MRI of discoid lateral meniscus]

We retrospectively reviewed the MR examinations of 10 patients (17 knees) with surgically documented discoid lateral meniscus of the knee joint. As MRI of the knee is being used more often, the criteria for diagnosis of this entity with MRI need to be established. We tried to define MRI criteria for the detection of discoid menisci by performing numerical measurements of MR images on a display screen. The transverse diameter of the midbody of a discoid lateral meniscus averaged 21.9 mm (normal control: 8.6 mm), and its proportion to the transverse width of the tibia averaged 29.4% (normal control: 12.0%). The measurable difference in height between the discoid and the medial meniscus was negligible. The number of sagittal sections on which the anterior and posterior horns connected varied from two to five in cases of discoid lateral meniscus, and from zero to two in normal controls. Among these parameters, the transverse diameter and its proportion of the transverse width of the tibia proved to be the most reliable. We concluded that a discoid meniscus is indicated if a transverse diameter of a lateral meniscus exceeds 15 mm (proportion to the tibia: 20%).     

Double-layered lateral meniscus

A case of double-layered lateral meniscus in which an accessory proximal hemimeniscus was overlying the body and posterior horn of the lateral meniscus is here reported. The accessory hemimeniscus lays marginal and parallel to the normal lateral meniscus with its periphery dissociated from the capsule and was significantly thinner and more mobile than its underlying counterpart. It was resected arthroscopically, and the patient’s symptoms were significantly improved. This case demonstrates an interesting and extremely rare anatomical abnormality of the lateral meniscus.     

Accessory lateral discoid meniscus

The lateral meniscus tends to have more developmental variation than the medial counterpart. This is a report of an accessory discoid layer of lateral meniscus. All arthroscopic, magnetic resonance imaging and histopathological views are presented.No financial support received from anybody or any commercial party.     

Symptomatic torn discoid lateral meniscus in adults

The purposes of this study were to report degenerative changes that coexist with a symptomatic torn discoid lateral meniscus in adults and to analyze the factors associated with the accompanied degenerative changes. From 1997 to 2008, 329 knees in the 305 patients were included. Associations between the status of the meniscus and the coexisting degenerative changes on the images and the arthroscopic findings were statistically analyzed. Marginal osteophyte was seen on conventional radiography in 118 patients (36%). Ninety patients (27%) had arthroscopically confirmed chondral lesion. Age, duration of symptoms, the type of meniscus, the type of tear and the magnetic resonance image classification were associated with the formation of the marginal osteophyte and chondral lesion on univariate analysis (P < 0.05). After conducting multivariate analysis, the type of tear and magnetic resonance image classification had a statistically significant association with the severity of marginal osteophyte and chondral lesion (P < 0.05).     

Displacing lateral meniscus masquerading as patella dislocation

Purpose

To alert the treating clinician to an uncommon knee meniscal condition that often masquerades as a more common patella condition.

Methods

Retrospective chart review of a series of cases was undertaken. A series of 12 knees in 11 patients were referred to an orthopaedic surgeon with a diagnosis of recurrent lateral patella dislocation. Three knees had undergone patella realignment surgery with continuance of symptoms. Eight patients had prior magnetic resonance images read as no meniscal pathology and no acute patella/patella retinacular injury. All patients presented for a consult with a similar history.

Results

Under anaesthesia, all knees had a stable patella as judged by physical examination. At the time of surgery, six patients had a frank tear in the lateral meniscus, all of which were readily displaceable. Six knees showed a displaceable lateral meniscus with attenuation but not a visible frank tear. Ten menisci were treated with repair, and two knees underwent partial lateral meniscectomies. Patient follow-up of minimally 18 months revealed no further episodes of “knee-cap dislocation” or symptoms of catching and locking.

Conclusions

The clinician treating a patient with a history of a knee locking in flexion should have a high index of suspicion for a lateral meniscus tear or an unstable hypermobile lateral meniscus, despite patient report of perceived patella movement. History of symptoms occurring in knee flexion and attention to patella physical examination should be key factors in this diagnostic conundrum.

Level of evidence

Retrospective chart review, Level IV.     

