Posterior Medial Meniscus Root Ligament Lesions: MRI Classification and Associated Findings

1286 AJR:203, December 2014

tears are relatively common, particularly in the middle-aged or elderly population, and may be a cause of medial tibiofemoral osteo-arthritis of the knee, which is the most com-mon source of total knee arthroplasty [7, 8]. MRI is the primary diagnostic tool for PMMRL tears and has been regarded as both reliable and accurate for detection [4, 9].

Despite the growing orthopedic and im-aging literature on tears of the PMMRL, lit-tle information is currently available about the incidence of PMMRL lesions, classifi-cation of the lesion types, site of the failure, and other associated findings on MR images. The purposes of this study were to determine the prevalence of altered MRI appearances of PMMRL lesions, introduce a classification of lesion types, and report associated findings.

Materials and MethodsPatient Selection

This retrospective study was approved by the institutional review board of our institution, which

Posterior Medial Meniscus Root Ligament Lesions: MRI Classification and Associated Findings

Ja-Young Choi1 Eric Y. Chang2,3 Guilherme M. Cunha4 Monica Tafur3 Sheronda Statum3 Christine B. Chung2,3

Choi JY, Chang EY, Cunha GM, Tafur M, Statum S, Chung CB

1Department of Radiology, Seoul National University Hospital, Seoul, Korea.

2Department of Radiology, Veterans Administration San Diego Healthcare System, La Jolla, CA.

3Department of Radiology, University of California, San Diego Medical Center, 3350 La Jolla Village Dr, MC 114, San Diego, CA 92161. Address correspondence to E. Y. Chang ([email protected]).

4Department of Radiology, Clínica de diagnóstico por Imagem (CDPI), Rio de Janeiro, Brazil.

Musculoskeleta l Imaging • Or ig ina l Research

AJR 2014; 203:1286–1292

0361–803X/14/2036–1286

© American Roentgen Ray Society

The meniscal roots are ligament-like structures that serve to an-chor the fibrocartilaginous me-nisci onto the tibial intercondylar

fossa or intercondylar eminence [1, 2]. The role of the meniscal root is paramount; it pre-vents the meniscus from being extruded and allows the meniscus to generate hoop stress. This enables the menisci to effectively trans-fer the load from the femur to the tibia while protecting the articular cartilage of the knee from excessive load [2]. Therefore, complete tearing of a meniscal root results in complete loss of hoop stress, which is nearly function-ally identical to that of total meniscectomy [3] and a critical risk factor of early osteo-arthritis of the knee [4–6].

The “posterior medial meniscus root lig-ament (PMMRL)” attaches to the posterior intercondylar fossa between the attachments of the posterior root of the lateral meniscus and posterior cruciate ligament [1]. Several recent reports have suggested that PMMRL

Keywords: medial meniscus tear, MRI, posterior root ligament

DOI:10.2214/AJR.14.12559

Received January 19, 2014; accepted after revision March 21, 2014.

OBJECTIVE. The purposes of this study were to determine the prevalence of altered MRI appearances of “posterior medial meniscus root ligament (PMMRL)” lesions, introduce a classification of lesion types, and report associated findings.

MATERIALS AND METHODS. We retrospectively reviewed 419 knee MRI studies to identify the presence of PMMRL lesions. Classification was established on the basis of le-sions encountered. The medial compartment was assessed for medial meniscal tears in the meniscus proper, medial meniscal extrusion, insertional PMMRL osseous changes, regional synovitis, osteoarthritis, insufficiency fracture, and cruciate ligament abnormality.

RESULTS. PMMRL abnormalities occurred in 28.6% (120/419) of the studies: degenera-tion, 14.3% (60/419) and tear, 14.3% (60/419). Our classification system included degenera-tion and tearing. Tearing was categorized as partial or complete with delineation of the point of failure as entheseal, midsubstance, or junction to meniscus. Of all tears, 93.3% (56/60) oc-curred at the meniscal junction. Univariate analysis revealed significant differences between the knees with and without PMMRL lesions in age, medial meniscal tear, medial meniscal extrusion, insertional PMMRL osseous change, regional synovitis, osteoarthritis, insufficien-cy fracture (p = 0.017), and cruciate ligament degeneration (p < 0.001).

CONCLUSION. PMMRL lesions are commonly detected in symptomatic patients. We have introduced an MRI classification system. PMMRL lesions are significantly associated with age, medial meniscal tears, medial meniscal extrusion, insertional PMMRL osseous change, re-gional synovitis, osteoarthritis, insufficiency fracture, and cruciate ligament degeneration.

