Arthroscopic one-piece reshaping for symptomatic discoid medial meniscus with anomalous amalgamating into anterior cruciate ligament

Discoid shapes of lateral menisci are relatively common finding, whereas discoid medial menisci are less common. Discoid medial meniscus with associated anomalous variants has been reported. However, symptomatic complex tear of complete type discoid medial meniscus with anomalous blending with anterior cruciate ligament is an extremely rare pathology. A 35-year-old male was admitted to our hospital with left knee pain and loss of terminal extension for 2 years. On physical examination, the patient presented with clicking and restriction during the extension motion of the knee joint. Magnetic resonance imaging and arthroscopy indicated complex tear of complete discoid medial meniscus in association with anomalous connection between entire apical portion of discoid medial meniscus and tibial insertion portion of the anterior cruciate ligament. We obtained a successful outcome with arthroscopic resection and shaping in one-piece method using no. 11 scalpel blade.     

Symptomatic Complete Discoid Medial Meniscus Completely Coalesced with the Anterior Cruciate Ligament: A Case Report and Literature Review

BackgroundComplete discoid medial meniscus is an extremely rare abnormality of the knee joint whose meniscus has a discoid shape rather than a normal semilunar one. Several medial meniscus anomalies including anomalous insertion have been reported in the literature. This report presents a rare case of symptomatic complete discoid medial meniscus whose anterolateral (apical) portion was completely coalesced with the ACL. MRI, radiographic, and arthroscopic findings in the medial compartment are to be submitted.Case PresentationA 29‐year‐old male presented with intermittent pain and swelling of the right knee for 2 years. Based on radiographic, MRI, and physical examination findings, he was diagnosed with discoid medial meniscus tears. Arthroscopic saucerization was performed for the torn discoid medial meniscus of the right knee. Arthroscopic examination revealed a complete discoid medial meniscus and the anterolateral (apical) portion of which was completely coalesced with the ACL. Careful Probing of the meniscal surface revealed there was a longitudinal tear extending from the tibial spine to the midportion of the meniscus. Arthroscopic saucerization of the discoid meniscus was performed after closely cutting the meniscus around the ACL. The patient reported no symptoms, and he had returned to his daily and sports activities, including football, basketball, and jogging, at the 12‐month follow‐up.ConclusionComplete discoid medial meniscus is an extremely rare abnormality, and this case presents the third complete discoid medial meniscus whose anterolateral (apical) portion was completely coalesced with the ACL. The current case we present strongly supports the hypothesis that ACL and meniscus were differentiated from the same mesenchyme.     

Discoid medial meniscus

A discoid medial meniscus is an extremely rare anomaly. We present 4 cases of symptomatic discoid medial meniscus. Furthermore, magnetic resonance imaging (MRI) of the unaffected knee was obtained in 3 cases, and 1 patient had bilateral discoid medial menisci as well as a unilateral discoid lateral meniscus proven by MRI. Another patient had bilateral discoid medial menisci. In one of the other 2 cases, an MRI of the unaffected knee was not obtained. However, in the involved knees of both cases, medial and lateral menisci were discoid. The incidence of bilateral discoid medial menisci is unknown. In the past, the diagnosis of a discoid meniscus was made with an arthrogram or at arthrotomy. Therefore, whether some of the unilateral cases reported in the literature might have been bilateral is unknown. The reported prevalence of bilateral discoid medial menisci will probably increase, because when a discoid medial meniscus is encountered currently, an MRI is used to find knee disorders, including in the contralateral knee. Axial multiplanar gradient-recalled-echo imaging could provide images of the discoid meniscus, depicted in its entirety in one section. This would make the recognition of a discoid meniscus simple.     

Anomalous insertion of the medial menisci

Many types of meniscal anomalies have been reported. The authors encountered two cases of anomalous insertion of the anterior horn of the medial menisci to the lateral femoral condyle, which ran up along the course of the anterior cruciate ligament (ACL), but was independent of the ACL. These anomalies were noted during arthroscopic examination and surgery of the ipsilateral knee for a torn discoid meniscus and a patellar fracture. A 34-year-old woman had a horizontal tear of the lateral discoid meniscus. We performed arthroscopic partial meniscectomy of the inner torn portion of the lateral discoid meniscus and contoured it to resemble a normal meniscus. An anomalous insertion of the medial meniscus was found on examination of the joint during surgery. A 32-year-old man had a patellar fracture and we performed reduction under arthroscopy and internal fixation with cannulated screws. The same anomalous insertion of the medial meniscus was also found on examination of the joint during surgery. We report the cases with a review of the literature.Arthroscopy 1998 Jul-Aug;14(5):505-7     

