Discoid meniscus: current concepts

Characteristics and Outcomes of Operatively Treated Discoid Lateral Meniscus in Pediatric and Young Adult Patients: A Multicenter Study

BACKGROUND

Discoid lateral meniscus (DLM) is the most common congenital abnormality of the meniscus. Tears are common; treatment is frequently not definitive, often requiring reoperation.

PURPOSE

To report the clinical manifestations, physical characteristics, operative treatments and findings, complications, and reoperations of DLM in pediatric patients from multiple centers across North America.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Consecutive patients who underwent treatment for symptomatic DLM at 9 institutions between 2000 and 2020 were included. Patient data, presenting symptoms and signs, surgical findings, treatments rendered, and postoperative complications, including reoperation rates, were collected. Means with ranges and counts with proportions are reported for continuous and categorical variables, respectively, and comparisons were made using either the chi-square or Fisher exact test.

RESULTS

In total, 784 patients (867 knees) were included with a mean age at diagnosis of 12 years (range, 1-22 years) and a mean follow-up of 22.6 months (range, 0-154 months). Common preoperative symptoms were locking (33%) and snapping (30%). At surgery, tears in the DLM were present in 647 knees (594 patients [76%]); 95 knees (11%) had multiple tears; and in 140 knees, tears extended into >1 zone. Tears, when present, were more common within the posterior horn (41%) or body (34%) than the anterior horn (25%). Peripheral rim instability was reported in 241 knees (28%). Significantly more knees had instability posteriorly (15%; P = .0004) and anteriorly (9%; P = .0013) than along the body (3%). Tear type was most commonly complex (38%) or horizontal (34%). A total of 358 knees in 333 patients with tears (42% of all patients) underwent repair (55% of knees with tears). A total of 175 complications were reported, occurring in 139 knees in 134 patients (17%); 116 of these knees with complications (83%) had a single complication, while 23 (17%) had >1. Of the 784 patients, 105 (13%) underwent reoperation, undergoing 135 additional procedures related to their DLM. Of those, 60 (44%) were repeat arthroscopy and meniscal trim; 40 (30%), arthroscopy and meniscal repair; and 17 (13%), an articular cartilage procedure.

CONCLUSION

Locking and snapping were common presenting symptoms. Over three-quarters of patients had meniscal tears, which were most often complex and located posteriorly. Seventeen percent of patients experienced complications, and a sixth of patients with complications had >1. Reoperation was typically for persistent symptoms or meniscal retear.

Clinical efficacy and pain follow-up after arthroscopic discoid meniscoplasty of the knee: a retrospective study

BACKGROUND

To assess the viability and efficiency of performing arthroscopic meniscoplasty in treating discoid meniscus (DM) in the knee joint.

METHODS

A total of 29 patients diagnosed with symptomatic lateral DM between October 2014 and December 2019 were included in the study. Among them, 7 patients with intact DM underwent arthroscopic discoid meniscoplasty (group A), while 22 patients with torn DM received arthroscopic DM plasty along with repair and suturing (group B). Both Visual Analog Scale (VAS) score and Lysholm score assessments were conducted preoperatively and postoperatively.

RESULT

The favorable and acceptable outcome rate was 85.71% in group A and 95.45% in group B (P > 0.05). The VAS scores post-operatively at each follow-up time point were consistently lower compared to pre-operative values, while the Lysholm knee function scores showed improvement. There were no significant differences in VAS score and Lysholm score between group A and group B at different stages (P > 0.05). Both surgical techniques (discoid meniscoplasty and discoid meniscoplasty combined with repair and suture) showed significant improvement in postoperative VAS score and Lysholm score, but there was no difference in outcomes between the two groups.

CONCLUSION

Overall, the two surgical techniques studied in this study (discoid meniscoplasty and discoid meniscoplasty combined with repair and suture) produced similar results in terms of pain reduction and improved knee function.

Discoid meniscus: Treatment considerations and updates

A discoid meniscus is a morphological abnormality wherein the meniscus loses its normal 'C' shape. Although most patients are asymptomatic, patients might still present with symptoms such as locking, pain, swelling, or giving way. Magnetic resonance imaging is usually needed for confirmation of diagnosis. Based on a constellation of factors, including clinical and radiological, different approaches are chosen for the management of discoid meniscus. The purpose of this review is to outline the treatment of discoid meniscus, starting from conservative approach, to the different surgical options for this condition. The PubMed and Google Scholar databases were used for this review. Studies discussing the treatment of discoid meniscus from 2018 to 2023 were searched. Initially there were 369 studies retrieved, and after removal of studies using the exclusion criteria, 26 studies were included in this review. Factors such as stability, presence of tear, and morphology can help with surgical planning. Many approaches have been used to treat discoid meniscus, where the choice is tailored for each patient individually. Postoperatively, factors that may positively impact patient outcomes include male sex, body mass index < 18.5, age at symptom onset < 25 years, and duration of symptoms < 24 months. The conventional approach is partial meniscectomy with or without repair; however, recently, there has been an increased emphasis on discoid-preserving techniques such as meniscoplasty, meniscopexy, and meniscal allograft transplantation.