Choi et al.MRI of Posterior Medial Meniscus Root Ligament Lesions

Musculoskeletal ImagingOriginal Research

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AJR:203, December 2014 1287

MRI of Posterior Medial Meniscus Root Ligament Lesions

waived the requirement for informed consent. For enrollment of study subjects, we reviewed 500 consecutive knee MRI examinations at our insti-tution (from January to June 2012), which were performed on symptomatic patients. We excluded nine potential subjects with infectious or inflam-matory arthritis and benign or malignant tumors of the knee. In addition, we excluded 47 patients with a history of knee surgery or fractures around the knee. Twenty-five incomplete MRI studies were also excluded from the review. This left 419 MRI studies in 404 patients. The mean age of the patients was 45.7 years with an age range of 12–95 years. There were 194 men (mean age, 40.9 years; range, 12–77 years) and 225 women (mean age, 50.0 years; range, 13–95 years) and 216 right and 203 left knees.

MR Image AcquisitionPatients underwent knee MRI on 1.5-T (Sig-

na EchoSpeed HDX or TwinSpeed Excite, GE Healthcare) and 3-T (TwinSpeed, GE Health-care) systems with a knee coil. MRI protocols in-corporated the following sequences: sagittal fast spin-echo intermediate-weighted (TR range/TE, 2000–3800/15–33; echo-train length, 8; 3.5–4.0 mm section thickness; 0.5–1.0 mm interslice gap; 512 × 224 matrix; 14–15 cm FOV; and 1–2 signal averages), sagittal spin-echo T1-weight-ed (430–750/11–15; echo-train length, 2–4; 3.5–4.0 mm section thickness; 0.5–1.0 mm interslice gap; 320 × 256 matrix; 14–15 cm FOV; and 1 sig-nal average), sagittal fast spin-echo T2-weighted with fat saturation (2100–5300/60–75; echo-train length, 12; 3.5–4.0 mm section thickness; 0.5–1.0 mm interslice gap; 320 × 224 matrix; 14–15 cm FOV; and 1–2 signal averages), coronal fast spin-echo T2-weighted with fat saturation (2100–

5300/60–75; echo-train length, 8; 4-mm section thickness; 1-mm interslice gap; 320 × 256 ma-trix; 14-cm FOV, and 1 signal average), coronal spin-echo T1-weighted (383–750/11–15; echo-train length, 2; 4-mm section thickness, 1-mm in-terslice gap, 320 × 256 matrix, 14-cm FOV, and 1 signal average), and axial spin-echo intermedi-ate-weighted with fat saturation (3000–3300/25–40; echo-train length, 8; 4-mm section thickness; 1-mm interslice gap; 384 × 256 matrix; 15-cm FOV; and 2 signal averages).

MR Image AnalysisThe PMMRL was defined as extending from

the tibial attachment point to just lateral from the articular cartilage inflection point of the medi-al tibial plateau [10] (Fig. 1). The PMMRL was evaluated on all examinations, and lesions were classified into three groups on the basis of the fol-lowing definitions: degeneration, characterized by thickening of the root with intrasubstance hyper-intensity not contacting the articular surface; par-tial tear, characterized by abnormal signal inten-sity extending to the articular surface or abnormal morphology of the root with partial root disconti-nuity; and complete tear, characterized by com-plete discontinuity of the affected root (Fig. 2). When a PMMRL tear was present, the tear pattern was also categorized into one of two types: radial or transverse, characterized by a vertical tear per-pendicular to the longitudinal axis of the root lig-ament or longitudinal cleavage tear, characterized by a linear tear parallel to the longitudinal axis of the root ligament, which could be horizontally or vertically oriented (Fig. 3). Additionally, the point of failure was characterized as entheseal when it occurred at the tibial attachment point of the root ligament, midsubstance when it occurred within

the root ligament proper, or transition to the poste-rior horn of the medial meniscus (PHMM) when it occurred at the junction between the root and pos-terior horn (Fig. 1). We recorded all points if the tear occurred at more than one location.