Bilateral discoid lateral menisci and unilateral discoid medial menisci

Discoid lateral meniscus is a well-studied and documented entity of the knee whereas discoid medial meniscus is an extremely rare pathology. There are no more than 25 cases of medial discoid menisci reported in the literature. Some articles report bilateral lateral menisci as well as bilateral medial menisci, but there are no publications about medial and lateral discoid menisci in the same knee with lateral discoid meniscus in the contralateral side. This is a report of a case of bilateral discoid lateral menisci and unilateral discoid medial meniscus. Both arthroscopy and magnetic resonance imaging views are presented.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 7 (September), 2001: pp 772–775     

Irreducible open posterolateral knee dislocation due to medial meniscus interposition

Posterolateral knee dislocations are generally irreducible due to the interposition of the medial capsule and retinaculum. These injuries have a 'dimple sign' which shows the invagination of the tissues in the medial joint line. We present an unusual case of an open posterolateral traumatic knee dislocation (KD-4 [ACL/PCL/MCL/LCL-PLC torn] open knee dislocation) without a 'dimple sign'. Closed reduction attempts were unsuccessful. In surgery, it was found that the medial meniscus was detached from the meniscocapsular junction and entrapped in the joint. The medial meniscus was extracted from the joint, and the joint was reduced. The medial meniscus was sutured to the meniscocapsular junction with anchors. This is the first study reporting medial meniscus interposition in an open posterolateral knee dislocation. Moreover, the presented case is peculiar because although it was a posterolateral knee dislocation, the posterolateral ligament complex was also torn.     

Discoid lateral meniscus in a young child: case report and review of the literature

Management of discoid lateral meniscus in a 6-month-old child is discussed. The patient presented with a lateral knee mass and an associated popping sound of the joint during flexion and extension. The diagnosis, which the authors believe to be the youngest presentation of this entity, was confirmed by arthrography. Computed tomographic features and magnetic resonance images of the discoid meniscus are presented. Management and theories of etiology of the discoid lateral meniscus are discussed.     

Medial discoid meniscus with cyst formation in a child

A medial discoid meniscus with cystic formation was found in a 9-year-old girl. The cyst was located in the anterolateral part of the meniscus, mechanically blocking knee extension. The presenting symptom was knee flexion contracture. Total meniscectomy was followed by full recovery.     

Meniscal allograft transplantation for symptomatic knee after meniscectomy of torn discoid medial meniscus: Report of three cases

In symptomatic discoid medial meniscus, partial meniscectomy is the principal treatment method and can yield promising short-term results. However, unlike the nondiscoid meniscus, discoid medial meniscus is frequently associated with horizontal cleavage tears, attributable to the presence of myxoid degeneration in the intrameniscal substance, in that it may potentially occur deteriorating long-term results because of re-tearing of remaining meniscus or secondary degeneration of cartilage of the medial compartment after meniscectomy. We experienced three rare cases of retear or secondary degeneration of cartilage of the medial compartment after meniscectomy for two patients with torn bilateral meniscus. Both patients were highly active young males. Meniscal allograft transplantation in complicated discoid medial meniscus was performed. At 2 years after meniscal allograft transplantation, clinical outcomes were improved with a normal range of motion. Orthopedic surgeons should recommend activity modification to prevent possible complicated injury of the discoid medial meniscus. Meniscal allograft transplantation may be an alternative option in highly active young patients undergoing complicated discoid medial meniscus to diminish pain, improve knee function, and prevent or delay degeneration.     

Bilateral complete discoid medial menisci combined with anomalous insertion and cyst formation

A female student had a complete discoid medial meniscus of right knee combined with a meniscal cyst and anomalous insertion to the anterior cruciate ligament. This was confirmed by magnetic resonance imaging (MRI) and the arthroscopic procedure. Also shown by the MRI, the left knee had the discoid medial meniscus, but it was asymptomatic.     

关节镜下诊治膝内侧盘状半月板4例

目的 :探讨关节镜下诊治的4例膝内侧盘状半月板的临床特点。方法 :自2012年4月至2015年5月,采用关节镜诊治膝关节内侧盘状半月板4例(4膝),其中男1例,女3例;年龄7~56岁,平均26岁。4例患者均在关节镜下行半月板成形术,观察术后症状体征并采用Lysholm膝关节评分进行疗效评价。结果:4例患者均获得随访,时间6~20个月,平均12个月。末次随访时患膝Lysholm评分为83.5±10.0,其中优2膝,良1膝,中1膝。结论:膝内侧盘状半月板早期临床症状不典型,容易漏诊,常因半月板撕裂产生明显症状而就诊,确诊后宜尽早手术,半月板成形术疗效良好。     

Bilateral complete discoid medial meniscus: a case report

Discoid medial meniscus is very rare, and bilateral discoid medial meniscus is extremely rare. We report a case of bilateral discoid medial meniscus. The patient had symptoms in the right knee but was asymptomatic in the left knee. We performed magnetic resonance imaging for both knees. The patient was treated by saucerization and by all inside repair of the anterior horn tear in the right knee. We performed second-look arthroscopy after 18 months.     

