and weaknesses, and the reasons that they may find a place in a rational strategy for imaging of the symptomatic post-operative knee.

Clinical diagnostic accuracy and magnetic resonance imaging of patients referred by physical therapists, orthopaedic surgeons, and nonorthopaedic providers

STUDY DESIGN

Nonexperimental, retrospective design.

OBJECTIVES

This study was designed to compare clinical diagnostic accuracy (CDA) between physical therapists (PTs), orthopaedic surgeons (OSs), and nonorthopaedic providers (NOPs) at Keller Army Community Hospital on patients with musculoskeletal injuries (MSI) referred for magnetic resonance imaging (MRI).

BACKGROUND

US Army PTs are frequently the first credentialed providers privileged to examine and diagnose patients with musculoskeletal injuries. Physical therapists assigned at Keller Army Community Hospital have also been credentialed with privileges to order MRI studies for several years.

METHODS AND MEASURES

To reduce provider bias, a retrospective analysis was performed on 560 patients referred for MRI over an 18-month period. An electronic review of each patient's radiological profile was performed to assess agreement between clinical diagnosis and MRI findings. Data analyses were performed through descriptive statistics and contingency tables.

RESULTS

Analysis on agreement between clinical diagnosis and MRI findings produced a CDA of 74.5% (108/145) for PTs, 80.8% (139/172) for OSs, and 35.4% (86/243) for NOPs. There was a significant difference in CDA between PTs and NOPs (P<.001), and between OSs and NOPs (P<.001). There was no difference in CDA between PTs and OSs (P>.05).

CONCLUSIONS

Clinical diagnostic accuracy by PTs and OSs on patients with musculoskeletal injuries was significantly greater than for NOPs, with no difference noted between PTs and OSs.

Imaging evaluation of meniscal injury of the knee joint: a comparative MR imaging and arthroscopic study

To evaluate the efficacy of MR imaging in the diagnosis and classification of meniscal tear of the knee joint, we retrospectively characterized the MR features of 78 meniscal tears in 148 patients according to the Mesgarzadeh's criteria. The results showed that the sensitivity and specificity for meniscal tears were 92% and 87%, respectively. Type VI meniscal tear was the most common type, especially in displaced meniscal tear. MR is a reliable diagnostic tool for meniscal tears and associated cruciate ligament injury.

The “Floating” Meniscus: MRI in Knee Trauma and Implications for Surgery

OBJECTIVE

We describe 21 cases involving meniscal injury in which the meniscus appears free-floating on MRI of the knee. In these cases, the meniscus is completely surrounded by fluid. Correlation with surgical reports shows that the "floating" meniscus corresponds to a meniscal avulsion or detachment from the tibial plateau with an associated disruption of the meniscotibial coronary ligaments, which attach the meniscus to the tibia, allowing fluid to encompass the meniscus. A floating meniscus on MRI may represent a new specific finding for an uncommon form of meniscal injury known as meniscal avulsion.

CONCLUSION

The presence of a floating meniscus on MRI is a result of significant trauma to the knee leading to meniscal avulsion and is often associated with significant ligamentous injury. Alerting the surgeon to the presence of a meniscal avulsion facilitates appropriate surgical planning with meniscal reattachment to the tibial plateau.

Detection of meniscal tears and marrow lesions using coronal MRI

OBJECTIVE

The usefulness of coronal images in addition to sagittal images for detection of additional meniscal injuries or bone lesions has been questioned. Some authors believe meniscal tears are rarely seen only in the coronal plane. We performed a retrospective review of coronal and sagittal MR images of the knee to determine whether coronal imaging resulted in the detection of any additional meniscal tears or bone lesions when compared with sagittal MRI of the knee alone.

MATERIALS AND METHODS

Two musculoskeletal radiologists retrospectively reviewed 200 consecutive sets of MR images of the knee by consensus. Both observers recorded their retrospective findings on sagittal proton density images, sagittal and coronal T2-weighted images, and coronal T1-weighted images. Findings recorded were those of meniscal tears, bone marrow abnormalities, and bone lesions.