All images were assessed for the presence of a medial meniscal tear in the meniscus proper, me-dial meniscal extrusion, insertional PMMRL os-seous changes, regional synovitis, insufficiency fracture, and cruciate ligament degeneration and tearing. A meniscus tear was designated when in-trasubstance signal intensity in the meniscus prop-er extended to an articular surface or abnormal meniscal morphology was noted on two or more images [11]. Medial meniscal tears were also sub-classified into those with or without continuous involvement into the PMMRL. Medial meniscal extrusion was designated present when the medi-al meniscal body extended greater than 3 mm pe-ripherally from the medial tibial plateau on the

Fig. 1—Drawing shows anatomy of posterior medial meniscus root ligament (PMMRL). PMMRL was defined as from tibial attachment point of root ligament to just lateral from articular cartilage inflection point of medial tibial plateau. Ligament was subcategorized into three zones: transition to posterior horn of medial meniscus at junction between root and posterior horn (a), midsubstance within root ligament proper (b), and entheseal at tibial attachment point of root ligament (c).

AFig. 2—MRI classification of posterior medial meniscus root ligament (PMMRL) lesions on sagittal fast spin-echo (FSE) intermediate-weighted (A, C, and E) and coronal FSE T2-weighted with fat saturation MR images (B, D, and F).A and B, MR images in 55-year-old man show degeneration. Localized intrasubstance hyperintensity within thickened root ligament (arrows) is seen with smooth surface. Outer smooth contour and total continuity of affected root ligament are preserved on consecutive sagittal images (not shown).

B

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Choi et al.

coronal images [12]. Insertional PMMRL osseous changes were designated present when there was focal bone marrow signal alteration, such as ede-malike or cystlike changes just beneath the tibial attachment point of the PMMRL (Fig. 4). Regional synovitis was designated present when intermedi-ate-hyperintense villous synovial proliferation on fluid-sensitive images was seen in the medial tib-iofemoral compartment. Insufficiency fracture was defined as a low-signal-intensity focus beneath the articular surface in the weightbearing area of the tibiofemoral compartment on T1-weighted images and central focal linear subchondral low-signal-intensity or focal subchondral bone plate impac-tion with marked surrounding bone marrow ede-ma on fat-suppressed T2-weighted images [13] (Fig. 5). Cruciate ligament degeneration was diag-nosed when the ligament showed increased signal

intensity, giving rise to an appearance similar to a stalk of celery [14] or associated cruciate ganglion cyst with fluidlike signal intensity in the substance of the ligament [15]. Cruciate ligament tear was designated when the ligament was discontinuous, thick or thin, amorphous, or hyperintense.

To determine the interobserver reliabilities of the MRI assessments of PMMRL lesions, two board-certified radiologists with 11 and 18 years of experience in knee MRI retrospectively reviewed 40 selected knee MRI studies independently that included 10 normal knees, 10 degenerations, 10 partial tears, and 10 complete tears of the root lig-ament and were randomly mixed. Intraobserver retest for reliability was determined by compar-ing the repeat MRI classification made by a single observer with a 12-week interval between evalu-ations. The interobserver and intraobserver reli-

ability for the presence of PMMRL lesions was evaluated using kappa statistics. The kappa coef-ficient of interobserver and intraobserver reliabili-ties for PMMRL lesion was 0.859 and 0.930, re-spectively, indicating almost perfect agreement. Thus, MRI analyses taken by a single observer were used in the analyses.

Radiographic Assessment of Knee OsteoarthritisRadiographic assessment of knee osteoarthritis

was carried out using weightbearing anteroposterior and supine lateral knee radiography interpreted by a musculoskeletal radiologist. On the basis of the Kell-gren-Lawrence (KL) radiographic osteoarthritis grading system [16], degrees of osteoarthritis in the tibiofemoral joint of the knee were assigned as five osteoarthritis grades: none (KL grade 0), doubtful (KL grade 1), minimal (KL grade 2), moderate (KL

EFig. 2 (continued)—MRI classification of posterior medial meniscus root ligament (PMMRL) lesions on sagittal fast spin-echo (FSE) intermediate-weighted (A, C, and E) and coronal FSE T2-weighted with fat saturation MR images (B, D, and F). C and D, MR images in 52-year-old woman show partial tear. Marked decrease (arrow) in cross-sectional area of root ligament is shown on sagittal image (C), but there is preserved continuity on consecutive sagittal images (not shown). Coronal image (D) shows focal deep defect (arrow) of affected root ligament at transition to posterior horn of medial meniscus (PHMM) with wavy residual root ligament.E and F, MR images in 33-year-old woman show complete tear. Root ligament is completely absent at transition to PHMM on sagittal image (E). Fluid-filled full-thickness cleft (arrow) is also seen on coronal image (F).

