Intrameniscal Signal Intensity Research Articles

More than 3 mm of preoperative medial meniscal extrusion is identified as a key risk factor for varus progression in limb alignment after arthroscopic repair of medial meniscus posterior root tear.

To investigate the risk factors for varus progression after arthroscopic medial meniscal posterior root tear (MMPRT) repair and to compare the clinical outcomes between two groups: one with more varus progression and the other with less varus progression. Patients who underwent isolated arthroscopic repair of MMPRT between 2015 and 2020 were enroled, and 2-year follow-up data were collected. Participants were categorized into two groups based on preoperative values of the weight-bearing line (WBL) ratio: group A with <5.9% increase and group B with ≥5.9% increase. Various factors, including demographic features and radiological findings, were analysed and compared between the two groups. Intra-meniscal signal intensity, meniscal healing, medial meniscal extrusion (MME), and articular cartilage grade were assessed preoperatively and 1-year postoperatively using coronal magnetic resonance imaging. The final cohort consisted of 34 patients in group A and 46 in group B, with a mean age of 55.8 ± 11.2 and 59.8 ± 6.6 years, respectively. Preoperative WBL ratio and cartilage lesions in the medial compartment did not differ between the groups. Preoperative MME were significantly lower in group A than those in group B (2.6 ± 0.6 mm in group A and 3.5 ± 0.7 mm in group B, p < 0.05). Patient-reported outcomes at the 2-year follow-up did not differ between the two groups (n. s.). In a logistic analysis, the odds ratio of MME was 2.1 (p < 0.05), and the cutoff value of MME was 3.02 mm. Preoperative MME is a risk factor for varus progression. However, no differences in patient-reported outcomes were observed at 2-year follow-up, even in the group with greater varus progression. Level IV.

Intrameniscal degeneration and meniscotibial ligament loosening are associated factors with meniscal extrusion of symptomatic discoid lateral meniscus.

This study aimed to compare the amount of extrusion of the discoid lateral meniscus (DLM), which was symptomatic and required surgery, with normal meniscuses and asymptomatic DLMs and examine factors associated with the extrusion of symptomatic DLM. Medical records of participants with DLM or normal lateral meniscus (LM) were retrospectively reviewed using magnetic resonance imaging (MRI). DLM cases were divided into symptomatic and asymptomatic groups. The midbody meniscal extrusion was measured using mid-coronal MRI. The association between meniscal extrusion and MRI findings, including the meniscofemoral ligament, meniscotibial ligament (MTL), intrameniscal signal intensity of the peripheral rim, meniscal shift, and skeletal maturity, was evaluated. Eighty-six knees with DLM (63 symptomatic) were included. The control group included 31 patients. The symptomatic group showed significantly greater meniscal extrusion (mean ± standard deviation symptomatic DLM: 1.0 ± 1.1mm, asymptomatic DLM: 0.1 ± 0.4mm, and normal LM: 0.3 ± 0.6mm, P < 0.001) and had a significantly higher incidence of MTL loosening (P = 0.02) and intrameniscal signal (P < 0.001) than the other two groups. In the symptomatic group, multivariable linear regression analysis showed that MTL loosening [β = 1.45, 95% confidence interval (CI) 1.03-1.86, P < 0.001] and intrameniscal signal (β = 0.49, 95% CI 0.09-0.90, P = 0.002) were independent associated factors. LM extrusion was significantly more common in patients with symptomatic DLM than in those with asymptomatic DLM or a normal LM. MTL loosening and intrameniscal high-signal intensity on MRI were independently associated with meniscal extrusion. These findings help explain the pathogenesis and diagnosis of symptomatic DLM. III.

Assessment of Anatomic Restoration and Clinical Outcomes Between Medial and Lateral Meniscal Allograft Transplantation.