RESULTS

On these 200 consecutive sets of MR images of the knee, 114 meniscal tears were shown. Ninety-three meniscal tears were shown on sagittal proton density images only. One hundred fourteen meniscal tears were seen on sagittal proton density and coronal T1- and T2-weighted images. Use of coronal images resulted in the confident detection of 21 additional meniscal tears not well seen on sagittal proton density images alone. Twelve of the 21 additional meniscal tears were seen on coronal T1- and T2-weighted images. Nine of the 21 additional meniscal tears were seen only on coronal T1-weighted images. Most of these additional meniscal tears were in the body of the meniscus. These 21 additional meniscal tears were confirmed arthroscopically. Eight marrow lesions were well characterized only on coronal T1-weighted images. Five were osteochondral lesions, one was an intraosseous hemangioma, and two were microfractures.

CONCLUSION

Coronal MR images of the knee allowed better detection and characterization of some meniscal tears than sagittal images alone. Radial meniscal tears, bucket-handle tears, and horizontal tears in the body of the meniscus may be difficult to characterize in the sagittal plane alone. Use of coronal T1-weighted images, rather than coronal T2-weighted or sagittal proton density images alone, allows accurate characterization of some additional marrow lesions. The addition of a T1-weighted sequence in the coronal plane adds only 1 min 30 sec to the scanning time.

Meniscal Tears:Role of Axial MRI Alone and in Combination with Other Imaging Planes

OBJECTIVE

The purpose of this study was to determine the reliability of standard axial MR images alone in the diagnosis of meniscal tears of the knee and in combination with other imaging planes.

MATERIALS AND METHODS

Sixty-two patients (55 men, seven women; age range, 23-68 years) with a prior MRI examination who underwent arthroscopic surgery of the knee during a 1-year period were included in the study group. Images were independently reviewed for identification of meniscal tears by two musculoskeletal radiologists blinded to arthroscopic findings. Sequences for meniscal evaluation included axial fat-saturated fast spin-echo proton density, coronal fat-saturated fast spin-echo proton density, and sagittal fast spin-echo proton density with 4- to 5-mm slice thicknesses. Imaging groups for evaluation were axial, coronal, sagittal, axial and sagittal, axial and coronal, and coronal and sagittal. Observers reported a confidence level for the presence or absence of meniscal tear in all imaging groups based on a 5-point scale. Statistical analysis considered medial and lateral menisci separately.

RESULTS

Forty patients had medial meniscal tears, and 16 had lateral meniscal tears at arthroscopy. For medial and lateral meniscal tears, the accuracy (79% and 71%, respectively) of imaging in the axial plane was comparable to other imaging groups but the mean confidence levels (2.82 and 3.00, respectively) were low. In one patient, the axial plane alone correctly showed that no tear was present. No statistically significant difference was observed between imaging plane groups of both menisci in the diagnosis of meniscal tears (p > 0.05). The axial plane increased the accuracy of sagittal and coronal planes of lateral meniscus when combined.

CONCLUSION

In standard knee MRI examinations, the axial imaging plane may be valuable for the detection and characterization of meniscal tears.

Clinical and arthroscopic features of meniscal tears and a search for the role of infection in histologically confirmed meniscal mucoid degeneration

