Meniscus Anatomy and Basic Science

Abnormal lateral meniscal signal in MRI after patellar dislocation does not indicate a meniscal tear: MR findings with surgical correlation

Background

Combined injuries observed with first-time lateral patellar dislocation (LPD) of the knee, particularly significant soft tissue injury, can inform surgical intervention criteria.

Purpose

The purpose of this study was to compare MRI findings in LPD to surgical correlation concerning meniscal pathology as a guide for surgical management.

Study design

Retrospective case series, Level of evidence, 4.

Methods

A retrospective review was conducted of 355 cases of patients with lateral patellar dislocation from 2012 to 2022. Imaging was reviewed by musculoskeletal radiologists blinded to surgical results for evidence of soft tissue injury, and associated arthroscopic data and operative reports were reviewed.

Results

Out of 44 cases of LPD in 42 patients who underwent MPFL reconstructive surgery, 27 (61%) cases had grade 2a or higher signal changes in the anterior horn of the lateral meniscus, of which 10 (23%) had grade 3 signal changes. There were zero cases of meniscal tear in these cases upon review of operative reports and arthroscopic images.

Conclusion

MRI findings of signal alterations in the lateral meniscus post-LPD may not indicate an actual tear. This could aid in surgical decision-making in primary LPD management.

Ramp-like lateral meniscus tear. Description of an infrequent lesion

Numerous studies on meniscal tears have been published, a pathology that continues to evolve in terms of treatment and patient outcomes. As our understanding of anatomy and biomechanics improves, new entities have emerged. The lateral meniscus, especially its posterior attachment, tends to be overlooked due to its greater mobility compared to the medial meniscus. Evaluating the instability of the posterior horn poses a challenge, even during arthroscopy, therefore, it is crucial to understand the posterior menisco-synovial detachment lesions, which are indeed real and, to date, haven't received enough attention in the existing literature. The aim is to describe a new entity affecting the posterior synovial attachment of the lateral meniscus, without injury to the posterior horn of the lateral meniscus (PHLM). We also aim to present a case report detailing the intraoperative diagnosis and management of a 20-year-old patient with a sports trauma that led to a combined anterior cruciate ligament (ACL) and lateral meniscus tear managed with arthroscopic ACL reconstruction and all-inside meniscal suture. Through conventional arthroscopic evaluation of the posterior capsule anatomy and dissections, we have identified a distinct lesion of the PHLM at the menisco-synovial junction. Further research is necessary in this field to understand the biomechanical repercussions and determine the ideal surgical management.

Advances in meniscus tissue engineering: Towards bridging the gaps from bench to bedside

Meniscus is vital for maintaining the anatomical and functional integrity of knee. Injuries to meniscus, commonly caused by trauma or degenerative processes, can result in knee joint dysfunction and secondary osteoarthritis, while current conservative and surgical interventions for meniscus injuries bear suboptimal outcomes. In the past decade, there has been a significant focus on advancing meniscus tissue engineering, encompassing isolated scaffold strategies, biological augmentation, physical stimulus, and meniscus organoids, to improve the prognosis of meniscus injuries. Despite noteworthy promising preclinical results, translational gaps and inconsistencies in the therapeutic efficiency between preclinical and clinical studies exist. This review comprehensively outlines the developments in meniscus tissue engineering over the past decade (Scheme 1). Reasons for the discordant results between preclinical and clinical trials, as well as potential strategies to expedite the translation of bench-to-bedside approaches are analyzed and discussed.

Body mass index and meniscal tears: Evidence from meta-analysis of observational studies and Mendelian randomization

Obesity is a potential risk factor for meniscal tear (MT). We utilized meta-analysis of observational studies and Mendelian randomization (MR) analyses to elucidate the association between body mass index (BMI) and MT. In meta-analysis, a search was performed on June 27, 2022, using PubMed and Embase databases. Odds ratios and 95% confidence intervals were extracted from included studies. In MR analyses, the research utilized summary-level data on BMI and MT obtained from Genetic Investigation of Anthropometric Traits and the FinnGen Consortium, respectively. In meta-analysis, four studies comprising 826,383 participants were included. The pooled odds ratio of MT in the high BMI group was 1.32 (95% confidence interval, 0.83-2.09), compared with the nonhigh BMI group. The pooled odds ratio in the under 30 group was 1.76 (95% confidence interval, 0.61-5.03). In MR analyses, one standard deviation increase in genetically predicted BMI was associated with meniscus derangement as a chronic subtype of MT (odds ratio, 1.36; 95% confidential interval, 1.17-1.59). We found that a high BMI was not associated with an increased likelihood of MT based on meta-analysis of observational studies; however, by complementing MR analyses, we elucidated the causality of BMI increase on meniscus derangement as a chronic subtype of MT.