Background:Proper anatomic restoration is an important consideration for meniscal allograft transplantation (MAT), even with the different anatomica characteristics between the medial meniscus and lateral meniscus.Purpose/Hypothesis:The purpose of this study was to assess the accuracy of anatomic restoration in medial and lateral MAT (MMAT and LMAT) procedures and to compare their outcomes. We hypothesized that (1) the anatomic differences between the medial and lateral menisci will mean a less accurate anatomic restoration for MMAT and (2) clinical outcomes after MMAT will be inferior compared with LMAT.Study Design:Cohort study; Level of evidence, 3.Methods:We retrospectively evaluated 20 patients who underwent MMAT using the bone plug technique and 21 patients who underwent LMAT using the keyhole technique at a single institution from July 2014 to June 2019. Demographic data, previous surgeries, and concomitant procedures were recorded, as were lower limb alignment and osteoarthritis grade on radiographs. Using preoperative and follow-up magnetic resonance imaging, the meniscal position, rotation, extrusion, and intrameniscal signal intensity were evaluated. Clinical outcomes were evaluated using the International Knee Documentation Committee and Lysholm scores.Results:The mean follow-up was 41.15 ± 18.86 and 45.43 ± 21.32 months for the MMAT and LMAT patients, respectively. Concomitant procedures were performed in 90% of MMATs and 15% of LMATs. There was no significant difference between the native and postoperative root positions after LMAT; however, for MMAT, the position of the anterior root was located significantly posteriorly (P = .002) and medially (P = .007) compared with preoperatively. In addition, the allograft medial meniscus was restored in a more internally rotated position (P = .029). MMATs also exhibited significantly increased meniscal extrusion compared with LMATs (posterior horn, P < .001; midbody, P = .027; anterior horn, P = .006). However, there was no significant difference between the 2 groups at final follow-up in intrameniscal signal intensity or clinical scores.Conclusion:LMAT showed higher accuracy than MMAT in restoring meniscal position and rotation, and there was less meniscal extrusion. However, clinical scores improved after both LMAT and MMAT compared with preoperative values, and midterm clinical outcomes were similar. The small anatomical errors seen in the MMAT technique were not clinically relevant at midterm follow-up.

Two simple stitches for medial meniscus posterior root repair prevents the progression of meniscal extrusion and reduces intrameniscal signal intensity better than modified Mason-Allen sutures.

Medial meniscus posterior root tears (MMPRTs) can cause severe medial extrusion of the medial meniscus (MMME) and the progression of knee degenerative changes, inducing a high signal intensity of the meniscus on magnetic resonance imaging (MRI). Although MMME and intrameniscal signal intensity (IMSI) reportedly decreased within 3months after MMPRT repair, no previous studies have reported these changes after a 1-year follow-up. This study aimed to investigate the 1-year postoperative changes in MMME and IMSI on MRI after using different suture techniques. Overall, 33 patients with MMPRT were evaluated, 22 underwent FasT-Fix-dependent modified Mason-Allen suture (F-MMA) repair, and 11 underwent two simple stitches (TSS) repair. MRI examinations were performed preoperatively and 1year postoperatively. MMME and IMSI were determined using MRI. A significant decrease in postoperative MMME was observed in the TSS group (4.1 ± 1.0) relative to that in the F-MMA group (5.1 ± 1.4, P = 0.03). A significant decrease in postoperative IMSI (0.75 ± 0.14) was observed relative to preoperative IMSI in the TSS group (P < 0.01), whereas postoperative IMSI (0.94 ± 0.25) was similar to preoperative IMSI in the F-MMA group (P = 0.06). Furthermore, a significant decrease in postoperative IMSI was observed in the TSS group relative to that in the F-MMA group (P < 0.01). The most important finding of this study is that TSS repair yielded a greater decrease in MMME and IMSI than F-MMA repair in patients with MMPRT. These results suggest that TSS repair is more useful for restoring loading stress to the posterior horn of the medial meniscus.

Effet de l’atélocollagène sur la cicatrisation des réparations de la racine méniscale médiale à l’aide du point Mason–Allen modifié