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grade 3), and severe (KL grade 4). Radiographic tibiofemoral osteoarthritis was considered present if the KL grade was 2 or higher.

Statistical AnalysisThe prevalence of PMMRL lesions and propor-

tion of each lesion type were computed. The vari-ous clinical and radiologic parameters were statis-tically tested using univariate analysis. The Student t test was performed for quantitative variables, and a Pearson chi-square test was used for qualitative variables. All statistical analyses were carried out using SPSS for Windows, version 18.0, and p values of < 0.05 were considered significant throughout.

ResultsPMMRL lesions were found in 120

(28.6%) of 419 knees: degeneration in 60 (14.3%) knees, partial tear in 49 (11.7%), and complete tear in 11 (2.6%). Of the 60 PMMRL tears, radial or transverse tears were seen in 41 (68.3%) knees and longitu-dinal cleavage in 13 (21.7%), and miscella-neous tears in 6 (10.0%). In terms of the point of failure, most of the tears (56 tears, 93.3%) involved the junction to the PHMM: 33 (55%) involved only the junction to PHMM whereas 23 (38.3%) involved both the junc-tion and midsubstance of the root ligament. The tears at the midsubstance and entheseal portions were only found in two (3.3%) and two (3.3%) knees, respectively.

Results of assessments for concurrent MRI findings are summarized in Table 1. Medial meniscal tears in the meniscus proper were found in 166 (39.6%) of 419 knees and, inter-estingly, most PMMRL lesions (104 of 120 le-

sions, 86.7%) were accompanied by a tear in the meniscus proper. Moreover, 39 (65%) of 60 PMMRL tears were directly continuous with an adjacent medial meniscal tear. Uni-variate analysis revealed a significant dif-ference between the knees with and without PMMRL lesions in patient age, medial menis-cal tear, medial meniscal extrusion, insertion-al PMMRL osseous change, regional synovi-tis, osteoarthritis, insufficiency fracture, and cruciate ligament degeneration (Table 1).

DiscussionTears of the PMMRL continue to receive

increasing attention in the literature, largely

due to wide recognition of the importance of this structure. Nevertheless, detailed informa-tion on the PMMRL in terms of frequency, types, and associated factors is not well estab-lished. This study aimed to address these un-clear issues related to the PMMRL lesion.

In our study, PMMRL lesions, including degeneration and tearing, were frequent find-ings. Among 419 consecutive knees undergo-ing MRI for knee symptoms, we found root ligament lesions in 28.6%, including tears in 14.3%. Previous studies have shown wide variability in prevalence of PMMRL tears, ranging from 0.4 to 29.5% [7, 9, 12, 17–20]. It is likely that the variability in PMMRL

TABLE 1: Characteristics of Knees With and Without Posterior Medial Meniscus Root Ligament (PMMRL) Lesions

Parameters

PMMRL Lesions

No (n = 299, 71.4) Yes (n = 120, 28.6) p

Mean age ± SD (y) 41.4 ± 16.0 56.6 ± 15.7 < 0.001

Sex (male:female) 143:156 51:69 0.332

Medial meniscal tear in meniscus proper 62 (20.7) 104 (86.7) < 0.001

Medial meniscal extrusion 23 (7.7) 61 (50.8) < 0.001

Insertional PMMRL osseous changes 17 (5.7) 43 (35.8) < 0.001

Regional synovitis 23 (7.7) 56 (46.7) < 0.001

Osteoarthritis 27 (9.0) 51 (42.5) < 0.001

Insufficiency fracture 11 (3.7) 12 (10) 0.017

Anterior cruciate ligament tear 47 (15.7) 14 (11.7) 0.358

Anterior cruciate ligament degeneration 14 (4.7) 29 (24.2) < 0.001

Posterior cruciate ligament tear 11 (3.7) 3 (2.5) 0.765

Posterior cruciate ligament degeneration 2 (0.7) 11 (9.2) < 0.001

Note—Data in parentheses are percentages. Statistically significant values (p < 0.05) are shown in bold.

A BFig. 3—Two patterns of posterior medial meniscus root ligament (PMMRL) tears on sagittal fast spin-echo (FSE) intermediate-weighted (A and C) and coronal FSE T2-weighted with fat saturation MR images (B and D).A and B, MR images in 67-year-old woman show radial or transverse tear. Nondelineation of root ligament (arrow) is noted on only one sagittal image (A). Full-thickness defect at transition to posterior horn of medial meniscus (arrow, B) is seen, direction of which is perpendicular to longitudinal axis of root ligament.

