Diagnosis of meniscal tears on MRI improves when these guidelines are followed to optimize signal-to-noise ratio: high-field-strength magnets are preferable (1.5 T and stronger); a high-resolution surface coil should be used; the field of view should only encompass the necessary structures and routinely be 16 cm or less; image slices should not be too thick (34 mm); and the matrix size should be at least 256192 or higher [, A normal meniscus is low signal on all sequences. A 2003 systematic review of the literature, in which 29 publications met strict inclusion criteria, demonstrated pooled weighted sensitivity and specificity of 93.3 % and 88.4 % for the medial meniscus and 79.3 % and 95.7 % for the lateral meniscus, respectively [, Most meniscal tears are visible and best seen on sagittal images. It is possible that there could have been some tears missed at arthroscopy that were on the undersurface of the anterior horn, an area which is extremely difficultif not impossibleto visualize. treatment for stable complete or incomplete types of discoid lateral Clark CR, Ogden JA. the example shown (Figures 1 and 2), the entire medial meniscus is Pathology - a tear that has developed gradually in the meniscus. Absence of the meniscus results in a 200 to 300% increase in contact stresses on the articular surfaces.8The meniscus has a heterogeneous cellular composition with regional and zonal variation, with high proteoglycan content at the thin free edge where compressive forces predominate and low proteoglycan content at the thicker peripheral region where circumferential tensile loads predominate. With age, increased connective tissue stiffness of the meniscus develops secondary to elastin degradation and collagen rigidification.2. Disadvantages include patient discomfort, increased cost, physician time needed for the procedure and radiation exposure during fluoroscopy. This mesenchymal Br Med Bull. The purpose of our study was to determine if cysts of the ACL are the origin of cysts adjacent to the AHLM. immediatly lateral to the anterior horn of lateral meniscus and posterior to the tubercle of anteriro horn of medial meniscus . As DLM is a congenital anomaly, the ultrastructural features and morphology differ from those of the normal meniscus, potentially leading to meniscal tears. The posterior horn is always larger than the anterior horn. Kocher MS, Klingele K, Rassman SO. At least one meniscofemoral ligament is present in 7093 % Of knees MRI features are consistent with torn lateral meniscus with flipped anterior horn superomedial and posterior, resting superior to the posterior horn. Advantages include a less invasive method of introducing intraarticular contrast, the ability to identify areas of hyperemic synovitis or periarticular inflammation based on enhancement and administration can be performed by the technologist. This emphasizes the importance of meniscal repair over meniscectomy when possible and the need for meniscal preservation when a partial meniscectomy is necessary. Normal menisci. Again, this emphasizes the importance of accurate history, prior imaging and operative reports. Medial meniscus bucket handle tears can result in a double PCL sign. The meniscus can separate from the joint capsule or tear through the allograft. Kim EY, Choi SH, Ahn JH, Kwon JW. Type joint, and they also protect the hyaline cartilage. in 19916. Findings indicate an intact meniscus following partial meniscectomy with normal intrameniscal signal. History of longitudinal medial meniscus tear managed by meniscal repair (arrows). The most widely used diagnostic modalities to assess the ligament injuries are arthroscopy and Magnetic Resonance Imaging (MRI). Their conclusion that one should not perform surgery unless clinical correlation exists with effusions, mechanical catching or locking, or the failure to respond to nonoperative measures I believe is a good recommendation that we can all follow. This case features the following signs of meniscal tear: Case courtesy, Prof. Dr. Khaled Matrawy, Professor of radiology, Alexandria university, Egypt. They often tend to be radial tears extending into the meniscal root. Of the anterior horn tears read on MRI, 85% involved the lateral meniscus anterior horn and about one half were judged to extend into the middle or body of the same meniscus. It splits into two bands at the PCL, named Humphry(anterior to the PCL) and Wrisberg (posterior to the PCL). The medial meniscus is more firmly attached to the tibia and capsule than the lateral meniscus, presumably leading to the increased incidence of tears of the medial meniscus [. On imaging alone, the radiologist may not be able to distinguish a residual tear (failed repair) from a recurrent tear in the same location. The incidence was calculated based on arthroscopic findings, and the potential secondary signs of meniscal ramp tears were evaluated on MRI. The shape of the meniscus is formed at the eighth week of These findings are also frequently associated with genu partly divides a joint cavity, unlike articular discs, which completely Radiology. meniscus is partial meniscal excision, leaving a 6- to 7-mm peripheral This case is almost identical to the previous case with a different clinical history. of the Wrisberg ligament in patients with a complete lateral discoid AJR American journal of roentgenology. It is often explained by fibers of the anterior cruciate ligament and the covering synovium . 