IntroductionAddition of collagen during medial meniscal root repair (MMRR) may improve meniscal root healing minimizing fibrous scar tissue formation. The purpose of this study was to verify the effect of atelocollagen on MMRR using the modified Mason–Allen stitch when compared with that of the conventional pull-out repair by assessing the clinical and radiological outcomes. HypothesisIt was hypothesized that atelocollagen would enhance the healing effect on the meniscal root following MMRR. Moreover, we presumed that MMRR with atelocollagen application might reduce meniscal extrusion by promoting healing. Materials and methodsA total of 47 patients who underwent MMRR using the modified Mason–Allen stitch between 2015 and 2016 were included, and they were divided into group A (atelocollagen application; n=25) and group R (MMRR without atelocollagen application; n=22). The postoperative clinical outcomes, radiological outcomes, and meniscal root healing and medial compartment cartilage status on follow-up magnetic resonance imaging (MRI) were compared between the two groups. ResultsMean follow-up duration was 26.4±4.8 months in group A and 27.1±5.2 months in group R (p=0.598). Mean duration from surgery to follow-up MRI was 12.5±1.4 months in group A and 12.7±1.2 months in group R (p=0.604). The subjective knee scores improved significantly in both groups at the last follow-up (all, p<0.001). The Kellgren–Lawrence (K-L) grade progressed in 16% and 22.7% in group A and group R, respectively (p=0.351). Follow-up MRI showed progression of cartilage loss in the medial compartment in 28% and 40.9% in group A and group R, respectively (p=0.355). In terms of meniscal root healing, 18 (72%) and 12 (54.5%) patients had complete healing, and 6 (24%) and 8 (36.4%) patients had partial healing in groups A and R, respectively. The mean value of the intrameniscal signal intensity (IMSI) of the meniscal root based on MRI in group A was significantly lower than that in group R (p<0.001). The medial meniscal extrusion in groups A and R decreased by 0.2±0.1mm and 0.1±0.3mm following MMRR without significant differences (p=0.056 and p=0.229, respectively). The IMSI presented significant negative correlations with the root healing status and significant positive correlations with K-L grade progression (p<0.05). DiscussionAtelocollagen application during MMRR yielded lower IMSIs, suggesting better healing, than did conventional pull-out root repair. However, this technique could not demonstrate beneficial effects on meniscal extrusion. Level of evidenceIII, retrospective case-control study.

Effect of atelocollagen on the healing status after medial meniscal root repair using the modified Mason–Allen stitch

IntroductionAddition of collagen during medial meniscal root repair (MMRR) may improve meniscal root healing minimising fibrous scar tissue formation. The purpose of this study was to verify the effect of atelocollagen on MMRR using the modified Mason–Allen stitch when compared with that of the conventional pullout repair by assessing the clinical and radiological outcomes. HypothesisIt was hypothesised that atelocollagen would enhance the healing effect on the meniscal root following MMRR. Moreover, we presumed that MMRR with atelocollagen application might reduce meniscal extrusion by promoting healing. Materials and methodsA total of 47 patients who underwent MMRR using the modified Mason–Allen stitch between 2015 and 2016 were included, and they were divided into group A (atelocollagen application; n=25) and group R (MMRR without atelocollagen application; n=22). The postoperative clinical outcomes, radiological outcomes, and meniscal root healing and medial compartment cartilage status on follow-up magnetic resonance imaging (MRI) were compared between the two groups. ResultsMean follow-up duration was 26.4±4.8 months in group A and 27.1±5.2 months in group R (p=0.598). Mean duration from surgery to follow-up MRI was 12.5±1.4 months in group A and 12.7±1.2 months in group R (p=0.604). The subjective knee scores improved significantly in both groups at the last follow-up (all, p<0.001). The Kellgren–Lawrence (K–L) grade progressed in 16% and 22.7% in group A and group R, respectively (p=0.351). Follow-up MRI showed progression of cartilage loss in the medial compartment in 28% and 40.9% in group A and group R, respectively (p=0.355). In terms of meniscal root healing, 18 (72%) and 12 (54.5%) patients had complete healing, and 6 (24%) and 8 (36.4%) patients had partial healing in groups A and R, respectively. The mean value of the intra-meniscal signal intensity (IMSI) of the meniscal root based on MRI in group A was significantly lower than that in group R (p<0.001). The medial meniscal extrusion in groups A and R decreased by 0.2±0.1mm and 0.1±0.3mm following MMRR without significant differences (p=0.056 and p=0.229, respectively). The IMSI presented significant negative correlations with the root healing status and significant positive correlations with K–L grade progression (p<0.05). DiscussionAtelocollagen application during MMRR yielded lower IMSIs, suggesting better healing, than did conventional pullout root repair. However, this technique could not demonstrate beneficial effects on meniscal extrusion. Level of evidenceIII, retrospective case-control study.

