Is intra-articular pathology associated with MCL edema on MR imaging of the non-traumatic knee?

Meniscal Extrusion Measurements After Posterior Medial Meniscus Root Tears: A Systematic Review and Meta-analysis

BACKGROUND

Meniscal extrusion has become increasingly utilized when evaluating meniscus root abnormalities. However, no consensus definition or approach exists on how to measure extrusion.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate the extent of heterogeneity in meniscal extrusion measurement techniques and reported extrusion values in knees with posterior medial meniscus root tears (PMMRTs). We hypothesized that meniscal extrusion measurement techniques would vary considerably throughout reported studies, with resultant wide-ranging published extrusion values.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The inclusion criteria consisted of all clinical and cadaveric studies reporting on meniscal extrusion after PMMRTs, excluding studies lacking data in full extension, those presenting only semiquantitative analyses, articles reporting only differences in meniscal extrusion, and review articles.

RESULTS

A total of 45 studies were included. Imaging modality types included magnetic resonance imaging (89%), 3-dimensional reconstruction with computed tomography (7%), linear displacement transducers (2%), and a combination of magnetic resonance imaging and ultrasound (2%). The 3 most commonly used landmarks to acquire coronal images for meniscal extrusion measurements were the medial collateral ligament (38%), the midpoint of the anterior-posterior length of the medial meniscus (23%), and the middle of the medial femoral condyle (19%). The pooled mean extrusion values according to the measurement location were 3.5 ± 0.7 mm, 3.9 ± 0.8 mm, and 4.5 ± 2.1 mm, respectively, with no significant differences noted between the modality types (P = .23). The pooled mean meniscal extrusion from all included studies was 3.2 ± 2.0 mm.

CONCLUSION

Substantial variation exists in measurement techniques for meniscal extrusion, particularly as it relates to the coronal cross-sectional reference location. Further studies should aim to provide clear descriptions of the measurement method and have uniform measurement methodology to allow comparisons and pooling between studies.

Evaluation of Medial Meniscal Extrusion Using Radiography

Recently, there has been increasing interest in medial meniscal extrusion (MME), but few reports have evaluated MME via X-ray. In this study, the amount of MME and meniscal height at the medial border of the tibia were measured via X-ray with gradation processing. The extrusion length divided by the meniscal height yields the meniscal extrusion ratio, which was used as an index. In addition, the medial meniscal length of the part protruding from the medial border of the tibia on MRI was measured as an absolute value. Then, the correlation between the meniscal extrusion ratio and the amount of MME on MRI was examined, and there was a strong correlation between the meniscal extrusion ratio via X-ray and the amount of MME on MRI (correlation coefficient 0.860, p < 0.0001). The cut-off value of the meniscal extrusion ratio via X-ray for positive meniscal extrusion on MRI was 0.50, with an AUC of 0.9825, sensitivity of 0.9063, and specificity of 0.8663. From the present study, it was possible to measure the extrusion length and meniscal height via gradation processing, with X-ray and without MRI, and to calculate the meniscal extrusion ratio, which strongly correlates with the amount of MME on MRI.

Morphological changes in the superficial medial collateral ligament on knee MR imaging: association with medial meniscal extrusion and posterior root medial meniscus abnormality

OBJECTIVE

To assess the association between morphological changes in the superficial medial collateral ligament and meniscal extrusion with medial meniscus posterior root tear.

MATERIALS AND METHODS

From January 1, 2018, to December 31, 2019, 124 patients who underwent knee MRI within 90 days prior to knee surgery and whose medial meniscus surgically proved intact, with posterior root tear or posterior horn tear, were enrolled. Two radiologists who were blinded to the surgical results assessed the morphological changes in the superficial medial collateral ligament, including thickness, bowing angle, and presence of signal intensity alteration, and medial meniscus extrusion, according to the presence of tears in the posterior root of the medial meniscus or posterior horn of the medial meniscus using the chi-square test, one-way ANOVA, and Cohen's kappa test.