Posterior cruciate ligament tibial attachment sacrifice percentage is higher in cruciate-retaining total knee arthroplasty in patients with discoid lateral meniscus

BACKGROUND

The posterior cruciate ligament (PCL) attachment may be damaged in cruciate-retaining total knee arthroplasty (CR-TKA) using the complete resection for tibial preparation, and resection amount varies greatly among individuals. Discoid lateral meniscus (DLM) is one of the most common anatomic knee variants. This study aimed to evaluate the difference in PCL attachment sacrifice in CR-TKA between patients with and without DLM.

METHODS

Fifty-one knees in the study group (DLM group) were matched 1:1 to 51 control knees (non-DLM group) by age, sex, and maximum width of the tibial plateau. The percentage of the sacrificed PCL attachment and the morphological parameters of the tibial plateau were evaluated using magnetic resonance imaging (MRI) in a blind manner.

RESULTS

With a tibial cut simulated at a 0°, 3°, and 7° osteotomy slope, the mean PCL attachment resection percentages in the non-DLM group were 40.5%, 53.6%, and 72.6%, respectively. The corresponding resection percentages in the DLM group were 61.0% (P < 0.001), 73.3% (P < 0.001), and 85.7% (P < 0.001), respectively. The percentage of the minimum meniscus width to the maximum tibia width showed a weak positive correlation with the percentage of PCL attachment sacrifice.

CONCLUSIONS

A significantly greater portion of PCL attachment was sacrificed in DLM patients undergoing CR-TKA using the complete proximal tibia resection. Attention should be paid to PCL attachment resection during CR-TKA in patients with DLM, and alternative techniques or prosthesis types should be considered.

Patient-Reported Outcomes After Surgically Treated Anterior Horn Tears in the Pediatric Discoid Meniscus

Background

As a subset of symptomatic discoid lateral meniscal (DLM) tears, anterior horn (AH) meniscal tears are not well studied in the pediatric population. There are even fewer studies reporting patient-reported outcomes after surgical treatment of AH tears in DLM.

Purpose

To compare reported outcomes after surgical treatment of DLM tears involving the AH versus other locations in pediatric patients.

Study Design

Cohort study; Level of evidence, 3.

Methods

A retrospective review of prospectively collected patient data between 2013 and 2020 was conducted. Patients aged <18 years who underwent arthroscopic treatment of a symptomatic DLM were included. Pathology was classified as tears of the AH or tears not involving the anterior horn (NAH). Demographic data along with patient-reported outcome scores (Pediatric International Knee Documentation Committee [Pedi-IKDC] and Patient Assessment Questionnaire [PAQ]) were collected preoperatively through 24 months of follow-up.

Results

A total of 41 patients were included (median age, 12.9 years; range, 7-17 years; 32% female, 68% male). The mean follow-up time for was 25 months (range, 8-58 months). There were 17 (41%) patients in the AH group and 24 (59%) patients in the NAH group. Of the AH group, 16 (94%) were treated with meniscal repair (vs menisectomy), while 19 (79%) of the NAH group were treated with meniscal repair. All patients achieved significant pre- to postoperative improvement on both the Pedi-IKDC and the PAQ. At 24-month follow-up, there were no differences between the AH and NAH groups on the Pedi-IKDC (92.51 vs 89.72; P = .18) or the PAQ (2.57 vs 2.61; P = .06).

Conclusion

Patients who underwent meniscal repair for AH DLM reported positive postoperative outcomes.

Osteoarthritis Development Following Meniscectomy vs. Meniscal Repair for Posterior Medial Meniscus Injuries: A Systematic Review