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tear prevalence is a result of a combination of factors, including different patient popu-lations; differences in diagnostic methods (imaging vs arthroscopy); and differences in definition, including location and inclusion of partial tears.

Most studies have used binary classifica-tion systems for meniscal root tears: nor-mal or tearing and, most frequently, either a radial tear or avulsion at the insertion of the meniscus [18, 21, 22]. However, besides those types, our assessments have revealed

that PMMRL tears can be further classified into additional subtypes, such as longitudi-nal cleavage tear. We believe that longitudi-nal cleavage tears of the PMMRL may result from direct extension of preceding PHMM tears into the adjacent root ligament. Howev-er, this hypothesis warrants future indepen-dent longitudinal studies for confirmation. In terms of the point of failure, we observed that PMMRL tears mostly commonly occur at the junction with the PHMM followed by the midsubstance, and they least common-

ly manifest as an avulsion at the enthesis. A previous animal study had similar results regarding the most frequent point of failure [23]. Possibly, this is because the PMMRL is the stiffest meniscal attachment among all of the root ligaments and thus would be unique-ly predisposed to injury at the junction with the PHMM during activities [24]. Moreover, the junction between the posterior horn and the root ligament may be structurally weak-er because of the differences in morphology and collagen distribution between the fibro-cartilagenous meniscus, root ligament, and enthesis [1, 25]. Additionally, PMMRLs are exposed to more stressful conditions in both tensile and compressive loads, whereas the anterior root ligaments are mostly exposed only to tensile loads [25].

We believe that a detailed description of PMMRL pathology would be helpful for or-thopedic surgeons to manage PMMRL tears in clinical practice. Conventionally, PMMRL tears have been treated by meniscectomy [26, 27]. However, because recent biomechani-cal studies have revealed significant chang-es in contact pressure and knee joint kine-matics due to PMMRL tears [3, 28], several techniques for meniscal root repair to restore joint biomechanics to near normal condi-tions have been developed. These techniques fall into two broad categories: transosseous suture repairs and suture anchor repairs [29–34]. In the case of transosseous suture re-pair, suture capturing should be performed approximately 2–3 mm from the edge of the tear; however, if a PMMRL tear occurs at the junction with the PHMM, capturing the pos-terior horn may create excessive tension on

CFig. 3 (continued)—Two patterns of posterior medial meniscus root ligament (PMMRL) tears on sagittal fast spin-echo (FSE) intermediate-weighted (A and C) and coronal FSE T2-weighted with fat saturation MR images (B and D).C and D, MR images in 63-year-old man show longitudinal cleavage tear. Linear fluid-equivalent hyperintensity (arrow) splitting root ligament into superior and inferior halves is seen on sagittal image (C). This lesion (asterisk, D) involves nearly whole length of root ligament, parallel to its longitudinal axis.

D

Fig. 4—52-year-old woman with tibial posterior medial meniscus root ligament (PMMRL) insertional osseous change. Sagittal fast spin-echo T2-weighted MR image with fat suppression shows tiny cystic lesion (solid arrow) in subcortical bone marrow of tibia near root ligament tibial attachment. Small less hyperintense area (arrowhead) considered as bone marrow edemalike change is also noted in anterosuperior aspect of aforementioned cystic change. Partial tear (open arrow) of root ligament is seen.

Fig. 5—73-year-old woman with posterior medial meniscus root ligament (PMMRL) tear and femoral insufficiency fracture. On coronal fat-suppressed fast spin-echo T2-weighted MR image, focal dark line (solid arrow) considered as insufficiency fracture is seen in subchondral area of distal femur. Associated large bone marrow edemalike change (arrowheads) surrounding fracture is noted. In addition, meniscal extrusion (> 3 mm) (open arrow) is observed. PMMRL tear is not shown.

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the meniscal body and placing the sutures too close to the tear edge may result in su-ture cut-out and loss of fixation [29]. In ad-dition, the further away the PMMRL tear is from the entheseal portion, the less favorable characteristics it could have for healing be-cause the PMMRL is vascularized and ame-nable to repair whereas the paracentral pos-terior horn region is not [21, 35]. Thus, we believe that reporting more detailed infor-mation about the tear location, pattern, and adjacent PHMM would be more valuable to establish a management plan, such as repair, meniscectomy, or observation with conser-vative management, compared with simply reporting “root tear.”