Extrusions do not affect degenerative morphologic changes in lateral meniscus allografts during midterm follow-ups.

To investigate degenerative morphological changes in meniscus allograft after lateral meniscus allograft transplantation (MAT) based on extrusions. Ninety-one patients who underwent lateral MAT were divided into extruded and non-extruded groups. Serial magnetic resonance imaging scans obtained 6weeks, 1year, and at the last follow-up (midterm, 3-7years) post-surgery were evaluated retrospectively. Degenerative morphological changes at each time point in each group were compared using the postoperative meniscal width, thickness, and intrameniscal signal intensity (IMSI) at the anterior horn, mid-body, and posterior horn. The Lysholm scores and meniscal tears based on graft extrusion were also investigated. The mean age was 33.7 ± 11.1years (64 men and 27 women). Fifty-three (58%) and 38 knees (42%) were classified into the non-extruded and extruded groups, respectively. The overall meniscal width of the mid-body decreased from 9.6 ± 1.3 to 6.5 ± 1.2mm (p < 0.01), and IMSI of mid-body was increased from 1.2 ± 0.1 to 1.7 ± 0.1 (p < 0.01) during midterm follow-ups. No significant differences were observed between the meniscal width, thickness, and IMSI at the anterior horn (n.s.), mid-body (n.s.), and posterior horn (n.s.) of the two groups during the midterm follow-ups. The incidence of meniscus tears and Lysholm scores did not differ significantly between the groups during midterm follow-ups. The overall meniscus width of mid-body decreased while the relative IMSI of mid-body increased during midterm follow-ups after lateral MAT. Meniscal allograft extrusions did not influence postoperative changes in meniscus width, thickness, and relative intrameniscal signal intensity. Level III.

Pullout Repair of the Medial Meniscus Posterior Root Tear Reduces Proton Density-Weighted Imaging Signal Intensity of the Medial Meniscus.

Medial meniscus (MM) posterior root tear (PRT) results in joint overloading and degenerative changes in the knee. MM root repair is recommended to prevent subsequent cartilage degeneration following MMPRT. Favorable clinical outcomes have been reported after transtibial pullout repair of MMPRT. However, it is unclear whether pullout repair can cause compositional change in the MM posterior segment. We examined this question in 14 patients who underwent MMPRT pullout repair. Magnetic resonance imaging examinations were performed preoperatively and 3 months postoperatively at 10° knee flexion. The region-of-interest was marked along the MM posterior segment edge. Intra-meniscal signal intensity (IMSI) was expressed as the signal intensity ratio of the repaired MM to the intact lateral meniscus, which was used as a control. MMPRT pullout repair reduced IMSI from 1 to 0.915±0.096 (range, 0.760-1.074) 3 months postoperatively (p=0.006, power=0.90). Meniscal degeneration causes high proton density-weighted imaging signal intensity of the meniscal body. In our study, MMPRT pullout repair reduced IMSI contrary to other tears. This technique may decrease the MM posterior segment signal intensity by restoring the hoop tension mechanism. Measuring IMSI may be useful to assess the effect of MMPRT pullout repair on meniscal healing.

Evolution of Intrameniscal Signal-Intensity Alterations Detected on MRI Over 24 Months in Patients With Traumatic Anterior Cruciate Ligament Tear.

The objective of our study was to assess the prevalence and evolution of intrameniscal signal-intensity alteration in subjects with an anterior cruciate ligament (ACL) tear over 24 months and compare clinical outcome and changes of cartilage between subjects with and those without this meniscal abnormality. Fifty-seven subjects with an ACL tear were screened for intrameniscal signal-intensity alteration. Morphologic and compositional MRI was performed before ACL reconstruction and 12 and 24 months after ACL reconstruction. Twelve subjects with an intrameniscal signal-intensity alteration and 12 subjects without any meniscal abnormality on MRI were identified. Clinical outcome was measured using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and T1ρ and T2 maps of the cartilage were obtained. In 10 of 12 subjects (83%) the meniscal signal-intensity abnormality identified on baseline MRI was located at the posterior horn of the medial meniscus. None of these subjects presented with a meniscal tear over 24 months of follow-up. At 12 months after the ACL tear, the intrameniscal signal-intensity alteration detected on baseline MRI had completely resolved in seven of 12 subjects (58%), showed a signal-intensity decrease in four (33%), and remained stable in one subject (8%). Of the 10 subjects who underwent MRI at 24 months, the meniscal signal-intensity alteration had completely resolved in eight (80%), and the signal intensity had decreased in the other two subjects. Changes in the KOOS and cartilage T1ρ and T2 values from baseline and 24 months did not differ significantly between subjects with and those without intrameniscal signal-intensity alteration (p > 0.05). High intrameniscal signal-intensity alterations are a common finding in subjects with an ACL tear and have a benign course over 24 months after surgical repair of the ACL tear.