RESULTS

Thirty-six posterior root tears, 31 posterior horn tears, and 57 intact medial menisci were observed surgically. The mean values of thickness showed no significant differences among the three groups. The bowing angle was significantly higher in the posterior root tear than in the posterior horn tear (reader 1 = 0.001, reader 2 = 0.002) and normal meniscus groups (readers 1 and 2 < 0.001). The percentage of superficial medial collateral ligament signal intensity alteration and meniscal extrusion was highest in the group with posterior root of the medial meniscus tear (80.6% and 94.4%, respectively) and lowest in the group with normal medial meniscus (17.5% and 10.5%, respectively).

CONCLUSION

Morphological changes in the superficial medial collateral ligament and meniscal extrusion were associated with medial meniscus posterior root tears.

Meniscal Extrusion: A Narrative Review

Background:

Meniscal extrusion, referred to as an external displacement of the meniscus, is a commonly encountered but often overlooked magnetic resonance imaging finding in the knee joint. Meniscal extrusion alters the biomechanical properties of the meniscus, leading to accelerated cartilage degeneration and early osteoarthritic changes. The literature contains discrepancies about meniscal extrusion on topics ranging from definition to diagnosis. This narrative review outlines the pathogenesis, natural history, diagnosis, and treatment of meniscal extrusion.

Purpose:

To review the current literature on meniscal extrusion, from pathogenesis to treatment, and to provide recommendations for future research.

Study Design:

Narrative review.

Methods:

A computer-based search of the PubMed, Ovid Medline, and Cochrane Library databases was used to perform a comprehensive literature review on meniscal extrusion. A total of 81 studies was ultimately included in the review.

Results:

The literature review highlighted the current ambiguity in definition, difficulty in clinical diagnosis, and low level of awareness of this condition. This review covers all aspects related to meniscal extrusion and identifies many of its lesser known aspects.

Conclusion:

In the current literature, meniscal extrusion remains a lesser known albeit common condition because of its relatively silent nature along with lack of knowledge among orthopaedic surgeons. Further studies are warranted to provide better understanding and management of this condition.

Stress radiography findings in medial meniscus posterior root tears

BACKGROUND

The present study aimed to evaluate stress radiography and magnetic resonance imaging (MRI) findings in medial meniscus posterior root tears (MMPRTs).

METHODS

The study included 27 patients (26 females, mean age, 53.52 years) who underwent high tibial osteotomy and in whom medial menisci were concurrently examined arthroscopically. Preoperative stress radiographs and MRI series in 14 cases with root tears (MMPRT group, detected arthroscopically) and in 13 cases without tears (control group) were evaluated. Joint spaces measured on the stress radiographs were compared between the operated and opposite knees in each group.

RESULTS

On the varus stress radiographs, the mean lateral joint space of the operated knees was significantly wider than that of the opposite knees in the MMPRT group (P = 0.007). Upon MRI studies, meniscal extrusion was significantly more common in the MMPRT group than in the control group. Moreover, the amount of meniscal extrusion was correlated with the tear size.

CONCLUSIONS

Widening of the lateral joint space on the varus stress radiography was higher in the cases with root tears. Therefore, we propose that stress radiographs can be helpful in the diagnosis of MMPRT.

Association of Medial Meniscus Extrusion With the Prominence of a Fascicular Capsulofemoral Band Subjacent to the Deep Medial Collateral Ligament

OBJECTIVE

The objective of our study was to test our hypothesis that a transverse oblique fascicular anteromedial capsulofemoral band partially subjacent to the deep medial collateral ligament (MCL) is more prominent in knees with medial meniscal extrusion.

MATERIALS AND METHODS

We retrospectively analyzed all knee MRI examinations from a 6-month period for the presence and dimensions of the anteromedial capsulofemoral band on coronal proton-density fat-saturated images and also for medial meniscus extrusion, which was defined as extrusion of 3 mm or greater. Edemalike signal intensity within or in the vicinity of the anteromedial capsulofemoral band, partial or complete tears of the MCL, a history of MCL surgery, or a neoplastic mass lesion violating the medial supporting structures were exclusion criteria. We reviewed procedural videos of patients who subsequently underwent knee arthroscopy. MRI of a cadaveric knee was performed and was followed by dissection and histologic examination.