Mucoid degeneration (MD) of the meniscus has received little attention. The pathology deserves special interest as it may lead to loss of the meniscus even in very young individuals. The cause of MD and the clinical features of meniscal tears due to that pathology have not been understood. This study analyzed the age profile and the role of trauma in patients with torn menisci with MD, examined meniscal tear patterns and clinical features, and investigated the role of bacterial infection in causing MD. Meniscal samples obtained from 27 consecutive patients during arthroscopic resection of torn menisci considered to be due to MD (typical yellow color) underwent pathological investigation. The samples were scored according to the light microscopic criteria of Copenhaver; 24 menisci (23 patients) with stage 2-3 MD comprised the study group. Magnetic resonance imaging obtained in 11 patients typically revealed increased intrasubstance signal intensity that extended to at least one of the meniscal surfaces. Pieces of resected meniscal tissue were also subject to PCR investigation to search for presence of bacteria. Of the 24 knees 21 (87%) had no history of trauma. Mean Tegner activity level was 4 (1 and 7). Mean duration of symptoms was 11.6 months (1-36). Pain was the most frequent symptom ( n=22). Joint line tenderness and McMurray's test (pain and/or clicking) were present in 22 and 16 knees, respectively. Medial meniscus was affected in 16 and lateral meniscus in 8. Meniscal cyst and incomplete discoid meniscus was present in 5 and 2 of the lateral menisci. All of the torn menisci were degenerated and yellow in color. The most common tear patterns were radial and/or flap, and longitudinal-horizontal tears. PCR study revealed no bacteria. Mucoid degeneration of the meniscus does not seem to be related to the aging process. Clinical findings of torn such menisci are insidious compared to traumatic tears. Lack of history of trauma may delay the diagnosis. Bacterial infection has no role in the cause.

CT arthrography and virtual arthroscopy in the diagnosis of the anterior cruciate ligament and meniscal abnormalities of the knee joint

Objective

To determine the diagnostic accuracy of CT arthrography and virtual arthroscopy in the diagnosis of anterior cruciate ligament and meniscus pathology.

Materials and Methods

Thirty-eight consecutive patients who underwent CT arthrography and arthroscopy of the knee were included in this study. The ages of the patients ranged from 19 to 52 years and all of the patients were male. Sagittal, coronal, transverse and oblique coronal multiplanar reconstruction images were reformatted from CT arthrography. Virtual arthroscopy was performed from 6 standard views using a volume rendering technique. Three radiologists analyzed the MPR images and two orthopedic surgeons analyzed the virtual arthroscopic images.

Results

The sensitivity and specificity of CT arthrography for the diagnosis of anterior cruciate ligament abnormalities were 87.5%-100% and 93.3-96.7%, respectively, and those for meniscus abnormalities were 91.7%-100% and 98.1%, respectively. The sensitivity and specificity of virtual arthroscopy for the diagnosis of anterior cruciate ligament abnormalities were 87.5% and 83.3-90%, respectively, and those for meniscus abnormalities were 83.3%-87.5% and 96.1-98.1%, respectively.

Conclusion

CT arthrography and virtual arthroscopy showed good diagnostic accuracy for anterior cruciate ligament and meniscal abnormalities.

Magnetic resonance imaging for investigation of the knee joint: A clinical and economic evaluation

Objectives:The aim of the study reported here was to investigate whether the use of magnetic resonance imaging (MRI) impacts on the clinical management of patients presenting with chronic knee problems, reduces costs, and improves patient outcome.

Methods:A single-center randomized controlled trial was conducted. Patients attending with knee problems in whom surgery was being considered were randomized either to investigation using an MRI scan or to investigation using arthroscopy. The study investigated benefits in terms of avoidance of surgery and patient health-related quality of life (using SF-36 and EQ-5D). Costs were assessed from the perspectives of the National Health Service and patients. All analyses were by intention to treat.

Results:The trial recruited 118 patients. No statistically significant differences were found between groups in terms of health outcome. However, the use of MRI was associated with a positive diagnostic/therapeutic impact: a significantly smaller proportion of patients in the MRI group underwent surgery (MRI=0.41, No-MRI=0.71;pvalue=.001). There was a similar mean overall cost for both groups.

Conclusions:The use of MRI in patients with chronic knee problems, in whom surgery was being considered, did not increase costs overall, was not associated with worse outcomes, and avoided surgery in a significant proportion of patients.

Evaluation of recurring meniscal tears with gadolinium-enhanced magnetic resonance imaging: a randomized, prospective study

BACKGROUND

Magnetic resonance imaging has been shown to be of questionable accuracy in detecting recurrent meniscal tears after previous resection or repair.