5. {"url":"/signup-modal-props.json?lang=us"}, El-Feky M, Flipped meniscus - anterior horn lateral meniscus. Volunteerism and Sports Medicine: Where do We Stand? was saddle shaped. American Board of Orthopaedic Surgery Practice of the Orthopaedic Surgeon: Part-II, certification examination case mix. The patient underwent partial medial meniscectomy and ACL reconstruction. Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), Posterior Instability and Labral Pathology, Imaging Evaluation of the Painful or Failed Shoulder Arthroplasty, Other Entities: PLRI, HO, Triceps, and Plica, MRI-Arthroscopy Correlations in the Overhead Athlete, Acetabular Fossa, Femoral Fovea, and the Ligamentum Teres. The post arthrogram view (13B) reveals gadolinium within the repair site. Posterior root repair (Figure 16) is being performed with increasing frequency and has been shown to have better outcomes and decreased risk of osteoarthritis compared to posterior root tears treated non-operatively. {"url":"/signup-modal-props.json?lang=us"}, Weerakkody Y, Baba Y, Knipe H, et al. 2019: Factors associated with bilateral discoid lateral meniscus tear in patients with symptomatic discoid lateral meniscus tear using MRi and X-ray Orthopaedics and Traumatology Surgery and Research: Otsr 105(7): 1389-1394 70 year-old female with history of medial meniscus posterior horn radial tear. collapse and widening of the medial joint space (Figure 7). published a case series of anterior horn tears of the lateral meniscus in 14 soccer players (mean age 20.2 years). According to one source, they are thought to account for ~10% of all arthroscopic meniscectomies 5. found that the absence of a line of increased signal through the meniscus extending to the articular surface on proton density and T2-weighted images was a reliable MRI finding for an untorn post-operative meniscus with 100% sensitivity. MR arthrogram fat-suppressed sagittal T1-weighted image (11C) shows no gadolinium in the repair. A displaced longitudinal tear is a "bucket handle" tear. There is no universally accepted system for classifying meniscal tear patterns. The ends of the anterior and posterior horns are firmly attached to the tibia at their roots. What is your diagnosis? On the proton density-weighted image (12A) persistent high signal extends to the tibial and femoral surfaces (arrow). The most important clinical concern at the time of MRI imaging is often high-grade articular cartilage loss. Atypically thick and high location 2020;49(1):42-49. Because there is less pressure on the meniscus there, it is difficult to evaluate the anterior region of the meniscus. Radiographs may MRI Findings: Medial meniscus: Tear of the posterior horn seen to the inferior articular surface continuing into the posterior body and becoming more vertical. Results: Arthroscopic examination of the anterior horn of the lateral meniscus in all 22 patients was normal. The sagittal proton density-weighted image (2A) demonstrates increased signal intensity at the periphery of the medial meniscus posterior horn (arrow) but no fluid signal on the sagittal T2-weighted image (2B) and no gadolinium extension into this area on the MR arthrogram sagittal fat-suppressed T1-weighted arthrographic image (2C) consistent with a healed repair. Grade 3 is a true meniscus tear and an arthroscope is close to 100 percent accurate in diagnosing this tear. Bilateral hypoplasia of the medial meniscus has also been A meniscus is a crescent-shaped fibrocartilaginous structure that Diagnostic performance is decreased following partial meniscectomy since the standard criteria used to diagnose a meniscus tear cannot be applied to the post-operative meniscus.3,4,5,6 Partial meniscectomy may distort the normal morphology of the meniscus and increased meniscal signal intensity may extend to the articular surface when a portion of the meniscus has been resected, simulating a tear. In this case, having the prior MRI exam is useful for showing the location of the initial tear and the new tear in a different location. Monllau et al in 1998 proposed adding a fourth type, The meniscus root plays an essential role in maintaining the circumferential hoop tension and preventing meniscal displacement. horns to the meniscal diameter on a sagittal slice that shows a maximum The menisci are C-shaped fibrocartilaginous structures composed of radial and circumferential collagen fibers that have several roles, including joint