Discoid Meniscus

Generating New Meniscus Therapies via Recent Breakthroughs in Development, Model Systems, and Clinical Diagnostics

Over 850,000 surgeries are performed to treat meniscal injuries each year in the United States. Even with repair, patients are likely to develop osteoarthritis (OA) within the next two decades. There is a pressing clinical need to improve meniscal repair procedures to restore tissue function and prevent joint degeneration later in life. Here we present a review of recently published articles (2020-2024) spanning basic science, translational, and clinical studies to highlight new advances in meniscus research across development, animal models, finite element models, and clinical interventions. Key progenitor cell populations and vascularity changes have been identified in human meniscus tissue development, aging, and degeneration with implications for novel tissue repair strategies. The use of animal and finite element models has expanded our understanding of meniscus tissue function and evaluated new therapies in preclinical studies. Further, advances in clinical diagnostics with machine learning models and surgical techniques have shed light on evidence-based practices for improving patient outcomes. We discuss across multiple length scales (micro-, meso-, macro-) the structure-function relationship of the meniscus in development and disease, recent advances in models and tools to study the meniscus, knowledge gaps in the field, persisting challenges in clinical treatments and assessments, and the translation of basic science therapies into the clinic.

Pediatric Medial Discoid Meniscus: Case Series and Postoperative Outcomes

Discoid medial meniscus (DMM) is a rare congenital anomaly, with bilateral cases being even more uncommon. Due to its rarity, comprehensive data on its prevalence, clinical presentation, and optimal management strategies are limited. This study aimed to evaluate the prevalence, clinical characteristics, and treatment outcomes of symptomatic DMM in a pediatric population. A retrospective review was conducted on patients under 18 years of age diagnosed with symptomatic DMM. Data were extracted using ICD-10 codes Q68.6 and M23.16 and were supplemented by free-text searches. The inclusion criteria encompassed a confirmed DMM diagnosis, availability of MRI and radiographic imaging, complete clinical documentation, and a minimum of six months of postoperative follow-up. Demographic data, clinical presentations, imaging findings, surgical interventions, and outcomes were analyzed. Three patients (five knees) met the inclusion criteria. All presented with symptomatic DMM requiring surgical intervention. Arthroscopic saucerization combined with meniscal repair was performed in all cases. Postoperative follow-up revealed that two of the patients achieved excellent outcomes, while one required three reoperations due to retearing but remained symptom-free at one year post-revision. Radiographic assessments did not reveal characteristic changes typically associated with DMM. Symptomatic DMM, though rare, may be encountered more frequently than previously reported, especially when focusing on symptomatic cases. Arthroscopic saucerization with concurrent meniscal repair appears to be an effective treatment modality, yielding favorable mid-term outcomes. Given the limited number of cases and the variability in their presentations, further research with larger cohorts is essential to establish standardized management protocols and to better understand the long-term prognosis of patients with this rare condition.

Pediatric Meniscal Tears

As pediatric youth sports involvement has increased, there has been an increase in meniscus tears associated with acute pediatric knee injuries. The meniscus of pediatric patients has a more robust blood supply which may help its healing potential. The discoid meniscus is an anatomical variant that is more prone to meniscal tears in pediatric patients. Meniscectomy and saucerization are usually the treatment of choice for the complex meniscus tear and the discoid meniscus tear. Meniscus repair should be attempted when at all possible due to the good outcomes associated with meniscus repair and poor results associated with meniscectomy in pediatric patients.

Regeneration of a Discoid Meniscus: A Case Report

CASE

A 4-year-old girl with no relevant medical history presented with left knee swelling. Knee laxity, magnetic resonance imaging findings of anterior cruciate ligament (ACL) deficiency and discoid meniscus, and the chronicity of symptoms prompted arthroscopic ACL reconstruction and meniscal saucerization. Pain and swelling continued, and repeat arthroscopy revealed regeneration of the discoid meniscus at 18-month follow-up.

CONCLUSION

In this unusual case, a discoid lateral meniscus regenerated after saucerization. Regeneration could be attributed to the robust vascularity of the meniscus in pediatric patients. Surgeons should counsel about the risk of recurrence after treatment of discoid meniscus.

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.

Arthroscopic Linear Chain Fixation for the Treatment of Medial Meniscus Posterior Root Tear: A Case Study

BACKGROUND

The repair and reconstruction of medial meniscus posterior root tears (MMPRTs) is an important issue in the field of orthopedic sports medicine. This study reports the first application of arthroscopic linear chain fixation for the treatment of MMPRTs.