PURPOSE

To compare the accuracy of nonenhanced magnetic resonance imaging with that of intraarticular contrast-enhanced direct magnetic resonance arthrography and intravenous contrast-enhanced indirect magnetic resonance arthrography for detection of recurrent meniscal tears.

STUDY DESIGN

Prospective cohort study.

METHODS

Forty-one patients who had previous meniscal tears treated by resection or repair but who were experiencing recurrent knee symptoms were prospectively randomized into one of three groups: conventional magnetic resonance imaging, indirect arthrography, and direct arthrography. The interpretations of two musculoskeletal radiologists were compared with the findings of an arthroscopic procedure performed 2 to 14 weeks later.

RESULTS

Conventional imaging had a sensitivity of 57.9%, specificity of 80%, and overall accuracy of 62.5%. Intravenous contrast improved the sensitivity to 90.9%, specificity to 100%, and overall accuracy to 93.8%; intraarticular contrast had a sensitivity of 91.7%, specificity of 100%, and an overall accuracy of 92.9%.

CONCLUSIONS

We demonstrated an increased accuracy of intravenous or intraarticular contrast-enhanced magnetic resonance arthrography in detecting recurrent meniscal tears. Both contrast routes demonstrated similar accuracy, a finding not previously reported.

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 menisci and cruciate ligaments: a systematic review

PURPOSE

To systematically review and synthesize published data on the diagnostic performance of magnetic resonance (MR) imaging of the menisci and cruciate ligaments and to assess the effect of study design characteristics and magnetic field strength on diagnostic performance.

MATERIALS AND METHODS

Articles published between 1991 and 2000 were included if at least 30 patients were studied, arthroscopy was the reference standard, the magnetic field strength was reported, positivity criteria were defined, and the absolute numbers of true-positive, false-negative, true-negative, and false-positive results were available or derivable. Pooled weighted and summary receiver operating characteristic (ROC) analyses were performed for tears of both menisci and both cruciate ligaments separately and for the four lesions combined, by using random effects models. Differences were assessed according to lesion type.

RESULTS

Twenty-nine of 120 retrieved articles were included. Pooled weighted sensitivity was higher for medial meniscal tears than that for lateral meniscal tears. However, pooled weighted specificity for the medial meniscus was lower than that for the lateral meniscus. In summary ROC analyses performed per lesion, various study design characteristics were found to influence diagnostic performance. Higher magnetic field strength significantly improved discriminatory power only for anterior cruciate ligament tears. When all lesions were combined in one overall summary ROC analysis, magnetic field strength was a significant but modest predictor of diagnostic performance.

CONCLUSION

Diagnostic performance of MR imaging of the knee is different according to lesion type and is influenced by various study design characteristics. Higher magnetic field strength modestly improves diagnostic performance, but a significant effect was demonstrated only for anterior cruciate ligament tears.

Meniscal tear configurations: categorization with MR imaging

OBJECTIVE

The purpose of this study was to evaluate the accuracy of MR imaging for categorizing the configuration of meniscal tears of the knee.

MATERIALS AND METHODS

Fast spin-echo MR images obtained at 1.5 T from 110 patients who had meniscal tears identified at arthroscopy were retrospectively and independently classified by two reviewers into five configurations: horizontal, longitudinal, radial, oblique, and complex. MR imaging categorization was compared with arthroscopic results as the standard of reference. Data were also analyzed with longitudinal and oblique tears combined because these usually are reparable, and with horizontal, radial, and complex tears combined because these usually are not reparable. Interobserver and intraobserver agreements were calculated using kappa coefficients.

RESULTS

At arthroscopy, meniscal tears were categorized as horizontal (n = 44), longitudinal (n = 34), complex (n = 22), radial (n = 11), and oblique (n = 5). Sensitivity, specificity, and accuracy of each reviewer for the reparable tears were 82%, 92%, and 89%; and 59%, 97%, and 84%, respectively. Interobserver agreements were fair between reviewer 1 and the first and second interpretations of reviewer 2 (kappa = 0.25, p < 0.005; and kappa = 0.21, p < 0.05, respectively). Intraobserver agreement was substantial (kappa = 0.71, p < 0.001).