stabilization, load distribution, articular cartilage protection and joint lubrication. Lateral meniscal variant with absence of the posterior coronary ligament. of these meniscal variants is the discoid lateral meniscus, and the Extrusion is commonly seen following root repair. An MRI of plaintiff's left knee conducted in May 2018 demonstrated a complex 7 tear of the posterior horn of the lateral meniscus and a suspected horizontal tear of the anterior horn of the lateral meniscus. For DSR inquiries or complaints, please reach out to Wes Vaux, Data Privacy Officer, tear. A 22-years old male presented with injury to right knee in a road traffic accident MRI images shows double posterior horn of lateral meniscus and absent anterior horn in coronal (A: PD; B: STIR; C . The lateral . The torn edges are aligned, and stable fixation applied with sutures or bioabsorbable implants at approximately 5 mm intervals. Longitudinal lateral meniscus tear status post repair (arrow). 15 year old patient with prior extensive lateral partial meniscectomy was treated with lateral chondroplasty and lateral meniscal allograft transplant with continued pain and clicking 6 weeks post-operative. . Lateral meniscus bucket handle tears can produce the double anterior horn sign or double ACL sign. A tear of the lateral meniscus can occur from a sudden injury, or from chronic wear and overload. The intrameniscal ligament where it diverges from the back of the anterior horn of the lateral meniscus is also a common area misinterpreted as a tear. We hope you found our articles Bilateral complete discoid medial menisci combined with anomalous insertion and cyst formation. Anterior horn lateral meniscus tear A female asked: Mri: "macerated anterior horn lateral meniscus with inferiorly surfacing tear. Intensity of signal contacting meniscal surface in recurrent tears on MR arthrography compared with that of contrast material. The articular cartilage is well seen on the pre-operative sagittal proton density-weighted image (19B). Suprapatellar plica noticed, with no related cartilaginous erosions. 7.2 Medial and Lateral Menisci Medial meniscus is larger than the lateral meniscus and is more "open" (=less C-like) and less wide. Shepard and colleagues at UCLA specifically analyzed this by reviewing 947 consecutive MRIs. Meniscal surgery is common and requires accurate post-operative imaging interpretation to guide the treatment approach. bilaterally absent menisci reported by Tolo et al,3 the Case study, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-75066. Cho JM, Suh JS, Na JB, et al. There described in thrombocytopenia absent radius syndrome (TAR syndrome).2,3 Bilateral hypoplasia of the medial meniscus has also been reported.4. They are usually due to an acute injury [. Among these 26 studies of an LMRT . Papalia R, Vasta S, Franceschi F, D'Adamio S, Maffulli N, Denaro V. Meniscal Root Tears: From Basic Science to Ultimate Surgery. This emphasizes the importance of baseline MRI comparison for evaluation of the postoperative meniscus.3. The Journal of bone and joint surgery American volume. attachment of the posterior horn is the Wrisberg meniscofemoral No gadolinium extension into the meniscus on fat-suppressed sagittal T1-weighted (9B) post arthrogram view. Unable to process the form. (1A) Proton density-weighted, (1B) T2-weighted, and (1C) fat-suppressed T1-weighted MR arthrographic sagittal images are provided. After preparing the recipient knee by creating a matching keyhole trough in the tibia, the surgeon slides the allograft bone plug into its matching tibial slot and sutures the periphery of the allograft meniscus to the capsule. and ACL tears can be mistaken for AIMM, but carefully tracing the However, many clinicians opt to use conventional MRI as the initial postoperative imaging study and reserve MR arthrography for equivocal cases. 2005; 234:5361. Magnetic resonance imaging (MRI) of both knee joints showed an almost complete absence of the anterior and posterior horns of the medial meniscus, except for the peripheral portion, hypoplastic anterior horns and tears in the posterior horns of the lateral meniscus in both knees (Fig. Development of the menisci of the human knee Menisci are present in the knees and the The intrameniscal ligament where it diverges from the back of the anterior horn of the lateral meniscus is also a common area misinterpreted as a tear. A 23-year-old female presented with a 2-month history of catching and pain in the knee when arising from a squatting position. Lateral meniscus posterior horn peripheral longitudinal tear managed by repair. of the distal femur and proximal tibia, and in the case report of Continuous meniscal tissue bridged the anterior and posterior horns of the lateral meniscus on 3 consecutive sagittal slices (Figure 1B). The most frequent symptom is pain that usually begins with a minor discoid lateral meniscus is a relatively uncommon developmental variant Repair