This systematic review aims to evaluate critically and synthesize the existing literature on the outcomes of meniscectomy versus meniscal repair for posterior medial meniscus injuries, with a focus on osteoarthritis (OA) development. We sought to assess the incidence of OA following both treatment modalities, compare functional outcomes post-treatment, and identify factors influencing treatment choice, providing evidence-based recommendations for clinical decision-making. A comprehensive search strategy was employed across PubMed, Scopus, and Embase up until December 2023, adhering to PRISMA guidelines. The primary outcomes included OA development, functional knee outcomes, and quality of life measures. Six studies met the inclusion criteria, encompassing 298 patients. The systematic review revealed a significant association between meniscal repair and decreased progression of OA compared to meniscectomy. Meniscectomy patients demonstrated a 51.42% progression rate towards OA, significantly higher than the 21.28% observed in meniscal repair patients. Functional outcomes, as measured by the International Knee Documentation Committee (IKDC) and Lysholm scores, were notably better in the repair group, with average scores of 74.68 (IKDC) and 83.78 (Lysholm) compared to 67.55 (IKDC) and 74.56 (Lysholm) in the meniscectomy group. Furthermore, the rate of complete healing in the repair group was reported at 71.4%, as one study reported, indicating a favorable prognosis for meniscal preservation. However, these pooled data should be interpreted with consideration to the heterogeneity of the analyzed studies. Meniscal repair for posterior medial meniscus injuries is superior to meniscectomy in preventing OA development and achieving better functional outcomes and quality of life post-treatment. These findings strongly suggest the adoption of meniscal repair as the preferred treatment modality for such injuries, emphasizing the need for a paradigm shift in clinical practice towards preserving meniscal integrity to optimize patient outcomes.

[Application of anterior region suture of popliteal hiatus in treatment of discoid lateral meniscus injury with instability in popliteal tendon region]

Objective

To discuss the application of anterior region suture of the popliteal hiatus (PH) under arthroscopy in the treatment of discoid lateral meniscus (DLM) injury with instability in the popliteal tendon region.

Methods

The clinical data of 53 patients (56 knees) with DLM injury who met the selection criteria between March 2014 and November 2022 were retrospectively analyzed. There were 15 males and 38 females, aged 8-55 years with an average age of 36.5 years. Fourteen cases had a history of trauma, while the remaining 39 cases had no clear history of trauma. The disease duration ranged from 1 day to 6 years, with an average duration of 15.6 months. According to the Watanabe classification, there were 40 knees of complete type and 16 knees of incomplete type. The preoperative International Knee Documentation Committee (IKDC) knee joint score was 51.2±8.3, the Lysholm score was 59.6±11.2, and the visual analogue scale (VAS) score was 4.7±1.3. After the arthroscopic meniscal plasty, the instability of the popliteal tendon region meniscus was checked by probing traction. Subsequently, the Out-inside technique or a combination of Out-inside and All-inside techniques was used to suture the anterior region of the PH. The stability of the meniscus after suturing was assessed, and if necessary, further suturing using the All-inside technique at the posterior region of the PH, the posterior horn of the meniscus, and using the Out-inside technique at the anterior horn of the meniscus was performed. Postoperative complications were recorded. The effectiveness was evaluated using pre- and post-operative IKDC scores, Lysholm scores, and VAS scores.

Results

After operation, knee joint pain, crepitus, and locking disappeared, with McMurray and grinding tests turning negative. All patients were followed up 12-93 months with an average of 57.5 months. There was no complication such as common peroneal nerve injury, deep vein thrombosis of the lower limbs, joint infection, or joint stiffness. At last follow-up, the IKDC knee joint score was 76.7±5.5, the Lysholm score was 94.0±4.1, and the VAS score was 1.1±0.8. The differences compared with preoperative scores were significant ( t=-22.090, P<0.001; t=-23.704, P<0.001; t=19.767, P<0.001).

Conclusion

Suturing of the anterior region of the PH is crucial in the treatment of DLM injury with instability in the popliteal tendon region.

Discoid Double-layered Lateral Meniscus: A Case Report

Introduction

Abnormalities of the double-layered meniscus are rare and can be difficult to diagnose. The main pathology in this abnormality, which is predominantly seen in the lateral compartment, is an accessory meniscus lying over the normal meniscus. Anatomically, this structure can appear in different forms. Although other meniscal abnormalities associated with a double-layered meniscus have been reported, this case presents a previously undescribed type in the literature.

Case Report

A 12-year-old girl presented to our clinic with complaints of knee locking and pain. When the patient underwent arthroscopy, an accessory incomplete discoid meniscus was found overlying the normal lateral meniscus. We performed an excision of the upper accessory meniscus and the patient had no problems during 3 years of follow-up after surgery.

Conclusion

Abnormalities of the lateral meniscus are rare and can be difficult to diagnose. In cases where we suspect a meniscal abnormality, a proper arthroscopic examination should be performed and if a discoid meniscus is seen, it should be considered that this may be a double-layered meniscus.