Natural History of Intrameniscal Signal Intensity on Knee MR Images: Six Years of Data from the Osteoarthritis Initiative.

To assess the natural history of intrameniscal signal intensity on magnetic resonance (MR) images of the medial compartment. Both knees of 269 participants (55% women, aged 45-55 years) in the Osteoarthritis Initiative without radiographic knee osteoarthritis (OA) and without medial meniscal tear at baseline were studied. One radiologist assessed 3-T MR images from baseline and 24-, 48-, and 72-month follow-up for intrameniscal signal intensity and tears. A complementary log-log model with random effect was used to evaluate the risk of medial meniscal tear, adjusting for age, sex, body mass index, and knee side. At baseline, linear intrameniscal signal intensity in the medial compartment was present in 140 knees (26%). Once present, regression only in a single knee was observed. In 31 knees (19%) with linear intrameniscal signal intensity at any of the first three time points, the signal intensity progressed to a tear in the same segment, and in a single knee, the tear occurred in an adjacent segment. The corresponding number of tears without prior finding of intrameniscal signal intensities was 11 (3%). In the adjusted model, the hazard ratio for developing medial meniscal tear was 18.2 (95% confidence interval: 8.3, 39.8) if linear intrameniscal signal intensity was present, compared when there was no linear signal intensity. There was only one of 43 knees with injury reported in conjunction with the incident tear. In middle-aged persons without OA, linear intrameniscal signal intensity on MR images is highly unlikely to resolve and should be considered a risk factor for medial degenerative meniscal tear.

Changes in Magnetic Resonance Imaging Signal Intensity of Transplanted Meniscus Allografts Are Not Associated With Clinical Outcomes

To evaluate changes in intrameniscal signal intensity (IMSI) of transplanted allografts during the first year after meniscus allograft transplantation (MAT) by use of serial magnetic resonance imaging, as well as to analyze the relation between IMSI and clinical outcome. This prospective study involved 43 patients who underwent MAT between 2006 and 2007 after diagnosis of total or subtotal meniscectomized knees. The mean patient age at the time of surgery was 35.8 years (range, 17 to 46 years). Allografts were assessed by conventional magnetic resonance imaging performed at 6 weeks and 3, 6, and 12 months after MAT. The ratio of the signal intensity of the transplanted meniscus allograft to that of the control normal meniscus in the ipsilateral knee was calculated to obtain a standardized signal intensity value. IMSI was assessed in terms of postoperative time and location (anterior v posterior horn). The Lysholm score was used to evaluate knee function. The IMSI of transplanted allograft menisci was higher than that for nontransplanted menisci at all 4 postoperative time points (P < .01). The anterior horn allograft IMSI was greater than the posterior horn allograft IMSI at all time points (P < .01). The allograft IMSI increased starting 3 months postoperatively for the anterior horn (F(3,40) = 7.5, P < .01) and 6 months postoperatively for the posterior horn (F(3,40) = 9.2, P < .01). These increases were maintained to the final assessment at 1 year postoperatively. No correlation was found between IMSI and postoperative Lysholm score. Transplanted allograft menisci had higher signal intensities than normal menisci. Signal intensity was higher for the anterior horn than the posterior horn throughout the first postoperative year. Signal intensity increased over time, and this increase was maintained at 1 year postoperatively. However, signal intensity was not related to clinical outcome. Level II, development of diagnostic criteria based on analysis of consecutive patients, applying a universally recognized gold standard.