techniques include inside-out, outside-in or all-inside approaches. small meniscus is also seen in the wrist joint. While they can arise from a number of mechanisms, root tears are generally thought to be chronic 5. Meniscal tears are common and often associated with knee pain. Each meniscus has three main parts, the back (posterior horn), middle (body), and front (anterior horn). Normal shape and signal of the horns of the medial meniscus, with no evidence of tears or degenerations seen. Anatomic variability and increased signal change in this area are commonly mistaken for tears. Clinical History: An 18 year-old male with a history of a posterior horn medial meniscus peripheral longitudinal tear treated with meniscal repair at age 16 presents for MR imaging. The diagnosis of tears of the anterior horn of the meniscus by magnetic resonance imaging (MRI) is sometimes different from that obtained by arthroscopic examination. an adult), and approximately twice the size of the anterior horn on A new longitudinal tear has occurred more centrally in the meniscus (arrowhead) with linear high signal extending to the tibial and femoral surfaces as well as fluid signal and gadolinium contrast in the defect. Rohren EM, Kosarek FJ, Helms CA. The lateral meniscus is more circular, and its anterior and posterior horns are nearly equivalent in size in cross section. He presented after a few months with symptoms of instability. Diagnosis - clinical presentation with exclusion of advanced knee osteoarthritis. On the sagittal proton density-weighted image (11A), signal contacts the tibial surface. Sagittal proton density-weighted image (5B) through the medial meniscus at age 17 reveals an incomplete tibial surface longitudinal tear (arrow) in a new location and orientation. You have reached your article limit for the month. According to these authors, increased signal to the surface on only one slice should be interpreted as a possible tear. Cases of only one abnormal slice correlated to tears at arthroscopy 55 % of the time for the medial meniscus and 30 % for the lateral [, Accuracy of diagnosing meniscus tear with these criteria has been good. 4. MRI showed posterior horn of the medial meniscus (PHMM) horizontal tear with early degenerative changes. Kim SJ, Choi CH. tissue only persists at the edges, where differentiation into the that this rare condition is also clinically asymptomatic. There is no telling how much this error rate will change for radiologists less experienced with MRI. The patient underwent a successful partial medial meniscectomy and was encouraged to seek low-impact exercise. discoid lateral meniscus, including a propensity for tears to occur and MRI of the knee is commonly indicated for evaluation of unresolved or recurrent knee pain following meniscal surgery. Arthroscopy: The Journal of Arthroscopic & Related Surgery. Schwenke M, Singh M, Chow B Anterior Cruciate Ligament and Meniscal Tears: A Multi-modality Review. 1 ). Medial meniscus posterior horn peripheral longitudinal tear treated with repair. The condition is typically asymptomatic and, therefore, is infrequently diagnosed.14 Posterior meniscal root repairs: outcomes of an anatomic transtibial pull-out technique. Following meniscal allograft transplantation (Figure 17), complications occur in up to 21% of procedures, including allograft failure and progressive cartilage loss.19 Repeat operations occur in up to 35% of patients, 12% requiring conversion to total knee arthroplasty. 1). Radiology. RESULTS. Problems encountered in a discoid medial meniscus are the same as a Symptoms of anterior horn tears were very similar to those of meniscal tears of the midbody or posterior horn, including catching, pain with knee flexion, and swelling. Sagittal proton density-weighted image (8A) through the medial meniscus demonstrates signal extending to the tibial surface (arrow). Examination showed lateral joint line tenderness and a positive McMurray sign. Mechanical rasping or trephination of the torn meniscus ends and parameniscal synovium is used to promote bleeding and vascular healing. At the time the article was created Yuranga Weerakkody had no recorded disclosures. A The same imaging criteria (as for the case of greater than 25% partial meniscectomy), the presence of fluid signal on T2-weighted or contrast extending into the meniscal substance is used to diagnose a recurrent tear. It is important to know the age of the patient when interpreting the MRI. De Smet A. Sagittal PD (. A meta-analysis of 44 trials. Increased signal intensity at the anterior horn of the lateral meniscus was seen on the images of seven of the 11 MR studies of the volunteers. The medial meniscus is asymmetrical with a larger posterior horn. You can use Radiopaedia cases in a variety of ways to help you learn and teach. Best assessed on T2 weighted sequences. meniscus are not uncommon; they include an anomalous insertion of the Stein T, Mehling AP, Welsch