Age-based comparison of meniscal dimensions between an asymptomatic complete discoid lateral meniscus and normal meniscus: MRI evaluation

INTRODUCTION

This study aimed to evaluate the meniscal size of asymptomatic discoid lateral meniscus (DLM) and compare it with that of normal lateral meniscus (LM) and to compare changes in meniscal dimensions with age among patients with asymptomatic DLM and those with normal LM using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively reviewed the medical records, including MRI data, of patients with asymptomatic DLM (DLM group) or normal LM (control group). Width and extrusion of both DLM and normal LM and tibial length were measured and compared using mid-coronal and mid-sagittal MR images. Meniscal size and sagittal and coronal meniscal ratio according to age, as well as differences between DLM and normal menisci, were also evaluated.

RESULTS

Thirty-four knees were included in the DLM group, whereas the control group comprised of 50 patients. The DLM group showed significantly less meniscal extrusion, greater coronal width, posterior capsule distance, sagittal meniscal length, and sagittal meniscal ratio than the control group (DLM: 0.1 ± 0.3 mm, 23.3 ± 2.2 mm, 5.4 ± 2.4 mm, 25.1 ± 2.8 mm, 61 ± 6%, and control: 0.4 ± 0.4 mm, 9.5 ± 2.3 mm, 2.5 ± 1.2 mm, 30.2 ± 2.6 mm, 71 ± 4%, respectively). The coronal meniscal ratio decreased with age in both the control (p = 0.001) and DLM (p = 0.037) groups. The sagittal meniscal ratio (p = 0.001) and minimum height (p = 0.04) decreased and the anterior capsule distance (p = 0.035), posterior capsule distance (p = 0.026), and entire sagittal length (p = 0.005) increased with age in the DLM group, while the distance between the meniscal inner margins (p = 0.019) increased with age in the control group.

CONCLUSIONS

The meniscal ratio in the sagittal plane of the DLM group was significantly lower than that of the control group. The sagittal meniscal ratio of asymptomatic DLM decreased with age, indicating that the size of asymptomatic DLM does not change with age.

LEVEL OF EVIDENCE

III: Retrospective comparative study.

Prevalence and a correlation analysis of discoid meniscus and femoral trochlear dysplasia

BACKGROUND

Discoid meniscus (DM) and femoral trochlear dysplasia (FTD) are common knee disorders. Both as congenital malformation, whether there is a connection between them is unclear and the research on their prevalence in the general population is inadequate. This study aimed to investigate the prevalence of FTD and DM in the general population through a large sample size, and to explore the relationship between them.

STUDY DESIGN

Retrospective study.

METHODS

Patients undergoing knee magnetic resonance imaging (MRI) examinations at our outpatient clinic were screened and 1003 patients were enrolled in DM group with 989 patients in non-DM (NDM) group. The type of DM and FTD was classified with Watanabe classification and Dejour's classification, respectively. The prevalence of FTD and DM in the general population and the relationship between them were evaluated.

RESULTS

The prevalence of DM and FTD was 10.0% and 14.5%, respectively. The overall percentage of FTD was higher in DM group (P < 0.001). The DM group has a higher percentage of all types of FTD except type D (P < 0.05), and a higher percentage of both low- and high-grade FTD (P < 0.001). There were 633 cases of type I DM and 370 cases of type II DM. The overall percentage of FTD was not significantly different between the two types (P = 0.106). No significant difference was detected for all types of FTD except type B (P < 0.05). The Type I DM group has a significant higher percentage of high-grade FTD than Type II group (P < 0.05).

CONCLUSION

Patients with a DM are more likely to have FTD regardless of the type of DM, while those with a type I DM are more prone to have a high grade FTD.

A Torn Discoid Lateral Meniscus Impacts Lower-Limb Alignment Regardless of Age: Surgical Treatment May Not Be Appropriate for an Asymptomatic Discoid Lateral Meniscus

BACKGROUND

A discoid lateral meniscus (DLM) is more prone to tear, and treatment of this condition is challenging. The purpose of the present study was to investigate (1) whether a torn DLM is associated with more varus alignment than a torn semilunar lateral meniscus (SLM) and (2) whether the lower-limb alignment associated with a torn DLM changes with age.

METHODS

Consecutive patients who underwent arthroscopic knee surgery for a torn lateral meniscus were included. Patients with a torn DLM (confirmed on arthroscopy) were allocated to the DLM group; those with a torn SLM were allocated to the SLM group. After strict screening according to the inclusion and exclusion criteria, 436 and 423 patients were included in the DLM and SLM groups, respectively. The mechanical axis deviation (MAD), hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle, and medial proximal tibial angle were compared between the 2 groups after propensity score matching. Additionally, the correlation of the HKA and MAD with age was evaluated within the DLM group.