CONCLUSION

MR imaging was accurate for predicting reparable meniscal tears and was sensitive for the determination of nonreparable tears.

The clinical importance of meniscal tears demonstrated by magnetic resonance imaging in osteoarthritis of the knee

BACKGROUND

Meniscal tears are frequently found during magnetic resonance imaging of osteoarthritic knees. However, the prevalence and clinical relevance of these tears have not been determined. This study was designed to investigate the relationship between meniscal tears and osteoarthritis and between such tears and pain in patients with osteoarthritis.

METHODS

Magnetic resonance imaging and plain radiography of the knee were performed in a group of 154 patients with clinical symptoms of knee osteoarthritis and a group of forty-nine age-matched asymptomatic controls. Pain scores (according to a 100-mm visual analog scale) and functional scores (according to the Western Ontario and McMaster University Osteoarthritis Index [WOMAC]) were determined for ninety-one of the patients with symptomatic osteoarthritis. Meniscal tears were defined as tears extending to an articular surface as seen on magnetic resonance imaging.

RESULTS

A medial or lateral meniscal tear was a very common finding in the asymptomatic subjects (prevalence, 76%) but was more common in the patients with symptomatic osteoarthritis (91%) (p < 0.005). In the group with symptomatic osteoarthritis, a higher Kellgren-Lawrence radiographic grade was correlated with a higher frequency of meniscal tears (r = 0.26, p < 0.001), and men had a higher prevalence of meniscal tears than did women (p < 0.01). However, there was no significant difference with regard to the pain or WOMAC score between the patients with and those without a medial or lateral meniscal tear in the osteoarthritic group (p = 0.8 to 0.9 for all comparisons). The power of the study was 80% to detect a difference in the WOMAC scores of 15 points and a difference in the scores on the visual analog scale of 16 mm.

CONCLUSIONS

Meniscal tears are highly prevalent in both asymptomatic and clinically osteoarthritic knees of older individuals. However, osteoarthritic knees with a meniscal tear are not more painful than those without a tear, and the meniscal tears do not affect functional status. These data do not support the routine use of magnetic resonance imaging for the evaluation and management of meniscal tears in patients with osteoarthritis of the knee.

LEVEL OF EVIDENCE

Diagnostic study, Level I-1 (testing of previously developed diagnostic criteria in series of consecutive patients [with universally applied reference "gold" standard]). See p. 2 for complete description of levels of evidence.

Prevalence of abnormal findings in magnetic resonance images of asymptomatic knees

One hundred fifteen asymptomatic Japanese volunteers aged from 13 to 76 years were examined by magnetic resonance imaging (MRI) to evaluate age-related meniscal degeneration and to determine the prevalence of discoid menisci. Each meniscus was graded in the anterior and posterior portions according to intrameniscal MRI signals. Discoid meniscus was diagnosed if a bow-tie configuration was noted on three or more contiguous sagittal sections. Meniscal abnormalities on MRI became more prevalent with age in both men and women. The posterior horn of the medial meniscus showed a significantly higher prevalence of degeneration than other parts of the meniscus. Discoid menisci were noted in 15 subjects (13% prevalence), always representing the lateral meniscus. Subchondral changes were observed in 13 subjects more than 40 years old, mostly women, and were located in the medial compartment. These abnormalities were not correlated with severity of degeneration in the posterior portion of the medial meniscus. This study demonstrates considerable prevalence of meniscal abnormalities in asymptomatic Japanese subjects.

Grade 2C signal in the meniscus [correction of mensicus] on MR imaging of the knee

OBJECTIVE

The objective of our study was to evaluate the clinical significance of grade 2C meniscal [corrected] signal (an extensive triangular or wedge-shaped signal that does not reach the surface on more than one image) on MR imaging of the knee.