Alteration of knee joint moment after anterior cruciate ligament reconstruction conditions in subjects with and without meniscal pathology

BACKGROUND

The effects of anterior cruciate ligament (ACL) reconstruction on postoperative gait biomechanics remain controversial, and the influence of meniscus pathology on pre- and post-ACL reconstruction biomechanical changes has not yet been studied. Here, we aimed to clarify the difference in knee joint moment between pre- and post-ACL reconstruction conditions in subjects with and without meniscal pathology.

METHODS

Twenty-four subjects with unilateral ACL reconstruction injuries participated in this study. A total of 13 of the subjects had concomitant meniscus injuries. Gait analysis was performed preoperatively and at 11 months postoperatively. Three-dimensional knee joint angles and moments were calculated based on motion-capture data. The total joint moment and contribution of individual moments during the stance phase were assessed. For statistical analysis, we compared pre- and postoperative alterations, and differences were assessed in subjects with and without meniscal pathology.

RESULTS

Tibial rotation excursion was lower in subjects with meniscal pathology than in those with intact menisci postoperatively. An significant increase in the contribution of the knee flexion moment and a significant decrease in the contribution of the knee adduction moment postoperatively were observed in subjects with intact menisci.

CONCLUSIONS

Patients with ACL injury showed different postoperative alterations in joint moments depending on the concomitant meniscal injury.

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.

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.

Advances in Hydrogels for Meniscus Tissue Engineering: A Focus on Biomaterials, Crosslinking, Therapeutic Additives

Meniscus tissue engineering (MTE) has emerged as a promising strategy for meniscus repair and regeneration. As versatile platforms, hydrogels have gained significant attention in this field, as they possess tunable properties that allow them to mimic native extracellular matrices and provide a suitable microenvironment. Additionally, hydrogels can be minimally invasively injected and can be adjusted to match the shape of the implant site. They can conveniently and effectively deliver bioactive additives and demonstrate good compatibility with other functional materials. These inherent qualities have made hydrogel a promising candidate for therapeutic approaches in meniscus repair and regeneration. This article provides a comprehensive review of the advancements made in the research on hydrogel application for meniscus tissue engineering. Firstly, the biomaterials and crosslinking strategies used in the formation of hydrogels are summarized and analyzed. Subsequently, the role of therapeutic additives, including cells, growth factors, and other active products, in facilitating meniscus repair and regeneration is thoroughly discussed. Furthermore, we summarize the key issues for designing hydrogels used in MTE. Finally, we conclude with the current challenges encountered by hydrogel applications and suggest potential solutions for addressing these challenges in the field of MTE. We hope this review provides a resource for researchers and practitioners interested in this field, thereby facilitating the exploration of new design possibilities.

Short-term transplantation effect of a tissue-engineered meniscus constructed using drilled allogeneic acellular meniscus and BMSCs

During the construction of tissue-engineered meniscus, the low porosity of extracellular matrix restricts the flow of nutrient solution and the migration and proliferation of cells, thus affecting the tissue remodeling after transplantation. In this study, the canine allogeneic meniscus was drilled first and then decellularized. The drilled tissue-engineered menisci (Drilled Allogeneic Acellular Meniscus + Bone Marrow Mesenchymal Stem Cells, BMSCs) were transplanted into the knee joints of model dogs. On the basis of ensuring the mechanical properties, the number of the porosity and the cells implanted in allogeneic acellular meniscus was significantly increased. The expression levels of glycosaminoglycans and type II collagen in the drilled tissue-engineered meniscus were also improved. It was determined that the animals in the experimental group recovered well-compared with those in the control group. The graft surface was covered with new cartilage, the retraction degree was small, and the tissue remodeling was good. The surface wear of the femoral condyle and tibial plateau cartilage was light. The results of this study showed that increasing the porosity of allogeneic meniscus by drilling could not only maintain the mechanical properties of the meniscus and increase the number of implanted cells but also promote cell proliferation and differentiation. After transplantation, the drilled tissue-engineered meniscus provided a good remodeling effect in vivo and played a positive role in repairing meniscal injury, protecting articular cartilage and restoring knee joint function.