Arthroscopic thermal shrinkage for hypermobile lateral meniscus

BACKGROUND: The posterior segment of the lateral meniscus is relatively mobile as compared with that of the medial meniscus; that is because of its characteristic anatomy. Abnormal mobility of the lateral meniscus with no obvious rupture can be an unusual cause of knee pain and locking during deep knee flexion. PURPOSE: To evaluate results for a small series of patients with hypermobile lateral meniscus, treated with thermal shrinkage of the supporting ligaments. STUDY DESIGN: Series of case reports. METHOD: Five patients with hypermobile lateral meniscus were identified out of 625 patients who underwent meniscus surgery over a 20-month period. Thermal energy was applied to the peripheral zone of the lateral meniscus until abnormal translation was reduced. The patients were followed up an average of 21 months after the surgery. RESULTS: In 4 patients, no recurrence of locking was encountered in the postoperative period. In 1 patient, locking was experienced again 3 months after surgery and meniscal repair was performed. CONCLUSIONS: Thermal shrinkage can be considered an appropriate treatment in place of subtotal meniscectomy or meniscal repair for hypermobility of the lateral meniscus.     

MRI appearance of Wrisberg variant of discoid lateral meniscus

OBJECTIVE: A discoid lateral meniscus is a common normal variant, occurring in approximately 3-5% of the population. A subgroup of the discoid lateral meniscus known as the Wrisberg variant occurs when there is no posterior attachment of the lateral meniscus. Instead, Wrisberg's ligament becomes the only lateral meniscus posterior stabilizer, with a symptomatic hypermobile meniscus. Although it is commonly described in the orthopedics literature, to our knowledge the Wrisberg variant of the discoid lateral meniscus is not mentioned in the radiology literature. This article describes the MRI appearance of this important yet often unrecognized process. CONCLUSION: The Wrisberg variant of the discoid lateral meniscus is a rare condition with a highly suggestive clinical history. The musculoskeletal radiologist should consider this diagnosis whenever a discoid lateral meniscus is identified because making this elusive diagnosis may prove immensely useful for the orthopedic surgeon.     

Discoid lateral meniscus and the frequency of meniscal tears

Objective. To use MRI to determine the incidence of discoid lateral menisci in a large study population, and to compare those patients with those without a discoid meniscus in order to assess the impact of a discoid lateral meniscus on the frequency of meniscal tears. Design and patients. Results of 1250 knee MRI studies were retrospectively reviewed. Using the criterion of three or more meniscal body segments on sequential sagittal images, 56 patients were found to have a discoid lateral meniscus. After exclusion of patients with prior knee surgery, 49 patients with a discoid lateral meniscus were compared with 1146 patients without a discoid meniscus. Patients were categorized as having tears of the medial meniscus, lateral meniscus, or both menisci. Results. In our study population, there was a 4.5% incidence of discoid lateral meniscus. Seventy-one percent of patients with a discoid lateral meniscus had one or more meniscal tears, compared with 54% of the comparison group (P=0.01). The frequency of solitary lateral meniscal tears in the discoid group was also higher than in the comparison group: 20%.versus 11% (P=0.03). The frequency of solitary medial meniscal tears and concomitant tears of both menisci were not significantly different between the two groups. Conclusions. The discoid lateral meniscus is an uncommon variant, but not as rare as once believed. Compared with the normal semilunar meniscus, the discoid lateral meniscus has a higher frequency of meniscal tears, and solitary tears of the lateral meniscus are more common in the discoid variant. The frequency of medial meniscal tears is not altered by the presence of a discoid lateral meniscus. Received: 17 August 2000 Revision requested: 11 December 2000 Revision received: 15 January 2001 Accepted: 16 January 2001     

MR imaging of meniscal tears with discoid lateral meniscus

Objective: To study MR findings of meniscal tears with discoid lateral menisci (DLMs) and to evaluate the incidence and accuracy of MRI compared to arthroscopical surgery. Material and methods: MR appearances of surgically proved torn discoid lateral menisci (DLM) were studied in 57 knees (40 patients). They were all performed with a 1.5T MR before surgery. MR sequences included T1- and T2* weighted images on both coronal and sagittal planes and 3D-axial images with a slice thickness of 0.7 mm. Result: Of 57 DLMs, there were 32 complete DLMs and 25 incomplete DLMs. Twenty-five of 32 complete DLMs had tears; including seven with intrasubstance tear, five with radial tear, five with other kinds of tears and eight with severe tears involving whole meniscus. On the other hand, 13 of 25 incomplete DLMs had tears; including two with intrasubstance tear, six with radial tear, four with other kinds of tears and one with severe tears. All DLMs were correctly diagnosed on MR images. Twenty-seven of 38 tears with DLM were correctly identified on conventional 2D MR images. This yielded 71.1% sensitivity, 100% specificity and 80.7% overall accuracy. When adding axial 3D MR images to 2D MR images, 36 of 38 tears were correctly diagnosed. A combination of both techniques yielded a sensitivity of 94.7% and a specificity of 100%. Ten of 11 radial tears with DLM were correctly identified on 3D axial images, where only three of them could be diagnosed on conventional 2D images. Eight of nine intrasubstance tears were correctly identified on 3D axial images, where six of them could be diagnosed on conventional 2D images. Conclusion: DLMs had a much higher incidence of meniscal tears than normally shaped lateral menisci and MR is the only modality of choice to evaluate them before surgery. Especially 3D axial MR images were quite useful in the detection of intrasubstance and radial tears often associated with DLMs.     