On the basis of our results, age, medi-al meniscal tear, medial meniscal extru-sion (> 3 mm), insertional PMMRL osseous changes, regional synovitis, osteoarthritis, insufficiency fracture, and cruciate ligament degeneration were significantly different be-tween the knees with and without PMMRL lesions. PMMRL lesions were more frequent in elderly persons, similar to the results from previous reports [7, 8]. However, contrary to previous reports of female predominance, our results revealed no significant difference in between sexes. This discrepancy may re-sult from the different characteristics be-tween study cohorts. Regarding the associ-ation with a medial meniscal proper tear, a previous study reported that 18% of PMMRL tears were accompanied by medial meniscal tears [22], whereas our study found that ap-proximately 83% (50 of 60 PMMRL tears) of PMMRL tears were accompanied by me-dial meniscal tears at the meniscus proper. In addition to sample differences, an expla-nation for our different rates could be the differences in definition of the root because Lee et al. [22] defined the root as occurring within 5 mm of the tibial attachment, where-as we defined the root as beginning lateral to the articular cartilage inflection point of the medial tibial plateau, similar to other authors [10]. As one of the main reasons, we postu-late that medial displacement of the posteri-or horn after a PMMRL tear may cause the posterior horn to be injured by direct friction between the femoral and tibial articular sur-faces. Thus, when a PMMRL tear is detect-ed on MRI, attention should be paid to find a concomitant medial meniscal tear in the me-niscus proper and vice versa. As for menis-cal extrusion, prior research has indicated that it is associated with meniscal root tear-ing [5, 6, 12, 22], and this is consistent with

the results of our study. Regarding the inser-tional PMMRL osseous change at the tibi-al intercondylar area, to date, little informa-tion is available about its incidence and the relationship with PMMRL lesion. Its cause is not clear. We presume that these insertion-al PMMRL osseous changes, including in-traosseous bone marrow signal alteration or cystic change, may stem from repetitive ab-normal stress, such as traction force on the bone at the root ligament attachment site that may cause focal necrosis with liquefac-tion and ganglion formation [36]. Didolkar and Vinson [37] also suggested that cysts lo-cated at the insertions of the medial menis-cus had a statistically significant association with meniscal abnormality. Regarding re-gional synovitis, the higher frequency in the knees with PMMRL lesions may be partly attributed to the abundant vascular distribu-tion in the root ligament, which may allow production of an inflammatory response. Os-teoarthritis was more frequently present in the knees with PMMRL lesions, as previous-ly described in the literature [12, 17, 21, 22]. The higher incidence of insufficiency frac-ture in the knees with PMMRL lesions in this study is correspondent with previous re-ports [19, 38, 39]. Interestingly, we observed that cruciate ligament degeneration was sig-nificantly more frequent in the knees with PMMRL lesions. To our knowledge, there have been no reports regarding this relation-ship. We believe that PMMRL lesions and cruciate ligament degeneration may be relat-ed to degeneration and aging.

Some limitations of this study warrant consideration. First, we did not provide con-firmatory arthroscopic findings for our MRI findings. Nevertheless, knee MRI has a well-known high accuracy for diagnosis of menis-cal root tear, with sensitivity of 85–96% and specificity of 94–100% [9, 22, 38]. Addi-tionally, it is difficult to visualize the entire PMMRL on routine arthroscopy, and degen-eration may not be visible. Second, this study provided information on the relationship be-tween several factors and PMMRL ligament lesions. Nevertheless, because of the cross-sectional nature of our study, we are not able to draw definite conclusions of causal rela-tionships of associated factors and PMMRL lesions. Further longitudinal studies are re-quired to reveal the risk factors for PMMRL lesions. Finally, our study population was not representative of the general population be-cause we enrolled only symptomatic subjects warranting knee MRI. However, our popu-

lation more closely represents that which would be encountered in daily practice at a tertiary care center.

In conclusion, PMMRL lesions are com-monly detected in symptomatic patients. We have introduced an MRI classification sys-tem. PMMRL lesions are significantly asso-ciated with age, medial meniscal tears, me-dial meniscal extrusion, insertional PMMRL osseous change, regional synovitis, osteo-arthritis, insufficiency fracture, and cruciate ligament degeneration.

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Documents

Posterior Medial Meniscus Root Ligament Lesions: MRI Classification and Associated Findings