The meniscal extrusion index is a reliable indirect sign of different meniscal lesion patterns: a classification based on percentage of meniscal extrusion

PURPOSE

This study's goal is to propose a straightforward classification system based on the MEI (Meniscal Extrusion Index), a measure of meniscal extrusion, that relates to various meniscal lesion patterns and has clinical and biomechanical significance. The study's secondary goal is to determine whether the standard 3 mm meniscal extrusion parameter still has value by correlating the MEI with it.

METHODS

1350 knee MRIs that were performed over the course of 2 years made up the study cohort. Following the application of inclusion and exclusion criteria, 200 of those patients were qualified to participate in the study. All the measurements examined for this study underwent an interobserver reliability test.

RESULTS

In the 1350 MRIs that were examined for this study, meniscal extrusion of any grade was present 18.9% of the time. The use of the MEI revealed three groups of patients: those with a MEI < 20%, who are likely para-physiological; those with a MEY between 20% and 40%, who are in a grey area; and those with a MEY > 40%, who have lesions that are impairing the proper meniscal function. According to the authors' findings, the percentage of meniscal extrusion did not correlate with the finite number (3 mm), making the 3 mm parameter an unreliable evaluation method.

CONCLUSIONS

This study is clinically relevant, because it proposes a simple and reproducible classification of meniscal extrusion that may aid in evaluating the severity of an extrusion and help in the diagnosis of lesions that might be difficult to identify on MRI.

LEVEL OF EVIDENCE

Level IV.

Covariance in human limb joint articular morphology

OBJECTIVES

Limb synovial joints exhibit complex shapes that must accommodate often-antagonistic demands of function, mobility, and stability. These demands presumably dictate coordination among joint articular shapes, but the structure of morphological covariance within and among joints is unknown. This study analyzes the human shoulder, elbow, hip, and knee to determine how articular covariance is structured in relation to joint structure, accessory cartilage, and function.

MATERIALS AND METHODS

Surface models were created from the CT scans of 200 modern skeletons from the University of Tennessee Donated Skeletal Collection. Three-dimensional landmarks were collected on the shoulder, elbow, hip, and knee joints. Two-block partial least squares were conducted to determine associations between surfaces of conarticular shapes, functionally analogous articulations, and articulations belonging to the same bone.

RESULTS

Except for the components of the shoulder, all conarticular pairs exhibit covariance, though the strength of these relationships appears unrelated to the amount of accessory cartilage in the joint. Only the analogous articulations of the humerus and femur exhibit significant covariance, but it is unlikely that this pattern is due to function alone. Stronger covariance within the lower limb than the upper limb is consistent broader primate patterns of within-limb integration.

DISCUSSION

With the exception of the elbow, complementary joint function does not appear to promote strong covariance between articulations. Analogous humeral and femoral surfaces are also serially homologous, which may result in the articular associations observed between these bones. Broadly, these patterns highlight the indirect relationship between joint congruence and covariance.

Tear patterns and locations are different between lateral and medial compartments in patients with early anatomical failure after meniscal allograft transplantation

PURPOSE

To investigate the characteristics of anatomically failed grafts within 1 year after meniscal allograft transplantation (MAT) and compare the differences between lateral and medial MATs.

METHODS

The records of consecutive patients with anatomically failed grafts within 1 year after primary MAT between 2005 and 2018 were reviewed. Anatomical failure was defined as a tear covering > 50% of the allograft or an unstable peripheral rim. The pattern and location of the graft tears were analyzed using magnetic resonance imaging or arthroscopy.