Anomalies of the discoid medial meniscus

Anomalies associated with a discoid medial meniscus have been described. However, the clinical relevance of these anomalies has not been previously reported. Therefore, we report the clinical relevance of some of these anomalies based on our experience with a 21-year-old soldier with a 3-month history of medial right knee pain. Magnetic resonance imaging (MRI) revealed bilateral discoid medial menisci, cupping of the medial tibial plateau, and an abnormal anteroinferior transposition of the anterior horn of the meniscus. Partial meniscectomy was performed in the usual manner and the meniscus reshaped, including its anteromedial corner.     

Analysis of the discoid meniscus in Koreans.

Discoid meniscus is a relatively common disorder of the knee in Koreans. Its arthroscopic treatment is one of the most technically demanding procedures of this field. The purposes of this study were to define the clinical features of the discoid meniscus in Koreans and to suggest an adequate arthroscopic technique. We performed arthroscopic meniscectomy on 37 knees with a lateral discoid meniscus. The average length of follow up was 21 months. The presence of synovial hypertrophy in the knee with discoid was significantly higher than that with a non-discoid meniscal lesion. A medial midpatellar portal for the arthroscope is advisable for clean arthroscopic surgery in this situation. We obtained satisfactory results through the partial resection of the discoid meniscus, leaving the normal semilunar-shaped meniscus intact as much as possible.     

应用关节镜治疗膝关节盘状半月板的疗效分析

目的探讨关节镜下手术治疗膝关节盘状半月板损伤的疗效。方法对本院骨科在2006年1月～2009年6月收治23例膝关节外侧盘状半月板损伤在关节镜下手术进行回顾性分析。根据盘状半月板损伤情况分别施行半月板全切除术和次全切除术11例,部分切除7例和半月板成形术5例。手术前和手术后6个月均采用Lysholm评分对膝关节功能进行评分。结果本组病人术后未发生切口感染,关节内感染,明显的关节积血,血管神经损伤和下肢静脉血栓形成等并发症。术后活得随访21例,随访时间8～28个月,平均13.2个月。所有患者术后膝关节疼痛及肿胀症状消失或明显减轻,关节活动恢复正常。手术前Lysholm评分为52～92分,平均为69.2分,手术后6个月提高至79～92分,平均为86.6分。手术前后Lysholm评分具有显著性差异(P<0.01)。结论关节镜技术治疗膝关节外侧盘状半月板具有损伤创伤小、手术时间短、术后恢复快等优点,是作为临床治疗膝关节盘状半月板的首选术式。     

Importance of the medial meniscus in the anterior cruciate ligament-deficient knee.

The incidence of meniscal tears in the chronically anterior cruciate ligament-deficient knee is increased, particularly in the medial meniscus because it performs an important function in limiting knee motion. We evaluated the role of the medial meniscus in stabilizing the anterior cruciate ligament-deficient knee and hypothesized that the resultant force in the meniscus is significantly elevated in the anterior cruciate ligament-deficient knee. To test this hypothesis, we employed a robotic/universal force-moment sensor testing system to determine the increase in the resultant force in the human medial meniscus in response to an anterior tibial load following transection of the anterior cruciate ligament. We also measured changes in the kinematics of the knee in multiple degrees of freedom following medial meniscectomy in the anterior cruciate ligament-deficient knee. In response to a 134-N anterior tibial load, the resultant force in the medial meniscus of the anterior cruciate ligament-deficient knee increased significantly compared with that in the meniscus of the intact knee; it increased by a minimum of 10.1 N (52%) at full knee extension to a maximum of 50.2 N (197%) at 60 degrees of flexion. Medial meniscectomy in the anterior cruciate ligament-deficient knee also caused a significant increase in anterior tibial translation in response to the anterior tibial load, ranging from an increase of 2.2 mm at full knee extension to 5.8 mm at 60 degrees of flexion. Conversely, coupled internal tibial rotation in response to the load decreased significantly, ranging from a decrease of 2.5 degrees at 15 degrees of knee flexion to 4.7 degrees at 60 degrees of flexion. Our data confirm the hypothesis that the resultant force in the medial meniscus is significantly greater in the anterior cruciate ligament-deficient knee than in the intact knee when the knee is subjected to anterior tibial loads. This indicates that the demand on the medial meniscus in resisting anterior tibial loads is increased in the anterior cruciate ligament-deficient knee compared with in the intact knee, suggesting a mechanism for the increased incidence of medial meniscal tears observed in chronically anterior cruciate ligament-deficient patients. The large changes in kinematics due to medial meniscectomy in the anterior cruciate ligament-deficient knee confirm the important role of the medial meniscus in controlling knee stability. These findings suggest that the reduction of resultant force in the meniscus may be a further motive for reconstructing the anterior cruciate ligament, with the goal of preserving meniscal integrity.     