RESULTS

After propensity score matching, all baseline characteristics were well balanced between the 2 groups. The DLM group had significantly more varus alignment than the SLM group (MAD: 3.6 mm ± 9.6 mm versus 1.1 mm ± 10.3 mm, respectively, p = 0.001; HKA: 179.1° ± 2.9° versus 179.9° ± 3.0°, respectively, p = 0.001). Within the DLM group, the MAD (R = 0.10, p = 0.032) and HKA (R = -0.13, p = 0.007) had a weak correlation with age.

CONCLUSIONS

Patients with a torn DLM had more varus knee alignment than those with a torn SLM, and this trend did not increase with age after minimizing the effects of osteoarthritis. Therefore, surgical treatment may not be appropriate for asymptomatic DLM.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Feasibility and efficacy of ultrasound in the diagnosis of discoid lateral meniscus and its classification in children: protocol for a prospective, multicentre, diagnostic test study

INTRODUCTION

Although ultrasound can reportedly diagnose discoid lateral meniscus (DLM) in children, its widespread application is challenging because the diagnostic criteria are based on qualitative descriptions of DLM morphology rather than quantitative parameters. Additionally, no studies have applied ultrasound in classifying DLM. Therefore, this study aims to establish the quantitative ultrasound parameters that reflect DLM morphology, evaluate the feasibility and validity of these parameters for identifying DLM and their classification, and develop the quantitative ultrasound diagnostic criteria for DLM and their classification in children.

METHODS AND ANALYSIS

Patients will be recruited from the outpatient clinics of the orthopaedics department at West China Hospital, Sichuan University, the Fourth Medical Center of the Chinese People's Liberation Army General Hospital, Xinhua Hospital affiliated with Shanghai Jiao Tong University School of Medicine, Yibin Hospital affiliated with West China Hospital Sichuan University, Suining Central Hospital and the Third Hospital of Mianyang from August 2022 to July 2024. Eligible patients are those aged ≤14 years, with knee symptoms such as pain, locking and limited extension, and who planned to undergo arthroscopic surgery. Exclusion criteria are patients with contraindications to ultrasound examination, such as severe skin damage or fracture around the knee. The sample size is estimated to be 576 cases with a power of 0.9 for hypothesis testing, a two-sided α of 0.05, and an expected sensitivity and specificity of 95%. Three days before surgery, ultrasound will be used to observe the morphology of the lateral meniscus and measure its width, angle α formed by the chord of upper and lower arc-shaped articular surface at the free edge, and the movement distance of the peripheral rim. Participants will be categorised according to the arthroscopy results for the DLM and its classification. The diagnostic performance of each parameter will be assessed and compared in terms of the area under the curve, sensitivity, specificity, and positive and negative predictive values.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of West China Hospital, Sichuan University (approval no. 2022-923), and this approval covers all study hospitals. Written informed consent is required from all participants before enrolment in the study. The study's findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry (ChiCTR2200062000).

Meniscal Allograft Transplants in Skeletally Immature Patients: A Systematic Review of Indications and Outcomes

Meniscal lesions in skeletally immature patients can lead to joint degradation and knee instability. Meniscal allograft transplant (MAT) surgery is a solution to maintain knee stability. There is a lack of consensus on MAT surgery outcomes in pediatric patients. A systematic review was conducted according to the PRISMA guidelines. PubMed, Scopus and EMBASE databases were searched from 1965 to June 2022. Studies were evaluated using the Newcastle-Ottawa Scale (NOS). Three studies were selected, and 58 patients were included (mean age 15.9 years) in total. The lateral meniscus was involved in 82.8% of all MAT surgeries. Post-meniscectomy syndrome and discoid meniscus were the main indications for MAT surgery. All studies reported improved subjective clinical scores and levels of sport after the surgery. The complication rate was 27.5%. Partial meniscectomy, meniscus knot removal, chondral defect treatment and lysis of adhesions were the most frequent procedures performed during reoperation. MAT surgery can improve clinical outcomes in pediatric patients with strictly selected indications. MAT surgery is safe when there are no limb asymmetries or malalignments, but it remains a challenging procedure with a high complication rate. Long-term follow-up is needed for definitive statements on the use of MAT in skeletally immature patients.

Patients with discoid menisci have similar clinical outcomes to those without discoid menisci when undergoing surgical intervention: a systematic review

PURPOSE

To compare post-operative clinical outcomes of discoid meniscus tear procedures such as saucerization with or without repair with those of non-discoid meniscus tears such as meniscectomy or repair in skeletally mature patients with no concomitant injuries.

METHODS

Three databases MEDLINE, PubMed and EMBASE were searched from inception to July 3rd, 2022 for literature describing patient-reported outcome measures after meniscus surgery in discoid or non-discoid meniscus tears. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Clinical outcome data on Lysholm, Tegner, International Knee Documentation Committee (IKDC), revision rates, and complications were recorded, with MINORS and Detsky scores used for quality assessment.