RESULTS

A total of 21 patients were included. All 21 patients had anatomical failure with tears involving > 50% of the allograft, whereas 15 had an unstable peripheral rim of the allograft. The mean failure time was 6.6 ± 3.6 months in all patients (lateral MAT, n = 15; medial MAT, n = 6). In the lateral MAT group, meniscocapsular separation was the most common pattern (n = 10, 66.7%), followed by complex (n = 3, 20.0%), radial (n = 1, 6.7%), and longitudinal (n = 1, 6.7%) tear. In the medial MAT group, a root tear was the most common pattern (n = 5, 83.3%), followed by a complex tear (n = 1, 16.7%). Meanwhile, in the lateral MAT, the midbody was the most frequently affected location (n = 9, 60.0%), followed by the posterior (n = 5, 33.3%) and anterior (n = 1, 6.7%) areas; in the medial MAT group, the posterior (n = 5, 83.3%) was the most frequently affected location, followed by the anterior area (n = 1, 16.7%). Significant differences in the pattern (P = 0.002) and location (P = 0.043) of the graft tears were found between lateral and medial MATs.

CONCLUSION

In patients with early failure after MAT, meniscocapsular separation in the midbody of the lateral compartment and root tears in the posterior area of the medial compartment were the most common. Thus, surgeons are encouraged to pay extra attention to these vulnerable areas during the early period after MAT.

LEVEL OF EVIDENCE

IV.

Securing the Root: Meniscus Root Repair with Rip Stop and Cannulated Drilling

Meniscal root pathology has garnered increased attention over the past decade. Meniscal root tears are considered to essentially represent a meniscus-deficient state, which has led to a rise in the surgical fixation of this pathology. Meniscus root tears are classified as either radial tears within 1 cm of the root insertion, or a direct avulsion of meniscal root. These injuries are important to recognize because they contribute to impaired joint mechanics and rapid articular cartilage degeneration. Given this, there remains significant interest in identifying novel surgical techniques that may facilitate better surgical repair and enhance patient outcomes. The purpose of this technical note is to describe a surgical technique for a medial meniscus root ripstop repair with cannulated drilling. This technique is simple and reproducible, while also allowing for the augmentation of potentially poor tissue quality.

Outside-in repair technique is effective in traumatic tears of the meniscus in active adults: a systematic review

PURPOSE

Meniscal injuries are common. Outside-in meniscal repair is one of the techniques advocated for the management of traumatic meniscal tears. This systematic review investigated the outcomes of the outside-in repair technique for the management of traumatic tears of the menisci. The outcomes of interest were to investigate whether PROMs improved and to evaluate the rate of complications.

METHODS

Following the 2020 PRISMA statement, in May 2023, PubMed, Web of Science, Google Scholar, and Embase were accessed with no time constraints. All the clinical investigations which reported data on meniscal repair using the outside-in technique were considered for inclusion. Only studies which reported data on acute traumatic meniscal tears in adults were considered. Only studies which reported a minimum of 24 months of follow-up were eligible.

RESULTS

Data from 458 patients were extracted. 34% (155 of 458) were women. 65% (297 of 458) of tears involved the medial meniscus. The mean operative time was 52.9 ± 13.6 min. Patients returned to their normal activities at 4.8 ± 0.8 months. At a mean of 67-month follow-up, all PROMs of interest improved: Tegner scale (P = 0.003), Lysholm score (P < 0.0001), International Knee Documentation Committee (P < 0.0001). 5.9% (27 of 458) of repairs were considered failures. Four of 186 (2.2%) patients experienced a re-injury, and 5 of 458 (1.1%) patients required re-operation.

CONCLUSION

Meniscal repair using the outside-in technique can be effectively performed to improve the quality of life and the activity level of patients with acute meniscal tears.

LEVEL OF EVIDENCE

Level IV.

The continuous structure of the joint capsule and meniscus in the pig knee

The knee joint capsules composed of a fibrous layer and a synovial layer. The knee meniscus consists of the superficial network, lamellar layer, tie fibre and circumferential bundles. However, the continuous structure of the knee joint capsule and meniscus has not been reported. Fetal and adult pigs were used to investigate the structural relationship between the stifle joint capsule and meniscus based on the gross anatomy and histological findings. In the gross anatomical examination, the joint capsule appeared to have separated attachments to the meniscus, except for the lower aspect of the popliteal hiatus. Histologically, the lower half of the popliteal hiatus was found to have separated attachments, with vessels running between the attachments of the joint capsules. The synovial layer of the joint capsule continued to the superficial network, and the fibrous layer of the joint capsule continued to the lamellar layer and tie fibres. There were two routes of arterial entry into the meniscus: intracapsular and intercapsular. It appeared that the presence of separated attachments of the joint capsule was necessary to allow the intercapsular route. This study clarified for the first time the routes of feeding vessels entering the meniscus and proposed to call this entry point the meniscus hilum. We consider that this detailed anatomical information is important for understanding the continuation between the joint capsule and the meniscus.