F, von EisenhartRothe R, Jger A. When interpreting MR images of the knee, it is important to assess for any change from the expected shape of the menisci. The MFL was not observed in five (19%) of 26 studies of an LMRT. | Semantic Scholar Significant increase in signal intensity at the anterior horn of the lateral meniscus near its central attachment site on sagittal magnetic resonance (MR) images of the knee is a normal finding. Similarly, the postoperative meniscus is at increased risk for a recurrent tear either at the same or different location due redistribution of forces and increased stress on the articular surface. Discoid lateral meniscus in children. Lee S, Jee W, Kim J. variant, and discoid medial meniscus. congenital absence of the cruciate ligaments. Repair devices including arrows, darts and sutures are used to approximate the torn edges of the meniscus. In the U.S., intraarticular injection of gadolinium-based contrast is off label. Kim SJ, Moon SH, Shin SJ. The lateral meniscus is produced by the varus tension and tibial IR. A slightly overweight 44-year-old male sought evaluation for medial knee pain that persisted for months after running on the beach. The examiner can test the entire posterior horn up to the middle segment of the meniscus using the IR of the tibia followed by an extension. menisci occurs. discoid meniscus, although discoid medial menisci can occur much less A 64-year-old female with no specific injury presented with knee pain, swelling, and locking that she first noticed after working out at the gym. An athletic 52-year-old male, who was an avid runner all his adult life, presented with medial pain and a popping sensation in knee. (Tr. Total meniscectomy is rarely performed unless the meniscus is so severely damaged that no salvageable meniscal tissue remains. show cupping of the medial tibial plateau, proximal medial tibial physis Conventional MRI is useful for evaluation of posterior root morphology at the tibial tunnel fixation site, meniscal extrusion and articular cartilage. How I Diagnose Meniscal Tears on Knee MRI. noted to be diminutive, with the posterior horn measuring 7 mm to 8 mm. Anomalous Their 74% false-positive rate I believe is accurate and one that we can incorporate mentally into our practice as we evaluate patients and the MRI scan results. On the sagittal fat-suppressed T2-weighted image (7B), fluid extends into the tear. Most studies have shown increased accuracy for direct and indirect MR arthrography compared to conventional MRI for partial meniscectomies of 25% or more.16. The fat-suppressed sagittal T1-weighted post arthrogram view (7C) demonstrates gadolinium extending into the meniscal substance. Damaged meniscal tissue is removed with arthroscopic instruments including scissors, baskets and mechanical shavers until a solid tissue rim is reached with the meniscal remnant contoured, preserving of as much meniscal tissue as possible. Nakajima T, Nabeshima Y, Fujii H, et al. Normal course and intensity of both cruciate ligaments. The anomalous insertion the intercondylar notch, most commonly to the mid ACL, and less commonly does not normally occur.13. However, the tear changes plane of orientation over its course. What is a Grade 3 meniscus tear? snapping knee due to hypermobility. Discoid medial menisci are much less common than discoid lateral menisci,24 and they may be bilateral. A Study of Retrieved Allografts Used for ACL Surgery, Long-Term Results of Meniscus Allograft Transplantation with Concurrent ACL Reconstruction, Anterior Horn Meniscal Tears — Fact or Fiction, How Triathletes Can Use Cycling Cadence to Maximize Running Performance, Pharmacology Watch: HRT - Position Paper Places Benefits in Question, Clinical Briefs in Primary Care Supplement. The sutures are tied over a cortical fixation device or Endobutton (short arrow) with the knee flexed at 90 to secure the root repair. Extension to the anterior cortex of . 3: The Wrisberg variant, where the meniscus may have a normal Thirty-one of these patients underwent subsequent arthroscopic evaluation to allow clinical correlation. To assess the prevalence of meniscal extrusion and its . sagittal magnetic resonance (MR) images. Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-40036, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":40036,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/meniscal-root-tear/questions/1112?lang=us"}. Also, the inferior patella plica inserts on the If a meniscus tear shows up on a MRI, it is considered a Grade 3. (PubMed: 17114506), BakerJC, FriedmanMV, RubinDA (2018) Imaging the postoperative knee meniscus: an evidence-based review. 6. 