RESULTS

A total of 38 studies comprising 2213 patients were included with a mean age of 38.6 years (range: 9.0-64.4). The mean follow-up time was 54.1 months (range: 1-234) and the average percentage of female participants was 46.8% (range: 9.5-95.5). The mean change between pre-operative and post-operative Lysholm scores ranged from 21.0-39.0, 7.4-24.1, and 24.2-48.4 in the discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. The mean change in Tegner scores ranged from 0.0 to 2.3, 1.3, and 0.4-1.3 in the discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. Pre-operative IKDC scores were not reported, however mean post-operative IKDC scores ranged from 77.4 to 96.0, 46.9 to 85.7, and 63.1 to 94.0 in discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. Revision rates for discoid procedures, non-discoid meniscectomies, and non-discoid meniscus repairs ranged from 3.2 to 44.0%, 8.3 to 56.0%, and 5.9 to 28.0%, respectively. The most common reasons for revision were acute trauma and persistent pain.

CONCLUSION

Discoid saucerization procedures with or without repair leads to similar Lysholm scores as non-discoid repair procedures, and similar IKDC scores and revision rates compared to non-discoid meniscectomy or repair procedures. Patients undergoing discoid procedures appeared to have slightly higher Tegner activity scores compared to patients undergoing non-discoid procedures; however this is to be considered in the context of a younger population of patients undergoing discoid procedures than non-discoid procedures. This information can help guide surgeons in the decision-making process when treating patients with discoid menisci, and should guide further investigations on this topic.

LEVEL OF EVIDENCE

IV.

Imaging of Anatomical Variants Around the Knee

Several anatomical variants have been described in the knee. These variants may involve intra- and extra-articular structures, such as menisci, ligaments, plicae, bony structures, muscles, and tendons. They have a variable prevalence, are generally asymptomatic, and are usually discovered incidentally in knee magnetic resonance imaging examinations. A thorough knowledge of these findings is essential to avoid overestimating and overinvestigating normal findings. This article reviews most anatomical variants around the knee, describing how to avoid misinterpretation.

Ontogeny of the meniscus in the anuran Xenopus laevis

The anuran knee joint is subjected to the jump, one of the tetrapods' most demanding mechanical stresses. Consistent with this continuous effort, the knee of the anurans has a complex structure comparable to that of an amniote. Here, we describe the ontogeny of the Xenopus knee tissues and study the morphogenesis of the knee joint shape by performing a geometric morphometric analysis of specially selected anatomical structures: the menisci and the long bone epiphyses. A meniscus is a crescent-shaped fibrocartilaginous structure, with a triangular cross-section inserted between joints surfaces. A meniscus transmits load across the tibiofemoral joint by increasing congruity of the long bone epiphysis and decreasing the resulting stress exerted on the articular cartilage. We ask two questions: (1) what is the tissue composition along the ontogeny of the menisci of a swimming frog? (2) How do the menisci acquire the shape that will allow their adjustment? We studied the structures and tissue ontogeny of the knee of several specimens of Xenopus laevis and evaluated the congruity of the knee structures across the species ontogeny. Histological sections showed that the cavitation process responsible for separating the menisci and the epiphyses seems to be pivotal in shaping the conformity of these structures and the long bone epiphyses of the hindlimbs. The geometric morphometric analysis allowed us to interpret three phases of differentiation associated with limb functionality. The characteristic shape of the meniscus appears early in the ontogeny of the knee, simultaneously with the epiphysis contours.

Evaluation of tibial eminence morphology using magnetic resonance imaging (MRI) in juvenile patients with complete discoid lateral meniscus

Background

Many studies have shown that hypoplasia of knee bone morphology is related to the morphological features of the discoid lateral meniscus (DLM). However, few studies have focused on hypoplasia of tibial eminence morphology in juvenile patients with complete DLM. The purpose of this study was to determine the relationship between tibial eminence morphology characteristics and complete DLM in juvenile patients.

Methods

The DLM group comprised 34 juvenile patients with complete DLM, and the control group comprised 34 juvenile individuals, each with a normal lateral meniscus based on magnetic resonance imaging (MRI) findings. All parameters, including tibial width (TW), tibial eminence width (TEW), the height of the lateral tibial spine (HLTS), the height of the medial tibial spine (HMTS), lateral slope angle of the lateral tibial eminence (LSALTE), lateral slope angle of the medial tibial eminence (LSAMTE), tibial eminence width ratio (TEWR), height of the lateral tibial spine ratio (HLTSR), and the height of the medial tibial spine ratio (HMTSR), were recorded using coronal MR images. Statistical analyses were used to determine the differences between the two groups and whether differences were significant.