Placement of a polyurethane implant is not associated with a chondroprotective effect: comparative study with cases of isolated medial meniscectomy with at least five years of follow-up

INTRODUCTION

Our main objective was to evaluate clinically and radiologically and compare patients who had undergone partial meniscectomy alone, with those who had received a partial meniscectomy in which a polyurethane implant was placed, with a minimum follow-up of 5 years.

METHODS

We performed a prospective cohort study. Patients were randomly distributed into Group A if they only received meniscectomy or Group B if they received meniscectomy plus a meniscal implant (Actifit®). We performed preoperative, postoperative, and 5-year-follow-up functional and radiological evaluations (magnetic resonance imaging).

RESULTS

Twelve patients (40%) were treated with meniscal implants (Group B); 18 (60%) were treated with a conventional meniscectomy (Group A). Tegner, Lysholm and KOOS scores were evaluated prior to surgery and at 5-year follow-up. Only the Lysholm score showed a significant difference between groups, with a score increase between the preoperative evaluation and the 5-year follow-up evaluation (p = 0.013). Preoperative and postoperative MRIs were both available in 19 cases (63.3%). Long-term follow-up MRIs were performed in 11 cases of group B. No significant differences were found in functional outcomes or MRI findings (WORMS cartilage score increase p = 0.360). Although total reabsorptions of the collagen meniscus implant were not statistically significant in younger patients, a tendency towards a higher reabsorption process was seen in older patients (p = 0.015).

CONCLUSION

The placement of a polyurethane implant after a wide meniscectomy is not accompanied by a chondroprotective effect over time. There is no functional difference between implant placement and isolated meniscectomy. There is a discrepancy between good clinical results and radiologic appearance of these implants and their underlying cartilage.

LEVEL OF EVIDENCE

II, therapeutic study.

Minced Meniscus: Biologic Augmented Meniscal Implant Treatment

Applications of meniscus scaffolds are crucial for preserving articular cartilage tissue, restoring normal joint mechanics, and stabilizing joints with partial meniscus deficits. Studies are still being conducted to determine how meniscus scaffold applications can create viable and durable tissue. The surgical procedure described in this study uses the meniscus scaffold and minced meniscus tissue.

Integrin αVβ3 Signaling in the Progression of Osteoarthritis Induced by Excessive Mechanical Stress

Osteoarthritis (OA) is believed to be linked with cartilage degeneration, subchondral bone sclerosis, and synovial inflammation that lead to joint failure, and yet treatment that can effectively reverse the pathological process of the disease still not exists. Recent evidence suggests excessive mechanical stress (eMS) as an essential role in the pathogenesis of OA. Increased levels of integrin αVβ3 have been detected in osteoarthritic cartilage and were previously implicated in OA pathogenesis. However, the role of integrin αVβ3 in the process of eMS-induced OA remains unclear. Here, histologic and proteomic analyses of osteoarthritic cartilage in a rat destabilization of the medial meniscus model demonstrated elevated expression of integrin αVβ3 as well as more serious cartilage degeneration in the medial weight-bearing area. Furthermore, results of in vitro study demonstrated that eMS led to a significant increase of integrin αVβ3 expression and phosphorylation of downstream signaling molecules such as FAK and ERK, as well as upregulated expressions of inflammatory and degradative mediators. In addition, we found that inhibition of integrin αVβ3 could alleviate chondrocyte inflammation triggered by eMS both in vivo and in vitro. Our findings suggest a central role for upregulation of integrin αVβ3 signaling in OA pathogenesis and demonstrate that activation of integrin αVβ3 signaling in cartilage contributes to inflammation and joint destruction in eMS-induced OA. Taken together, our data presented here provide a possibility for targeting integrin αVβ3 signaling pathway as a disease-modifying therapy.