RESULTS

MRI examinations of 346 knees of 312 patients met the inclusion criteria; of these knees, 50 had medial meniscus extrusion. The anteromedial capsulofemoral band was discernible on MRI in all knees except five (98.6%), and it was visible in six of the arthroscopy videos of 17 knees. The anteromedial capsulofemoral band was thicker on MRI of patients with medial meniscus extrusion (p < 0.0001). The anteromedial capsulofemoral band was identified on MRI and at dissection of the cadaveric knee, and histologic examination revealed that the anteromedial capsulofemoral band was a capsuloligamentous structure.

CONCLUSION

A transverse oblique anteromedial capsulofemoral band subjacent to the deep MCL is thicker in knees with medial meniscus extrusion.

The Knee

Sports injuries at the knee are very common, not only in contact sports such as football but also in sports with jumping and pivoting. In addition, overuse injuries can affect the tendons, ligaments, and bone with degeneration, friction, and stress response. Radiologists and sports medicine professionals should be familiar with the range of injury occurring at the knee and patterns of injury that can be used to predict other more subtle pathology. These topics and others will be discussed.

Response of knee fibrocartilage to joint destabilization

OBJECTIVE

A major challenge to understanding osteoarthritis (OA) pathology is identifying the cellular events that precede the onset of cartilage damage. The objective of this study is to determine the effect of joint destabilization on early changes to fibrocartilage in the joint.

DESIGN/METHODS

The anterior cruciate ligament was transected in collagen reporter mice (Col1CFP and ColXRFP). Mineralization labels were given every 2 weeks to measure new mineralized cartilage apposition. Novel fluorescent histology of mineralized tissue was used to characterize the changes in fibrocartilage at 2 and 4 weeks post-injury.

RESULTS

Changes in fibrocartilaginous structures of the joint occur as early as 2 weeks after injury and are well developed by 4 weeks. The alterations are seen in multiple entheses and in the medial surface of the femoral and tibial condyles. In the responding entheses, mineral apposition towards the ligament midsubstance results in thickening of the mineralize fibrocartilage. These changes are associated with increases in ColX-RFP, Col1-CFP reporter activity and alkaline phosphatase enzyme activity. Mineral apposition also occurs in the fibrocartilage of the non-articular regions of the medial condyles by 2 weeks and develops into osteophytes by 4 weeks post-injury. An unexpected observation is punctate expression of tartrate resistant acid phosphatase activity in unmineralized fibrochondrocytes adjacent to active appositional mineralization.

DISCUSSION

These observations suggest that fibrocartilage activates prior to degradation of the articular cartilage. Thus clinical and histological imaging of fibrocartilage may be an earlier indicator of disease initiation and may indicate a more appropriate time to start preventative treatment.

Risk factors for medial meniscal pathology on knee MRI in older US adults: a multicentre prospective cohort study

OBJECTIVES

Meniscal pathology in which the aetiology is often unclear is a frequent finding on knee MRI. This study investigates potential risk factors for medial meniscal lesions or extrusion in middle-aged and elderly persons.

METHODS

Prospective cohort study using population-based subjects from Birmingham, Alabama and Iowa City, Iowa, USA (the Multicenter Osteoarthritis Study). 644 men and women aged 50-79 years with or at high risk of knee osteoarthritis (Kellgren and Lawrence grade 0-2) but with normal medial meniscal status at baseline were studied. Paired baseline and 30-month 1.0 T knee MRI were scored for meniscal lesions and extrusion (pathology) and the following systemic, knee-specific and compartment-specific potential risk factors were evaluated: age, sex, body mass index, bony enlargement of finger joints, knee trauma, leg-length inequality and knee alignment.

RESULTS

Of 791 knees, 77 (9.7%) had medial meniscal pathology at 30 months follow-up. 61 of the 77 (81%) had no report of trauma during follow-up. Including all potential risk factors in the multivariable model, the adjusted OR for medial meniscal pathology was 4.14 (95% CI 2.06 to 8.31) for knee trauma during follow-up, 1.64 (1.00 to 2.70) for five or more bony enlargements of finger joints (vs ≤ 4) and 2.00 (1.18 to 3.40) for varus alignment (vs not varus) at baseline examination. Obesity was a risk factor for the development of meniscal extrusion, OR 3.04 (1.04 to 8.93) but not for meniscal lesions, OR 1.15 (0.52 to 2.54).