Results

The TEW and TEWR were significantly greater (P < 0.05), and LSALTE and LSAMTE were significantly smaller (P < 0.05) in patients in the DLM group than in participants in the control group. Receiver operating characteristic (ROC) analysis revealed that a larger TEW, above 13.4 mm, was associated with complete DLM, with a sensitivity of 77.0% and specificity of 88.2%, and a larger TEWR, above 19.7%, was associated with complete DLM, with a sensitivity of 76.5% and specificity of 91.2%.

Conclusions

MR imaging can be used to diagnose tibial eminence hypoplasia in juvenile patients with complete DLM. Additionally, TEW and TEWR could help clinicians screen for complete DLM in juvenile patients.

The discoid lateral meniscus in children: a narrative review of pathology, diagnosis and treatment

Background and Objective

The discoid lateral meniscus (DLM) is a congenital abnormality of the meniscal shape, characterized by a typical central hypertrophy and a diameter larger than a regular meniscus, potentially leading to knee pain and symptoms, especially in children. The present study provides an update and a general review of this uncommon meniscal pathology. The incidence of discoid meniscus is about 0.4-17% for the lateral and 0.1-0.3% for the medial, although, being often asymptomatic, the true prevalence is unknown. We aim to enhance awareness on this subject to medical care provider.

Methods

A literature search was performed on PubMed, including articles written in English until October 2021.

Key Content and Findings

The articles regarding etiology, diagnosis and management of DLM in children or in patients younger than 18 years were reviewed using the narrative approach.

Conclusions

Recent literature has shown that DLM is one of the most frequent congenital anomalies of the knee encountered during childhood. While asymptomatic children with incidental finding can be managed nonoperatively, symptomatic painful DLM should be addressed surgically, restoring typical anatomy using saucerization, tear repair, and stable fixation of the meniscus. The risk of osteoarthritis progression seems to be higher in children with operated DLM, imposing prolonged follow-up and cartilage preserving strategies for these patients.

Young Children with a Bucket-Handle Tear to the Discoid Lateral Meniscus Successfully Treated Using Arthroscopic Saucerization and Repair: Two Case Reports

Observations of a symptomatic discoid lateral meniscus in young children are infrequent. The objective of this report was to demonstrate the use of arthroscopic saucerization and repair for treating a bucket-handle tear of a lateral discoid meniscus in two young children. Two young children (a 28-month-old girl and a 5-year-old boy) presented with a bucket-handle tear of the complete type lateral discoid meniscus. Both patients received arthroscopic saucerization and repair. A full knee extension under a long leg cast was applied for one month after surgery. The two patients were able to achieve a full range of motion of their operated knees without limping or presenting an antalgic gait at the third month after surgery. Both patients and their parents felt satisfied with the treatment at the 2- and 3-year follow-ups, respectively. Our results demonstrated that arthroscopic saucerization and repair seems to be an effective treatment for bucket-handle tears of the lateral discoid meniscus in young children—even those younger than 3 years old. We reported the youngest case (a 28-month-old girl) in comparison with the findings from a literature review.

Discoid medial meniscus of both knees: A case report

BACKGROUND

Discoid meniscus is a congenital anomaly that typically affects the lateral meniscus. The appearance of the discoid medial meniscus in both knees is extremely rare, with an incidence of only 0.012%.

CASE SUMMARY

Our patient was a 30-year-old female. Under no obvious predisposing causes, she began to experience pain in both knees, which worsened while walking and squatting. The pain was aggravated after exercise, and joint flexion and extension activities were accompanied by knee snapping. Apley’s test was positive on physical examination, and there was a pressing pain in the medial articular space. Plain radiographs of both knees revealed no obvious abnormalities in the bilateral knee joint space. Partial meniscectomy as well as menisci reformation were performed on both knees under arthroscopy. Under the guidance of rehabilitation, the patient’s range of motion in both knees returned to normal without pain and knee snapping.

CONCLUSION

This study showed that the clinical manifestations of the discoid medial meniscus injury are identical to those of the conventional medial meniscus injury, and arthroscopic surgery is effective.

Update on imaging of the discoid meniscus

Discoid menisci represent a range of morphological meniscal variants, most commonly involving the lateral meniscus. Clinical presentation ranges from an asymptomatic incidental finding to snapping, pain, swelling and reduced range of knee movement. Symptomatic presentation of discoid menisci is usually due to meniscal tears and instability resulting from abnormal meniscal morphology and ultrastructure, with absent peri-meniscal ligamentous and meniscocapsular attachments characteristic of the Wrisberg sub-type. This article reviews the current classification systems of discoid menisci, gross morphological characteristics of each sub-type and ultrastructure. Clinical presentation, arthroscopic findings and indirect radiological diagnostic criteria are described, as are the MRI findings of normal and pathological discoid menisci. Current concepts of surgical management and outcomes of the discoid meniscus are also briefly discussed.