LTF induces senescence and degeneration in the meniscus via the NF-κB signaling pathway: A study based on integrated bioinformatics analysis and experimental validation

Background: The functional integrity of the meniscus continually decreases with age, leading to meniscal degeneration and gradually developing into osteoarthritis (OA). In this study, we identified diagnostic markers and potential mechanisms of action in aging-related meniscal degeneration through bioinformatics and experimental verification. Methods: Based on the GSE98918 dataset, common differentially expressed genes (co-DEGs) were screened using differential expression analysis and the WGCNA algorithm, and enrichment analyses based on Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were further performed. Next, the co-DEGs were imported into the STRING database and Cytoscape to construct a protein‒protein interaction (PPI) network and further validated by three algorithms in cytoHubba, receiver operating characteristic (ROC) curve analysis and the external GSE45233 dataset. Moreover, the diagnostic marker lactotransferrin (LTF) was verified in rat models of senescence and replicative cellular senescence via RT‒qPCR, WB, immunohistochemistry and immunofluorescence, and then the potential molecular mechanism was explored by loss of function and overexpression of LTF. Results: According to the analysis of the GSE98918 dataset, we identified 52 co-DEGs (42 upregulated genes and 10 downregulated genes) in the OA meniscus. LTF, screened out by Cytoscape, ROC curve analysis in the GSE98918 dataset and another external GSE45233 dataset, might have good predictive power in meniscal degeneration. Our experimental results showed that LTF expression was statistically increased in the meniscal tissue of aged rats (24 months) and senescent passage 5th (P5) meniscal cells. In P5 meniscal cells, LTF knockdown inhibited the NF-κB signaling pathway and alleviated senescence. LTF overexpression in passage 0 (P0) meniscal cells increased the expression of senescence-associated secretory phenotype (SASP) and induced senescence by activating the NF-κB signaling pathway. However, the senescence phenomenon caused by LTF overexpression could be reversed by the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). Conclusion: For the first time, we found that increased expression of LTF was observed in the aging meniscus and could induce meniscal senescence and degeneration by activating the NF-κB signaling pathway. These results revealed that LTF could be a potential diagnostic marker and therapeutic target for age-related meniscal degeneration.

Intra-Articular Mesenchymal Stem Cell Injection for Knee Osteoarthritis: Mechanisms and Clinical Evidence

Knee osteoarthritis presents higher incidences than other joints, with increased prevalence during aging. It is a progressive process and may eventually lead to disability. Mesenchymal stem cells (MSCs) are expected to repair damaged issues due to trilineage potential, trophic effects, and immunomodulatory properties of MSCs. Intra-articular MSC injection was reported to treat knee osteoarthritis in many studies. This review focuses on several issues of intra-articular MSC injection for knee osteoarthritis, including doses of MSCs applied for injection and the possibility of cartilage regeneration following MSC injection. Intra-articular MSC injection induced hyaline-like cartilage regeneration, which could be seen by arthroscopy in several studies. Additionally, anatomical, biomechanical, and biochemical changes during aging and other causes participate in the development of knee osteoarthritis. Conversely, appropriate intervention based on these anatomical, biomechanical, biochemical, and functional properties and their interactions may postpone the progress of knee OA and facilitate cartilage repair induced by MSC injection. Hence, post-injection rehabilitation programs and related mechanisms are discussed.

Management Strategies and Imaging Observation of Early and Delayed Intelligent Treatment of Meniscus Sports Injury under Knee Osteoarthroscopy

Objective

To investigate the meniscus characteristics of knee osteoarthritis and its guiding significance for minimally invasive surgery.

Methods

A total of 100 patients with knee meniscus sports injuries who were treated in our hospital from January 2019 to January 2022 were selected as the research subjects and were grouped according to the interval between injury and surgery, with an interval of 2 months: the early group (53 cases) within 2 months and the delayed group (47 cases) with an interval of more than 2 months. The distribution of intraoperative complications in the two groups was observed and recorded, and the changes in pain degree, joint range of motion, knee joint function, and quality of life scores before and after operation were compared between the two groups.