MATERIALS AND METHODS

Review of 1106 MR imaging reports over 2 years revealed 88 patients with menisci described as containing triangular, wedge-shaped, extensive, or grade 2C signal. Image review by consensus of two radiologists found 34 menisci in 29 patients that fit criteria for grade 2C signal. Seven menisci containing grade 2C signal were evaluated with arthroscopy. An additional three patients with grade 2C meniscal signal with arthroscopic correlation were identified from 4 previous years.

RESULTS

Prevalence of grade 2C signal was 1.5% (34/2212 menisci). Seven (21%) of these 34 menisci had subsequent arthroscopy and three of these had meniscal tears. Including the three additional menisci with grade 2C signal from 4 previous years, five (50%) of 10 menisci with grade 2C signal were torn at arthroscopy. No difference was noted between torn and intact menisci in the number of images with grade 2C signal. In patients with tears, the range was three to 10 images (mean, 6.6 images) compared with a range of two to 10 images (mean, 6.6 images) in patients without tears. The maximal percentage of area of abnormal signal in patients with tears ranged from 70% to 90% (mean, 80%) compared with a range of 60-90% (mean, 82%) in patients without tears. The patient age range was 23-64 years (mean, 47 years) in patients with tears and 16-67 years (mean, 47 years) in patients without tears.

CONCLUSION

Grade 2C meniscal signal has a low incidence. Although half of patients with symptoms meriting arthroscopy have tears, most patients with grade 2C signal are not treated with arthroscopy.

MR imaging of the knee: findings in asymptomatic collegiate basketball players

OBJECTIVE

The purpose of our study was to evaluate the knees of asymptomatic high-level collegiate basketball players before the beginning of the basketball season to gain an understanding of nonclinical findings in this patient population.

SUBJECTS AND METHODS

Bilateral knee MR imaging examinations of 17 varsity basketball players (12 men and five women) were performed before basketball season began. All of the subjects were imaged on a 1.5-T magnet. The MR imaging studies were reviewed by two musculoskeletal radiologists. Structures analyzed were the menisci, ligaments, cartilage, plicae, and bone marrow. The presence of a joint effusion was also noted.

RESULTS

Fourteen (41%) of the 34 knees had bone marrow edema, eight (24%) showed signal in the patellar tendon, and 14 (41%) had abnormal cartilage signal or a focal abnormality. Twelve (35%) of the 34 knees showed a joint effusion. Two knees (6%) showed abnormal signal along the infrapatellar plica. Four knees (12%) were noted to have a discoid meniscus.

CONCLUSION

An MR examination of the knees of high-level collegiate basketball players may show changes unique to this population. The changes seen on MR imaging in these athletes may be asymptomatic abnormalities. For instance, changes suggestive of patellar tendinopathy were identified in these asymptomatic subjects.

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.

Lack of posteromedial tibiofemoral congruence at full flexion as a causative factor in isolated medial meniscal tears

The aim of the current study was to investigate posteromedial tibiofemoral congruence at full flexion of the knee in control knee joints and those affected by an isolated medial meniscal tear, to examine whether lack of such congruence was a causative factor in isolated medial meniscal tears. In this study, 1677 knee joints in 875 subjects were evaluated. The joints were classified as a control group (1345 joints), an isolated medial meniscal tear group (224 joints), and a contralateral isolated medial meniscal tear group (108 joints). Posteromedial tibiofemoral congruence was examined on a lateral radiograph of the knee joint at full flexion. The tangent touching the anterior and posterior parts of the articular surface of the medial tibial condyle was assumed to be the X-axis. To evaluate posteromedial tibiofemoral congruence, we measured the angle formed by the tangent that maximized the gradient of the tangent on the articular surface of the medial femoral condyle, and the tangent that maximized the gradient of the tangent on the articular surface of the medial tibial condyle. The mean angle differed significantly between the control and the isolated medial meniscal tear groups, regardless of sex. Isolated medial meniscal tears were found to be strongly related to an abnormally decreased angle, and, therefore, incongruence of the posteromedial tibiofemoral articulation at full flexion was considered to be one of the causes of isolated medial meniscal tears.