Anatomical knee variables result in worse outcomes of lateral meniscal allograft transplantation with discoid lateral menisci than with nondiscoid lateral menisci

PURPOSE

To compare the clinical results of meniscal allograft transplantation (MAT) between patients with discoid lateral meniscus (DLM) and non-DLM (NDLM) and to analyse whether anatomical deformities cause worse clinical results in DLM patients.

METHODS

Patients who underwent unilateral MAT from 2005 to 2017, including 115 patients with DLMs or NDLMs, were included in this study. Clinical outcomes [International Knee Documentation Committee (IKDC) scores, Lysholm scores, Tegner scores, and visual analogue scale (VAS) scores] and radiographic and MRI data were assessed. Clinical outcomes and anatomical knee variables were analysed by multivariate stepwise regression.

RESULTS

After more than 2 years of follow-up, 9 patients were lost to follow-up, and 59 patients with DLM and 47 patients with NDLM were included. The mean postoperative results were significantly better than the preoperative data (P < 0.05) in both the DLM and NDLM groups. In addition, postoperative IKDC, Lysholm, and VAS scores but not Tegner scores were better in the NDLM group than in the DLM group. Several anatomical knee variables differed significantly between the NDLM and DLM groups and were associated with MAT outcomes. The condylar prominence ratio of the lateral and medial femoral condyles adjacent to the intercondylar notch and squaring of the lateral femoral condyle (the distance of the straight articular condylar surface) were independent factors significantly correlated with the Lysholm scores for MAT at last follow-up.

CONCLUSION

MAT improved knee function in both patients with DLM and patients with NDLM, but patients NDLM had better clinical outcomes than patients with DLM. The condylar prominence ratio and squaring of the lateral femoral condyle may underlie this result.

LEVEL OF EVIDENCE

III.

Narrative Review - Knee Pain in the Pediatric Athlete

PURPOSE OF REVIEW

This review article seeks to highlight common youth athlete knee conditions due to overuse or trauma and elucidate differences from the adult populations.

RECENT FINDINGS

Overuse conditions presented include apophysitis, osteochondritis dissecans plica syndrome, and discoid meniscus. Traumatic conditions presented include patellar instability, patellar sleeve fracture, and patellofemoral osteochondral fractures. Knee injuries affect a significant proportion of youth athletes. These injuries place athletes at higher risk of chronic pain and potentially osteoarthritis. We have reviewed common overuse and traumatic knee injuries and differentiating factors between the adult population to improve and expedite the diagnosis, treatment, and prognosis for youth athletes with knee injuries.

Multivariate ordered logistic regression analysis of the postoperative effect of symptomatic discoid lateral meniscus

INTRODUCTION

The postoperative effect of arthroscopy in the treatment of symptomatic discoid lateral meniscus (DLM) varies greatly among individuals. Therefore, this study aims to investigate the factors affecting the postoperative outcomes of symptomatic DLM.

MATERIALS AND METHODS

According to the inclusion and exclusion criteria, patients with symptomatic single-knee DLM who underwent arthroscopic surgery at our hospital from 9/2008 to 9/2015 were included. Retrospectively collected 16 factors probably affecting postoperative outcomes. The Ikeuchi grade system was used to evaluate the knee joint function. Univariate analysis was performed by Kruskal-Wallis rank-sum test or Mann-Whitney U test, and multivariate analysis by ordered logistic regression. P < 0.05 was considered statistically significant.

RESULTS

A sum of 502 patients was included, including 353 females (70.3%) and 149 males (29.7%). Difference between preoperative and postoperative Ikeuchi grade was statistically significant (P < 0.001). Female was bad to obtain a good Ikeuchi grade (P = 0.009, OR 0.458). Outerbridge grade (P = 0.018, OR 0.638) was negatively correlated with Ikeuchi grade. BMI (P = 0.001, OR 0.875) and work intensity (P = 0.020, OR 0.611) were inversely correlated with Ikeuchi grade. Age of onset (P < 0.001, OR 0.956) and symptoms duration (P < 0.001, OR 0.988) were negatively correlated with Ikeuchi grade. Besides, compared to total meniscectomy, meniscoplasty with a repair was an unfavourable factor for Ikeuchi grade (P = 0.044, OR 0.245).

CONCLUSIONS

With the increase of BMI, work intensity, age of onset, duration of symptoms, and the severity of cartilage lesion, the postoperative results become worse. Moreover, female and meniscoplasty with repair are risk factors for the postoperative outcomes.