Discoid lateral meniscus in children: limited knee extension and meniscal instability in the posterior segment

BACKGROUND: Limited knee extension is a well-known sign in children with discoid meniscus, but its causative mechanism is controversial. The purpose of this study was to characterize discoid meniscus with this clinical manifestation with a focus on instability of the posterior segment and its morphologic features. METHODS: The authors retrospectively reviewed magnetic resonance imaging and intraoperative arthroscopic videos of 34 knees in 32 consecutive patients (age range, 4.5-15.0 years) who underwent arthroscopic treatment for symptomatic discoid lateral meniscus. Knees were classified into 2 groups, depending on the presence (n = 19) or absence (n = 15) of an extension block, which was defined as a limitation of knee extension by 10 degrees or more under general anesthesia. Meniscal instability in the posterior segment was determined based on arthroscopic findings, and its correlation with knee extension block was analyzed. Using magnetic resonance imaging, the thicknesses of anterior and posterior segments were measured to assess significance of the thickness differences by a presence of knee extension block and by the posterior segment instability. RESULTS: There were 13 knees with a stable posterior segment and 21 knees with an unstable posterior segment. Meniscal instability in the posterior segment was observed in the knees with a surface tear (n = 12), in a hypermobile posterior rim despite the absence of a surface tear (n = 5), and in knees with a freely movable posterior rim without posterior tibial attachment (n = 4). Knee extension block occurred exclusively in complete type menisci and was significantly correlated with meniscal instability in the posterior segment. Magnetic resonance imaging observations suggested that morphologic features characteristic of thick anterior and thin posterior segments were significantly associated with meniscal instability in the posterior segment. Clinically, knee extension block disappeared in all cases within 4 months of arthroscopic treatment. CONCLUSIONS: A redundant anterior segment associated with meniscal instability in the posterior segment is likely to cause limited knee extension in children with discoid lateral meniscus. This correlation mandates that discoid menisci be thoroughly evaluated during arthroscopic treatment to identify any instability that might require stabilization.     

Medial and lateral discoid meniscus in the same knee

To our knowledge, only 1 case of medial and lateral discoid meniscus in the same knee has been reported. We report on 2 cases of medial and lateral discoid meniscus in the same knee.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 2 (February), 2001: pp E9–E9     

Discoid lateral meniscus in children: clinical manifestations and morphology.

The authors investigated the correlation between the clinical manifestations and the morphology of discoid lateral meniscus. Thirty-eight children, age 5 to 17 years, with 39 cases of discoid lateral meniscus underwent an arthroscopic procedure and magnetic resonance imaging. The two most frequent preoperative clinical manifestations were pain and extension block. In 19 cases without surface tear, the most frequent clinical manifestation was extension block. In the sagittal magnetic resonance images, the mean thickness of the anterior portion of the discoid lateral meniscus (7.77 mm) in the group with extension block exceeded that (4.02 mm) in the group without extension block. Extension block was significantly more common in patients with the anterior hypertrophy type and the slab (anterior-posterior diffusely hypertrophic) type than in the posterior hypertrophy type by the modified Hall classification. As a result, extension block was significantly correlated with the morphology of the menisci. Also, the thickened anterior portion of the discoid lateral meniscus may be considered one of the mechanical factors that limit knee extension.     

Radiographic knee dimensions in discoid lateral meniscus: comparison with normal control.

We reviewed the knee radiographs of 68 cases of arthroscopically proven discoid lateral meniscus, including 42 cases of complete type and 26 cases of incomplete type discoid lateral meniscus. Knee radiographs of 70 cases that had no arthroscopic evidence of pathology of the meniscus were used as controls. We excluded patients who had significant trauma history and who were under 16 years of age or over 60 years to avoid measuring radiographs of skeletally immature or degenerative knees. The absolute values and relative normalized values of specific knee dimensions, such as a squared-off appearance of the lateral femoral condyle, widened femorotibial joint space, cupping of the lateral tibial plateau, obliquity of the lateral tibial plateau articular surface, high fibular head, and hypoplasia of the lateral intercondylar spine, were compared between the patients with discoid lateral meniscus and the normal controls. Among those dimensions, high fibular head and widened lateral tibiofemoral joint space showed statistically significant differences between the discoid lateral meniscus group and normal control group. We suggest that these findings would be useful in screening lateral discoid meniscus on plain radiography.