CASE PRESENTATION

A 78-year-old female patient presented with a 1.5-month history of right knee pain accompanied by a locked facet joint. The patient underwent surgery with the new linear chain fixation method. In this method, the suture and the loop part of the buckle-strap titanium plate were combined into a linear chain mechanical complex, and the tension of the posterior root stump was gradually increased by pulling on the two attachment lines at the external mouth of the tibial tunnel. The postoperative Lysholm score was 89, and the visual analogue scale score was 0.9, indicating a significant improvement in knee joint function. At the 7-month and 1-year post-surgery follow-up, physical and MRI examinations confirmed satisfactory healing of the MMPRTs.

CONCLUSION

This surgical approach offers several benefits, including a simplified instrumentation setup, preservation of natural anatomical structures, and reliable residual stump fixation. It has the potential for clinical implementation.

Comparative analysis of discoid lateral meniscus size: a distinction between symptomatic and asymptomatic cases

PURPOSE

This study evaluated the differences in meniscal sizes and occupancy between symptomatic and asymptomatic patients diagnosed with discoid lateral meniscus (DLM) using magnetic resonance imaging (MRI) to understand how these variations relate to the presence of symptoms and the patients' age.

METHODS

A retrospective review of 98 patients with DLM was conducted, excluding those with meniscal displacement. Both the width and extrusion of DLM and the percentage of the meniscus to the tibia were measured using mid-coronal and mid-sagittal MRI and compared between symptomatic and asymptomatic DLM groups. The relationships among each parameter, meniscal size, and patient age were evaluated. Symptomatic cases were divided into those with and without horizontal tears on MRI to compare the differences in meniscal morphology.

RESULTS

A total of 92 knees from 74 patients were included. Sixty-one knees required surgical intervention for symptomatic DLM, while 31 were asymptomatic and included the contralateral side of symptomatic knees. The symptomatic group exhibited larger morphological variations than the asymptomatic group. Moreover, the sagittal meniscal ratio reduced with age in the asymptomatic group (r = - 0.54, p = 0.002) but remained constant in the symptomatic group. The symptomatic cases with horizontal tears demonstrated larger meniscal dimensions and smaller posterior capsule distances than those without tears.

CONCLUSION

Symptomatic patients with DLM had larger knee morphological changes than asymptomatic ones. Age affected the meniscal occupancy in the sagittal plane only in asymptomatic patients.

LEVEL OF EVIDENCE

III.

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.

Pediatric meniscus morphology varies with age: a cadaveric study

PURPOSE

In adolescent patients, meniscal tear injury can occur either in isolation (e.g., discoid lateral meniscus tears) or in association with other traumatic injuries including tibial eminence fracture or ACL tear. Damage to meniscal integrity has been shown to increase contact pressure in articular cartilage, increasing risk of early onset osteoarthritis. In symptomatic patients failing conservative management, surgical intervention via meniscus repair or meniscus transplant is indicated. The purpose of this study was to evaluate the radial dimensions of pediatric menisci throughout development. The hypothesis was that the average radial meniscus dimensions will increase as specimen age increases, and mean medial and lateral region measurements will increase at a linear rate.

METHODS

Seventy-eight skeletally immature knee cadaver specimens under age 12 years were included in this study. The meniscal specimens were photographed in the axial view with ruler in the plane of the tibial plateau and analyzed using computer-aided design (CAD) software (Autodesk Fusion 360). Measurements were taken from inner to outer meniscus rims at five 45 degree intervals using the clockface as a reference (12:00, 1:30, 3:00, 4:30, 6:00), and total area of meniscus and tibial plateau was recorded. Generalized linear models were used to evaluate the associations of radial width measurements with age, tibial coverage, and lateral vs. medial meniscus widths.

RESULTS

All radial width measurements increased significantly with specimen age (p ≤ 0.002), and all lateral-medial meniscal widths increased (p < 0.001). The anterior zones of the meniscus were found to increase at the slowest rate compared to other regions. Tibial plateau coverage was found to not significantly vary with age.

CONCLUSIONS

Meniscus radial width and lateral-medial meniscus width are related to age. The anterior width of the meniscus varied least with age. Improved anatomic understanding may help surgeons more effectively plan for meniscus repair, discoid resection/saucerization/repair, and also support appropriate selection of meniscus allograft for transplantation.

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.