3. (middle third), or Type 3 (superior third; intercondylar notch) (Figure Associated anomalies in a discoid medial Symptomatic anomalous insertion of the medial meniscus. In cases like this, MR arthrography is quite helpful. Synopsis: In a consecutive series of nearly 1000 knee MRIs, there was a 74% false-positive rate for the diagnosis of anterior horn meniscal tears. Rao PS, Rao SK, Paul R. Clinical, radiologic, and arthroscopic assessment of discoid lateral meniscus. On MR images of the knee it is sometimes impossible to determine with confidence if a focus of high signal in the meniscus is confined to the substance of the meniscus or if it extends to involve the surface. the posterior horn is usually much larger than the anterior horn (the On examination, there was marked medial joint line tenderness and a large effusion. The MRI sign of a radial tear is a linear, vertical cleft of abnormal high signal at the free edge (Fig. Criteria for a recurrent tear after greater than 25% meniscectomy Definite surfacing T2 fluid signal (or high T1 signal isointense to intra-articular gadolinium on MR arthrography) on 2 or more images or displaced meniscal fragment.17 Definite surfacing fluid signal on only one image represents a possible tear. In this case, the patient never obtained relief from the initial surgery, and the surgeon felt this was a residual tear (failed repair) rather than a recurrent tear. meniscal diameter. 2012;199(3):481-99. this may extend to to the mid body." is this a bucket tear? hypermobility. Of those 31 patients who underwent arthroscopic examination, there were only 8 true anterior horn tears (26% true positive rate) and 18 had normal or intact menisci in all zones. Regardless of the imaging protocol chosen for evaluation of the postoperative meniscus, optimal imaging interpretation includes: The normal MRI appearance after partial meniscectomy is volume loss and morphologic change, commonly truncation or blunting of the meniscal free edge. Connolly B, Babyn PS, Wright JG, Thorner PS. mimicking an anterior horn tear. Conventional MRI imaging of the postop meniscus offers a noninvasive evaluation of the knee, but postoperative changes can mimic a recurrent or residual meniscus tear. to the base of the ACL or the intercondylar notch. Both ligaments attach distally to the posterior horn of the lateral meniscus and contribute to posterior drawer stability . CT arthrography is a recommended alternative for patients who are not MR eligible. The Wrisberg variant may present with a diminutive (1 mm) with no increased signal to suggest root attachment varus deformity (Figure 3). Repair of posterior root tears are being performed with increased frequency over the past several years. Discoid lateral meniscus was originally believed to result from an The anterior meniscofemoral ligament (Humphrey ligament) attaches proximally on the medial femoral condyle, inferior to the PCL insertion. The speckled appearance of the anterior horn of lateral meniscus is a feature that can be seen as a normal variant on MRI knee scans. Meniscal transplants can fail at the implantation site by avulsion, failure of bone plug incorporation or bone bridge fracture. Magnetic resonance imaging (MRI) revealed an elongated free edge of the diffusely enlarged lateral meniscus extending toward the intercondylar region on coronal T1-weighted images (Figure 1A). Discoid medial meniscus. The aim of this study was to evaluate diagnostic values involved in conventional magnetic resonance imaging (MRI) features of MM posterior root tears (MMPRTs) and find other MRI-based findings in patients with partial MMPRTs. An alternative way of fastening the allograft to the donor knee involves harvesting the meniscus with a small bone plug attached to each root and then securing the plugs within osseous tunnels drilled in the recipient tibia. The reported prevalence is 0.06% to 0.3%.25 meniscal injury. This patient had relief after the initial repair surgery, then had a second injury with recurrent symptoms, which is why the surgeon felt this was a recurrent tear. The lateral meniscus is more circular, and its anterior and posterior horns are nearly equivalent in size in cross section. At the time the case was submitted for publication Mostafa El-Feky had no recorded disclosures. The MRI also demonstrated moderate degenerative spurring at the lateral joint compartment, a large knee joint effusion with . The lateral meniscus is more circular with a shorter radius, covering 70% of the articular surface with the anterior and posterior horns approximately the same size. CT arthrography may be used to evaluate the postoperative meniscus when MRI is contraindicated. Tears of the anterior horn of the medial meniscus, an inferior patella plica, and ACL tears can be mistaken for AIMM, but carefully tracing the ligament will help to exclude these conditions. MRI appearance of Wrisberg variant of discoid lateral meniscus. MRI features are consistent with torn lateral meniscus with flipped anterior horn superomedial and posterior, resting superior to the posterior horn. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. Root tears are often large radial tears that extend through the entire AP width of the meniscus.