Anterior cruciate ligament tears and associated meniscal lesions: assessment at dual-detector spiral CT arthrography

PURPOSE

To assess dual-detector spiral computed tomographic (CT) arthrography of the knee in the evaluation of anterior cruciate ligament (ACL) tears and associated meniscal lesions.

MATERIALS AND METHODS

ACL and meniscal abnormalities in 125 consecutive patients who underwent dual-detector spiral CT arthrography of the knee were evaluated on the basis of both initial interpretations and retrospective review of CT images and were compared with arthroscopic findings. The sensitivity and specificity of CT arthrography for the detection of ACL tears and meniscal lesions in knees with abnormal ACLs were determined.

RESULTS

The sensitivities and specificities for the detection of ACL tears were 90% and 96%, respectively, at initial interpretation and 95% and 99%, respectively, at retrospective interpretation. The sensitivities and specificities for the detection of meniscal tears in knees with abnormal ACLs were 92% and 88%, respectively, at initial interpretation and 96% and 94%, respectively, at retrospective interpretation.

CONCLUSION

Dual-detector spiral CT arthrography of the knee is an accurate method for detecting ACL tears and associated meniscal lesions.

Magnetic resonance imaging of the multiple-ligament injured knee

OBJECTIVE

To evaluate magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in detecting soft tissue, neurovascular, and bony injury after multiple ligament knee injury, including knee dislocation.

MATERIALS AND METHODS

A retrospective search was performed for patients presenting with reported knee dislocation from May 1993 through May 2000 who underwent both MRI and surgical reconstruction. Twenty-one patients met these criteria (15 men and six women; age range 14 to 75 years; mean 32.6 years). Magnetic resonance diagnoses of soft tissue and bony injury were compared with the patients' operative findings. MRA of the popliteal vessels was performed in seventeen of our twenty-one patients, and the results of these studies are described.

RESULTS

Multiple ligamentous, tendinous, meniscal, chondral, osseous, and neural injuries were seen. There was excellent correlation (kappa > 0.8) between the magnetic resonance and operative findings with regard to the size and location of tears. Regarding meniscal tears, the type (e.g., bucket, radial split, meniscocapsular separation) and location correlated well with surgery. All ten nerve injuries noted on magnetic resonance were confirmed at surgery. Six of our patients had both conventional angiograms and MRAs with 100 percent agreement between the studies. In one patient an intimal flap in the popliteal artery was seen on MRA and confirmed on conventional angiographic images.

CONCLUSION

MRI is an accurate method of assessing soft tissue, osseous, and neural damage after knee dislocation. Our early experience with popliteal fossa MRA is encouraging with complete agreement between the MRA and conventional angiography in patients who had both studies.

Magnetic resonance imaging of the knee

Magnetic resonance imaging (MRI) has revolutionised diagnostic imaging of the knee. It has evolved significantly since Kean described healthy and pathologic knee anatomy in 1983. This innovative technology allows superior soft-tissue detail with multiplanar imaging capability that provides accurate evaluation of intra- and extra-articular structures of the knee not demonstrated with other imaging modalities. The development and advancements in MRI and the introduction of high-resolution coils have provided a noninvasive, nonoperator dependent, cost effective means to diagnose knee pathology. MRI is well tolerated by patients, widely accepted by evaluating physicians, and assists in distinguishing pathologic knee conditions that may have similar clinical signs and symptoms (i.e. meniscal tears, osteochondral lesions). This paper presents an overview of MRI of the knee and focuses on the MRI findings in a number of common pathologic conditions.

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.

Comparison of knee magnetic resonance imaging findings in patients referred by orthopaedic surgeons versus nonorthopaedic practitioners

PURPOSE

To compare the percentages of normal magnetic resonance imaging (MRI) examination results and clinically significant knee abnormalities in patients referred for MRI of the knee by orthopaedic surgery residents and staff with those of patients referred by nonorthopaedic practitioners.

TYPE OF STUDY

Retrospective review of MRI findings.