CONCLUSIONS

Apart from knee trauma, possible generalised osteoarthritis, expressed as multiple bony enlargements of finger joints, varus alignment and obesity are risk factors for medial meniscal pathology.

Systematic review of the concurrent and predictive validity of MRI biomarkers in OA

OBJECTIVE

To summarize literature on the concurrent and predictive validity of MRI-based measures of osteoarthritis (OA) structural change.

METHODS

An online literature search was conducted of the OVID, EMBASE, CINAHL, PsychInfo and Cochrane databases of articles published up to the time of the search, April 2009. 1338 abstracts obtained with this search were preliminarily screened for relevance by two reviewers. Of these, 243 were selected for data extraction for this analysis on validity as well as separate reviews on discriminate validity and diagnostic performance. Of these 142 manuscripts included data pertinent to concurrent validity and 61 manuscripts for the predictive validity review. For this analysis we extracted data on criterion (concurrent and predictive) validity from both longitudinal and cross-sectional studies for all synovial joint tissues as it relates to MRI measurement in OA.

RESULTS

Concurrent validity of MRI in OA has been examined compared to symptoms, radiography, histology/pathology, arthroscopy, CT, and alignment. The relation of bone marrow lesions, synovitis and effusion to pain was moderate to strong. There was a weak or no relation of cartilage morphology or meniscal tears to pain. The relation of cartilage morphology to radiographic OA and radiographic joint space was inconsistent. There was a higher frequency of meniscal tears, synovitis and other features in persons with radiographic OA. The relation of cartilage to other constructs including histology and arthroscopy was stronger. Predictive validity of MRI in OA has been examined for ability to predict total knee replacement (TKR), change in symptoms, radiographic progression as well as MRI progression. Quantitative cartilage volume change and presence of cartilage defects or bone marrow lesions are potential predictors of TKR.

CONCLUSION

MRI has inherent strengths and unique advantages in its ability to visualize multiple individual tissue pathologies relating to pain and also predict clinical outcome. The complex disease of OA which involves an array of tissue abnormalities is best imaged using this imaging tool.

Magnetic resonance imaging of the knee: clinical significance of common findings

Magnetic resonance imaging (MRI) of the knee is a widely used study that accurately depicts internal derangement. However, the relevance of the findings on knee MRI to the patient's symptoms and clinical course may often be uncertain. This article discusses the clinical significance and natural history of several common findings on knee MRI examinations.

The anatomical basis for a novel classification of osteoarthritis and allied disorders

Osteoarthritis (OA) has historically been classified as 'primary' where no discernible cause was evident and 'secondary' where a triggering factor was apparent. Irrespective of the triggering events, late-stage OA is usually characterized by articular cartilage attrition and consequently the anatomical basis for disease has been viewed in terms of cartilage. However, the widespread application of magnetic resonance imaging in early OA has confirmed several different anatomical abnormalities within diseased joints. A key observation has been that several types of primary or idiopathic OA show ligament-related pathology at the time of clinical presentation, so these categories of disease are no longer idiopathic - at least from the anatomical perspective. There is also ample evidence for OA initiation in other structures including menisci and bones in addition to articular cartilage. Therefore, a new classification for OA is proposed, which is based on the anatomical sites of earliest discernible joint structural involvement. The major proposed subgroups within this classification are ligament-, cartilage-, bone-, meniscal- and synovial-related, in addition to disease that is mixed pattern or multifocal in origin. We show how such a structural classification for OA provides a useful reference framework for staging the magnitude of disease. For late-stage or end-stage/whole organ disease, the final common pathway of these different scenarios, joint replacement strategies are likely to remain the only viable option. However, for younger subjects in particular, near the time of clinical disease onset, this scheme has implications for therapy targeted to specific anatomical locations. Thus, in the same way that tumours can be classified and staged according to their tissue of origin and extent of involvement, OA can likewise be anatomically classified and staged. This has implications for therapeutic strategies including regenerative medicine therapy development.

