MR imaging of meniscal tears with discoid lateral meniscus
Introduction
A discoid lateral meniscus (DLM) of the knee described as a congenital and morphologically enlarged meniscus is not an uncommon anomaly 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. Although a discoid lateral meniscus itself may cause `snapping knee syndrome' or gonalgia 5, 6, 7, clinical symptoms should appear mainly when a DLM is injured. So it is of great importance to know the presence of meniscal tears with DLM in presurgical planning. Lately, MR has become the first choice of modality to evaluate the knee structure 1, 8, 9, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, so we tried to study MR appearances of torn DLM.
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Materials and methods
From January 1990 to July 1993, we had examined 1140 knees (969 patients) with MRI. In these knees, surgically proved 57 DLMs (40 patients) were consecutively selected and studied. All associated meniscal tears were confirmed by surgery in our study. Of them, 17 patients underwent arthroscopical surgery in both knees. However, the other 23 patients (all had DLMs on both knees) underwent surgery in one knee because the other knee was not symptomatic. They were 18 men and 22 women, ranging in age
Results
According to Watanabe's classification [11], we arthroscopically classified 57 DLM; 32 as complete type and 25 as incomplete type. Of 32 complete DLMs, meniscal tears were observed in 25 DLMs, whereas only one opposite medial meniscus was injured. As to 25 incomplete DLM, 13 DLMs and six opposite medial menisci were injured. The remaining 19 DLMs (seven complete and 12 incomplete DLMs) had no tears.
Of 38 DLMs with meniscal tears, nine menisci (seven complete and two incomplete DLMs) had
Discussion
Meniscal tears are main clinical pathologic lesions of the menisci 5, 8, 11, 15, 20, 24, 26, 27, 28and DLMs have been said to be more commonly injured than the normally shaped lateral menisci [26]. This is supported by our results that DLM had the much higher incidence of meniscal tears than the opposed medial menisci by 38:6 (Table 1). Generally, a medial meniscus is thought to be at greater risk for tears than a lateral meniscus because the former has greater radius of curvature and tight
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Discoid lateral meniscus: Current concepts
2021, Journal of ISAKOSDiscoid Meniscus in the Pediatric Population:: Emphasis on MR Imaging Signs of Instability
2019, Magnetic Resonance Imaging Clinics of North AmericaCitation Excerpt :Different from the degenerative type of meniscal tear seen in adults that tend to affect the medial meniscus, tears involving the lateral meniscus are more common in the pediatric population due to their association with sports-related injuries and the higher incidence of DM laterally.7,16,47,48 It is likely that the predisposition of DM to tears is multifactorial in part due to the abnormal morphology and structure as well as the degree of shear forces placed on the unfit substance of DM to resist mechanical stress.9,10,12,33,41,42,49,50 All types of meniscal tears, including complex tears, have been described affecting DM, the complete type being more frequently affected than the incomplete type DM (Table 2).9,33,42,49,51
Meniscal morphologic changes on magnetic resonance imaging are associated with symptomatic discoid lateral meniscal tear in children
2012, Arthroscopy - Journal of Arthroscopic and Related SurgeryVerification Bias. An Under-Recognized Source of Error in Assessing the Efficacy of MRI of the Meniscii.
2011, Academic RadiologyCitation Excerpt :A total of 314 studies were retrieved from the PubMed keyword search. Of these, 39 of 314 specifically dealt with meniscal tears (15–53). Surgery or arthroscopy was the reference standard used by most of these studies, although clinical follow-up was used as a secondary standard by some investigators.
Bilateral discoid lateral meniscus in knees: Evaluation of the contralateral knee in patients with symptomatic discoid lateral meniscus
2010, Arthroscopy - Journal of Arthroscopic and Related SurgeryCitation Excerpt :If the characteristic findings of DLM are seen on the plain radiographs, an MRI study should be considered. MRI is now widely accepted as an accurate, noninvasive imaging modality for detecting meniscal abnormalities and for assessing a DLM.26-28 The technique can be used to confirm the clinical diagnosis of a DLM and to detect associated abnormalities such as tears or concomitant chondral lesions.
MR Imaging of Meniscal and Cartilage Injuries of the Knee
2009, Magnetic Resonance Imaging Clinics of North AmericaCitation Excerpt :Coronal MR imaging demonstrates extension of the apex of a discoid meniscus toward or into the intercondylar notch, with a coronal distance of 13 mm from the capsular margin to the free edge being highly suggestive of a discoid meniscus.2 Discoid menisci are prone to meniscal tears and degeneration because of their abnormal structure.42 The frequency of all types of meniscal tears is higher in discoid menisci, with no increase in frequency of tears of the adjacent normal meniscus.43