New observations on meniscal cysts

The purpose of this study was to determine the incidence of meniscal cysts, assess the frequency of various magnetic resonance (MR) imaging characteristics, and emphasize radiographic observations not commonly reported. A total of 2,095 consecutive knee MR imaging reports from a 22 month period were retrospectively reviewed for the presence of meniscal cysts. Two musculoskeletal radiologists reviewed the cases where cysts were reported. A meniscal cyst was considered present if abnormally increased signal was identified within an enlarged meniscus (i.e., intrameniscal cyst) or if a loculated fluid-intensity lesion with a clear connection to the adjacent meniscus was identified (i.e., parameniscal cyst). Presence or absence of a meniscal tear, intrameniscal and parameniscal signal intensity, patient age, sex, location of meniscal cyst, presence of discoid meniscus, and size of the parameniscal cyst component were recorded. All knee imaging examinations were performed on a 1.5T MR unit. Imaging findings were correlated with arthroscopic reports when available. A total of 167 cases (8.0%) of meniscal cysts were diagnosed in 161 patients. Of the 167 cysts, 69 (41.3%) were located in the lateral meniscus and 98 (58.7%) in the medial meniscus. In 6 patients (3.7%), meniscal cysts were present in both menisci of the same knee. Twelve (7.2%) meniscal cysts were associated with discoid menisci. Ninety-seven (57.8%) meniscal cysts were associated with meniscal tears. Of the total number of meniscal cysts, 104 (62.3%) had a parameniscal cyst. An isolated intrameniscal cyst was present in 63 (37.7%) cases. One hundred (96%) of the parameniscal cyst components were isointense to fluid on T2-weighted FSE images. All cysts exhibited abnormal intrameniscal signal. Only 14 (8.4%) of the intrameniscal components were isointense to fluid on T2-weighted FSE images. The arthroscopic reports of 88 of the 161 (54.7%) patients were available for review and correlation. A tear extending to the articular surface of the meniscus was reported to be present in 74 of the 88 (84%) arthroscopic examinations. Knowledge of the spectrum of findings and the relative frequency of various MR imaging characteristics as well as common potential pitfalls is important to the accurate diagnosis and management of mensical cysts. In particular, controversy exists as to the incidence of articular surface tears in association with meniscal cysts, with some authors reporting greater than 98% correlation with tears. Only 58% of cysts were associated with an articular surface tear. Ninety six percent of the parameniscal signal was isointense to fluid, only 8% of the intramensical signal was isointense to fluid.

Retears of postoperative knee meniscus: findings on magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) by using low and high field magnets

The purpose of this study was to determine the diagnostic performance of magnetic resonance (MR) obtained with intra-articular contrast medium in the evaluation of recurrent meniscal tears using low-field extremity-only and high-field whole-body magnets. Postoperative standard MR examinations and MR arthrographies of 95 knees were reviewed. Patients experiencing pain and disability after meniscal repair underwent standard MR and MR arthrography (Gadoterate meglumine 0.0025 mmol/ml) on both a 0.2-T and 1.5-T magnet. In 52 of 95 patients, second-look arthroscopy was performed; in the remaining 43 of 95 patients, clinical follow-up was used as the standard of reference. Sensitivity, specificity, positive and negative predictive values as well as accuracy of MRI/MR arthrographic signs as meniscal morphologic changes and the presence of contrast medium tracking into the tear at T1- and T2-weighted sequences in the detection of recurrent meniscal tears were determined. All MR and MR arthrograpic signs were sensitive in the detection of recurrent tears (range 80-91%). Abnormal meniscal morphology had low specificity [26% (13/50)] for both the 0.2-T and 1.5-T scanner, whereas accuracy was 55% (52/95) and 57% (54/95), respectively. The presence of contrast medium within the meniscus substance on T2-weighted images had higher value of specificity [84% (42/50)] and accuracy [84% (80/95)] by using low field strength magnet than by using high field strength magnet [74% (37/50) and 81% (77/95), respectively]. Whereas, the increased intrameniscal signal intensity extending to the meniscal surface at T1-weighted sequences after intra-articular contrast medium administration had lower specificity and accuracy on 0.2-T images [84% (42/50) and 82% (78/95), respectively] than on 1.5-T images [90% (45/50) and 88% (84/95), respectively]. A diagnosis of recurrent meniscal tear in a previously arthroscopically repaired meniscus can be made both on 0.2-T and 1.5-T magnets on the basis of increased signal on T2-weighted and T1-weighted images in the presence of intra-articular contrast material.