Chronic medial knee pain without history of prior trauma: correlation of pain at rest and during exercise using bone scintigraphy and MR imaging

OBJECTIVE

The objective of this study was to correlate chronic medial knee pain at rest and during exercise with bone scintigraphic uptake, bone marrow edema pattern (BMEP), cartilage lesions, meniscal tears, and collateral ligament pathologies on magnetic resonance MR imaging (MRI).

MATERIALS AND METHODS

Fifty consecutive patients with chronic medial knee pain seen at our institute were included in our study. Pain level at rest and during exercise was assessed using a visual analog scale (VAS). On MR images, BMEP volume was measured, and the integrity of femoro-tibial cartilage, medial meniscus, and medial collateral ligament (MCL) were assessed. Semiquantitative scintigraphic tracer uptake was measured. Multivariate linear regression analysis was performed.

RESULTS

At the day of examination, 40 patients reported medial knee pain at rest, 49 when climbing stairs (at rest mean VAS 33 mm, range 0-80 mm; climbing stairs mean VAS, 60 mm, range 20-100 mm). Bone scintigraphy showed increased tracer uptake in 36 patients (uptake factor, average 3.7, range 2.4-18.0). MRI showed BMEP in 31 studies (mean volume, 4,070 mm(3); range, 1,200-39,200 mm(3)). All patients with BMEP had abnormal bone scintigraphy. Ten percent of patients with pain at rest and 8% of patients with pain during exercise showed no BMEP but tracer uptake in scintigraphy. Tracer uptake and signal change around MCL predicted pain at rest significantly (tracer uptake p = 0.004; MCL signal changes p = 0.002). Only MCL signal changes predicted pain during exercise significantly (p = 0.001).

CONCLUSION

In chronic medial knee pain, increased tracer uptake in bone scintigraphy is more sensitive for medial knee pain than BMEP on MRI. Pain levels at rest and during exercise correlate with signal changes in and around the MCL.

Heberden's nodes and what Heberden could not see: the pivotal role of ligaments in the pathogenesis of early nodal osteoarthritis and beyond

Despite its relatively high prevalence, polyarticular nature, limited treatment options and recognized genetic contribution, the study of generalized OA (GOA) has lagged behind that of isolated knee OA. Whilst the pathogenesis of OA has been viewed in relation to either articular cartilage or bone disease, this article offers a viewpoint on why GOA may, in fact, be primarily a disorder of ligaments, and to a lesser extent tendon and joint capsule dysfunction. A relatively fast presentation of GOA, typically in the perimenopausal period, and its recognition on clinical grounds alone makes this type of OA potentially useful for pathogenic studies in OA, in general. The recent high-resolution MRI studies, microanatomical studies and animal models, in addition to established clinical and radiographic data that support this ligament-centric perspective of disease, are reviewed. The earliest structural abnormalities in GOA may be evident in ligaments and the ligament-associated 'enthesis organ', where degenerative changes are evident. Ligaments also influence the expression of joint damage including Heberden's node and joint erosion formation. Joint inflammation in a 'periarthritis' pattern is well recognized in GOA, and histological studies have shown that the ligament and capsule could represent the epicentre of such inflammatory changes. A perspective is also offered on how ligaments could play a pivotal role in OA in general; for example, the loss of joint space in knee OA due to meniscal extrusion could ultimately be related to derangement of the medial collateral ligament to which the meniscus is anchored.

MR Imaging of Cysts, Ganglia, and Bursae About the Knee

Cystic lesions around the knee comprise a diverse group of entities, ranging from benign cysts to complications of underlying diseases such as infection, arthritis, and malignancy. Their diverse causes result in varied prognoses and therapeutic options. Although the presentation of cystic masses may be similar, their management may differ, thus highlighting the importance of appropriate categorization. MR aids in the characterization of lesions by first localizing them, and then defining their relationship with adjacent structures and identifying any additional abnormalities. For the purpose of this article, the authors limit the scope of their discussion to benign cysts, ganglia, and bursae about the knee.