Results

The postoperative VAS score, range of motion, Lysholm score, IKDC knee subjective function score, and quality of life score were significantly improved in both groups (P < 0.05). The incidence of intra-articular cartilage injury in the delayed group was significantly higher than that in the early group (P < 0.05). The patellofemoral cartilage injury was the main part of intra-articular cartilage injury in the two groups, and the incidence of patellofemoral cartilage injury in the delayed group was significantly higher than that in the early group (P < 0.05). The cartilage damage was mainly cartilage damage, and the grades I-II and III-IV cartilage damages were significantly increased in the extension group.

Conclusion

Meniscal injury in knee osteoarthritis has certain microscopic characteristics. In this paper, the microscopic classification of meniscus injury in knee osteoarthritis is helpful to guide microscopic surgery and improve the minimally invasive knee osteoarthritis effect of surgical treatment.

Review of Meniscus Anatomy and Biomechanics

PURPOSE OF REVIEW

Anatomic repair of meniscal pathology is critical for restoring native joint biomechanics and kinematics for patients who suffer from meniscal tears. The purpose of this review was to summarize the pertinent anatomy, biomechanics, and kinematics of the meniscus to guide surgeons during meniscal repair procedures.

RECENT FINDINGS

Over the past decade, there has been a growing trend to save the meniscus whenever possible. The goal of repair should be to recreate native anatomy as close as possible to recapitulate normal mechanics. Studies describing the quantitative and qualitative relationship of the meniscus roots, ligaments, and attachments are key in guiding any meniscus repair. This review summarizes these relationships, with particular emphasis on meniscal roots and other key attachments to the meniscus. The composition, embryology, vascularization, biomechanics, in vivo kinetics, and in vivo kinematics of the meniscus are also discussed in this review. Meniscal tears can cause profound functional, biomechanical, and kinematic derangements within the knee joint leading to accelerated degeneration of the articular cartilage. A strong understanding of the quantitative and qualitative relationships of the meniscus and its attachments with key arthroscopic landmarks will allow a surgeon to anatomically repair meniscal pathology in order to restore native joint biomechanics.

Meniscus repair: up-to-date advances in stem cell-based therapy

The meniscus is a semilunar fibrocartilage between the tibia and femur that is essential for the structural and functional integrity of the keen joint. In addition to pain and knee joint dysfunction, meniscus injuries can also lead to degenerative changes of the knee joint such as osteoarthritis, which further affect patient productivity and quality of life. However, with intrinsic avascular property, the tearing meniscus tends to be nonunion and the augmentation of post-injury meniscus repair has long time been a challenge. Stem cell-based therapy with potent regenerative properties has recently attracted much attention in repairing meniscus injuries, among which mesenchymal stem cells were most explored for their easy availability, trilineage differentiation potential, and immunomodulatory properties. Here, we summarize the advances and achievements in stem cell-based therapy for meniscus repair in the last 5 years. We also highlight the obstacles before their successful clinical translation and propose some perspectives for stem cell-based therapy in meniscus repair.

Meniscus Matrix Structural and Biomechanical Evaluation: Age-Dependent Properties in a Swine Model

The analysis of the morphological, structural, biochemical, and mechanical changes of the Extracellular Matrix (ECM), which occur during meniscus development, represents the goal of the present study. Medial fully developed menisci (FD, 9-month-old pigs), partially developed menisci (PD, 1-month-old piglets), and not developed menisci (ND, from stillbirths) were collected. Cellularity and glycosaminoglycans (GAGs) deposition were evaluated by ELISA, while Collagen 1 and aggrecan were investigated by immunohistochemistry and Western blot analyses in order to be compared to the biomechanical properties of traction and compression tensile forces, respectively. Cellularity decreased from ND to FD and GAGs showed the opposite trend (p < 0.01 both). Collagen 1 decreased from ND to FD, as well as the ability to resist to tensile traction forces (p < 0.01), while aggrecan showed the opposite trend, in accordance with the biomechanics: compression test showed that FD meniscus greatly resists to deformation (p < 0.01). This study demonstrated that in swine meniscus, clear morphological and biomechanical changes follow the meniscal maturation and specialization during growth, starting with an immature pattern (ND) to the mature organized meniscus of the FD, and they could be useful to understand the behavior of this structure in the light of its tissue bioengineering.