Paper #27 Dynamic MR perfusion imaging assessment of meniscal repair

The MR imaging assessment of the postoperative meniscus following meniscal repair is complicated by persistent surfacing intrameniscal signal intensity on short echo-time images, a classic MR imaging criterion of a primary meniscal tear, which may be seen at the site of a meniscal repair despite histologic and arthroscopic evidence of healing.

Lesions of the Menisci of the Knee

This study aimed to determine the value of four MR imaging criteria for evaluating unstable meniscal lesions. Criteria for unstable meniscal lesions were the presence of a displaced meniscal fragment, visibility on more than three 3-mm-thick coronal and two 4-mm-thick sagittal images, having more than one orientation plane or more than one pattern (contour irregularity, peripheral separation, tear), and having intrameniscal high signal intensity on T2-weighted spin-echo images. Sensitivity, specificity, and positive and negative predictive values for recognition of instability among all meniscal lesions were determined for the presence of each individual criterion and for the presence of at least one criterion in 50 consecutive patients (mean age, 46 years) who underwent MR imaging and subsequent arthroscopy. Sensitivities and specificities of these four criteria ranged between 18% and 54% and between 94% and 100%, respectively. Positive and negative predictive values ranged between 92% and 100% and between 39% and 52%, respectively. The presence of at least one criterion enabled recognition of unstable lesions with a sensitivity and specificity of 82% and with positive and negative predictive values of 90% and 70%, respectively. The four MR imaging criteria have high specificities and positive predictive values and low sensitivities and negative predictive values when evaluating unstable meniscal lesions.

Magnetic Resonance Imaging

Musculoskeletal SystemMRI is widely used to assist in the diagnosis of joint injuries, bone marrow disorders, soft-tissue tumors, and other musculoskeletal abnormalities. Fibrocartilage and ligaments normally appear dark because of a paucity of mobile protons61. In the knee, MRI has a reported sensitivity of 75 to 100 percent for the identification of meniscal tears, as indicated by an increased signal intensity in the fibrocartilaginous meniscus that extends to an articular surface (Figure 6A). MRI has largely supplanted arthrography62,63. Meniscal degeneration not seen at arthroscopy is detected as an increase in intrameniscal signal intensity; this finding is . . .

Knees of trained long-distance runners

A previous report indicated that recreational runners had increased meniscal signal intensity and visible joint effusions on magnetic resonance (MR) images after jogging. Therefore, the knees of trained long-distance runners were evaluated by means of MR imaging before and after competition to determine the presence of any structural alterations, particularly changes in intrameniscal signal intensity and/or joint effusions. T1-weighted coronal, proton-density and T2-weighted sagittal, and short T1 inversion recovery sagittal images were obtained in five trained runners 24 hours before and within 24 hours after completion of a long-distance race (distance range, 17-50 miles). Pre- and postrace images were filmed and windowed with standardized techniques. All ligaments were normal before and after the race. No alteration in meniscal signal intensity was noted for any menisci, and there was no increase in joint fluid after running. These data indicate that the knees of trained long-distance runners do not de...

Knees of trained long-distance runners: MR imaging before and after competition.

A previous report indicated that recreational runners had increased meniscal signal intensity and visible joint effusions on magnetic resonance (MR) images after jogging. Therefore, the knees of trained long-distance runners were evaluated by means of MR imaging before and after competition to determine the presence of any structural alterations, particularly changes in intrameniscal signal intensity and/or joint effusions. T1-weighted coronal, proton-density and T2-weighted sagittal, and short T1 inversion recovery sagittal images were obtained in five trained runners 24 hours before and within 24 hours after completion of a long-distance race (distance range, 17-50 miles). Pre- and postrace images were filmed and windowed with standardized techniques. All ligaments were normal before and after the race. No alteration in meniscal signal intensity was noted for any menisci, and there was no increase in joint fluid after running. These data indicate that the knees of trained long-distance runners do not demonstrate changes similar to those found in recreational runners, suggesting that these athletes may have adapted to the stresses of their activity.