METHODS

MRI reports of 754 patients (454 men and 300 women) were retrospectively reviewed; 373 patients were referred from the Department of Orthopaedic Surgery and 381 patients were referred from nonorthopaedic practitioners. The number of normal examination results, meniscal and ligament tears, chondral abnormalities, and Baker's cysts was tabulated and analyzed using a X-square injury analysis.

RESULTS

The rate of normal results for nonorthopaedic practitioners was 33.9% (129 of 381) compared with 15.3% (57 of 373) for orthopaedic surgeons (P <.001). Nonorthopaedic surgeons referred 69.4% (129 of 186) of the patients who had normal examination results. The positive finding for a lateral meniscus tear was 29.2% (109 of 373) for orthopaedic surgeons compared with 19.1% (73 of 381) for nonorthopaedic practitioners, which was statistically significant (P =.002) in regard to the distribution of injuries. No difference was found in other abnormalities assessed.

CONCLUSIONS

Patients referred by nonorthopaedic practitioners had significantly more normal knee MRI examination results than did those referred by orthopaedic surgeons.

Clinical value of magnetic resonance imaging of the knee

BACKGROUND

Magnetic resonance (MR) imaging is an accurate imaging modality of the knee. The role of MR in clinical practice has not been precisely defined, largely due to the relative expense of the technique.

METHODS

For each new patient with a knee problem who was referred for MR, a provisional diagnosis was made together with a level of certainty regarding the diagnosis. The waiting time for the scan was recorded. To assess clinical usefulness the MR diagnosis was compared with the provisional diagnosis and classified according to the following descending order of value: unexpected negative (no intra-articular pathology), confirmatory negative, unexpected positive or confirmatory positive. To assess accuracy of the MR diagnosis, the operative diagnosis was compared to the MR diagnosis in those patients who underwent arthroscopy.

RESULTS

Fifty-two per cent of scans were assessed as being very useful and a further 20% were assessed as being moderately useful. Magnetic resonance had a 95% accuracy for medial meniscal tears, 91% accuracy for lateral meniscal tears, and 98% accuracy for anterior cruciate ligament tears, similar to previously reported studies. The diagnostic arthroscopy rate in the patients who underwent MR scanning was similar to that in patients for whom the surgeon was more confident about the diagnosis and who therefore did not undergo MR scanning. The diagnostic arthroscopy rate could have been reduced if surgery had not been performed in 14 patients who had a negative MR scan.

CONCLUSIONS

There is a role for selective use of MR in the assessment of knee conditions. In particular, MR can be used to reduce the diagnostic arthroscopy rate.

MR imaging of meniscal cysts: incidence, location, and clinical significance

OBJECTIVE

The purpose of this study was to determine the incidence of medial versus lateral meniscal cysts as seen on MR imaging.

MATERIALS AND METHODS

A total of 2572 knee MR imaging reports were retrospectively reviewed for the presence of meniscal tears and cysts. Two musculoskeletal radiologists reviewed all images with reported cysts. The type and location of meniscal tear and the presence and location of meniscal cysts were recorded.

RESULTS

A total of 1402 meniscal tears were reported in 2572 MR examinations (922 [66%] of 1402 in the medial compartment; 480 [34%] of 1402 in the lateral compartment). Meniscal cysts were present in 109 (4%) of 2572 knees. Of the 109 cysts, 72 (66%) were in the medial compartment, and 37 (34%) were in the lateral compartment. Meniscal cysts were found in association with 72 (7.8%) of the 922 medial meniscal tears and 37 (7.7%) of the 480 lateral meniscal tears. Meniscal cysts showed direct contact with an adjacent meniscal tear in 107 (98%) of 109 cases, with the tear showing a horizontal component in 96 (90%) of 107 cases.

CONCLUSION

Meniscal cysts occur almost twice as often in the medial compartment as in the lateral compartment. Medial and lateral tears occur with the same frequency. These findings, when viewed in the context of the historical literature on meniscal cysts, suggest that MR imaging detects a greater number of medial meniscal cysts than physical examination or arthroscopy, and that MR imaging can have an important impact on surgical treatment of patients.