Arthroscopic treatment for symptomatic discoid lateral meniscus during childhood

Purpose  

The purpose of this study was to review the operative long-term results of a large cohort of children treated arthroscopically for a symptomatic discoid lateral meniscus.     

Self-limited healing of a radial tear of the lateral meniscus

Radial tears of the meniscus have for decades been treated with partial meniscectomy. However, unstable radial tears usually involve the vascular zones where the circumferential collagen fibers are located. Therefore, in recent years, there has been a great strive to repair radial tears. To the author’s knowledge, this is the first case report of a self-limited healing of a radial tear of the lateral meniscus. The patient had a prior injury where he sustained a radial tear to his lateral meniscus and underwent a limited partial meniscectomy. A second-look arthroscopy was performed only after a second injury to the same knee occurred several months later, and it revealed that the radial tear of the lateral meniscus had spontaneously healed. The patient recovered well and returned to full athletic activities.     

Bilateral double-layered lateral meniscus: a report of two cases

Only a few cases of double-layered meniscus have been described in the English literature. We report two cases of bilateral double-layered lateral meniscus, where an additional semicircular meniscus was observed over the normal lateral meniscus. One of the patients exhibited a bucket-handle tear with a double-layered meniscus. To our knowledge, this abnormality is extremely rare and the incidence of double layered meniscus with bucket-handle tear has not been previously reported.     

Discoid lateral meniscus: diagnosis and results of arthroscopic treatment

We evaluated the results of arthroscopic meniscectomy in patients with discoid lateral menisci of the knee. Discoid lateral menisci were detected in 308 patients, of whom 197 (124 males, 73 females; mean age 34.5 years, range 6-67) were clinically, radiologically, and arthroscopically found to be symptomatic and underwent partial meniscectomy. The average period between injury and operation was 13.2 months (range 6-52). The results were evaluated according to the Ikeuchi and Lysholm criteria. The mean follow-up was 57.8 months (range 24-138). The most common complaints were pain (66%) and joint line tenderness (61%). Widening of lateral joint space was the most common radiological finding (25%). The confirmation of diagnosis by magnetic resonance imaging was not congruent with arthroscopic results for some patients (31%). According to the Ikeuchi criteria, the results were excellent in 110 patients (56%), good in 53 (27%), fair in 26 (13%), and poor in 8 (4%). On the other hand, according to the Lysholm scale, the results were excellent in 119 patients (60%), good in 57 patients (29%), fair in 16 (8%), and poor in five (3%) patients. Clinical and radiological findings were not congruent with arthroscopic results for all patients. Therefore arthroscopic evaluation has more value for discoid lateral meniscus. Moreover, tear pattern and degenerative changes in lateral compartment may effect outcomes without relation to the type of surgery. We concluded that arthroscopic partial meniscectomy should be the preferred method for the surgical treatment for discoid lateral menisci, due to it's minimal traumatic effects, possibilities of early mobilization, a lower complication rate, and easy and short rehabilitation period.     

Arthroscopic partial meniscectomy for horizontal tear of discoid lateral meniscus

A new method of arthroscopic partial meniscectomy for horizontal tear of discoid lateral meniscus was devised to preserve as much meniscal tissue as possible. To evaluate the clinical result of this method for horizontal tear of discoid lateral meniscus, 31 knees (30 patients) were reviewed at an average follow-up of 35 months (range 14-48 months). Horizontally torn discoid lateral menisci were classified as incomplete (11 cases) or complete (20 cases) by the Watanabe classification; no Wrisberg type was noted. Partial meniscectomy was performed in all cases. For the technique of a new method of partial meniscectomy, the unstable leaf of the horizontally torn meniscus was removed to the peripheral rim, but the stable one was preserved and reshaped to produce the similar appearance to the normal lateral meniscus in terms of width and thickness. It was trimmed to have a balanced rim of meniscal tissue about 6-8 mm in width. Meniscal repair was added to partial meniscectomy in one case. All the cases were rated using the Lysholm Knee Scoring Scale and were reviewed to recognize retear clinically. The scores increased after partial meniscectomy by average 20.7 (from 73.0 to 93.7). Recurrence of tear or aggravation of symptoms was not noted at the final follow-up.