Because of congenital abnormal collagenous structures and peripheral attachments, discoid lateral meniscus (DLM) is often associated with tears and instability and a risk of premature compartmental articular degeneration. Typically, surgery is indicated for symptomatic patients. Several surgical techniques have been described in the literature, but no studies have examined surgeon variation.

To determine the intersurgeon agreement for DLM surgical planning and postoperative restriction after arthroscopic assessment.

Cross-sectional study.

Sixteen orthopaedic surgeons from an international pediatric meniscus study group were shown 4 different videos of a DLM arthroscopic procedure. Each surgeon completed a survey for each arthroscopic video. The survey included questions about operative planning, such as peripheral rim preservation, repair and stabilization technique, and postoperative restrictions. Descriptive statistics were used to characterize the variables collected.

One of the 4 arthroscopic videos showed a complete discoid meniscus with no instability or tearing. For this specific meniscus, consensus was generally good, with 87.5% to 93.8% agreement for all the categories, except peripheral rim preservation, with 31.3% agreement. However, for the other 3 videos with tears and/or instability, consensus was generally low. Depending on the categories, the highest percentage of intersurgeon agreement varied between 25.0% and 62.5%, while being >50% only 2 of 27 times.

Agreement regarding the surgical technique and postoperative rehabilitation among surgeons with experience in the treatment of DLM is poor in the event of tears and instability, which represent the greatest technical challenges with the most significant functional effect. Given the relative rarity of the condition and the implications on a child's long-term joint health, prospective, comparative multicenter studies regarding treatment algorithms and outcomes are warranted.

The abnormal morphology of complete discoid lateral meniscus (CDLM) is associated with a greater propensity for tears. The magnetic resonance imaging (MRI) morphology of CDLM is most often described in the coronal plane, with few morphological studies in the sagittal position.

The sagittal anteroposterior diameter of CDLM is smaller than that of normal meniscus and is increased after tear in adults.

Cross-sectional study; Level of evidence, 3.

The authors searched the radiology records at our institution from June 2018 to December 2023 for patients aged from 18 to 55 years with knee pain. According to inclusion and exclusion criteria, 70 knees (66 patients) with torn CDLM were enrolled as group A, 36 knees (31 patients) with intact CDLM were enrolled as group B, and 48 knees (32 patients) with normal lateral meniscus (LM) were enrolled as group C. The coronal view passing through the middle point of the lateral tibial plateau (LTP) were identified the referrence coronal view, then the sagittal view passing through the middle point of the LTP on the referrence coronal view were selected for the measurements, the anterior distance, posterior distance, and anteroposterior diameter of the LM, sagittal tibial diameter (TD) were measured. The 4 measurements and the ratios were compared among the groups by independent sample t test.

The reliability of all measurements was excellent, except that posterior distance was classified as good in group B. The anteroposterior diameter and TD were smaller in group A than in group C (both P < .001) and smaller in group B than in group C (P < .001 and P = .007). anteroposterior diameter and anteroposterior diameter/TD in group A were larger than in group B (P = .003 and P < .001), while anteroposterior diameter/TD in group A and group C were similar (P > .05). The anterior distance and anterior distance/TD were smaller in group A than in group B (P = .02 and P = .03) and smaller in group A than in group C (P < .001 and P = .008). Posterior distance, posterior distance/anteroposterior diameter, and posterior distance/TD were larger in group A than in group C (P < .001, P < .001, and P < .001) and larger in group B than in group C (P < .001, P < .001, and P < .001).

Our study demonstrates that in adults, the meniscal anteroposterior diameter and the TD are smaller in CDLM than in normal LM, and the anteroposterior diameter of torn CDLM is larger than intact CDLM.

A discoid lateral meniscus (DLM) is the most common meniscus variant and is commonly treated with arthroscopic saucerization. There are mixed data regarding long-term results after surgery, especially in terms of radiological parameters.

The aim was to evaluate the functional and radiological results of patients who underwent arthroscopic saucerization for a symptomatic DLM. It was hypothesized that successful outcomes can be achieved by avoiding excessive resection while reshaping only to an extent that prevents mechanical symptoms.

Case series; Level of evidence, 4.

This study retrospectively analyzed pediatric and adult patients who had a symptomatic discoid meniscus between 2000 and 2018, who underwent arthroscopic saucerization with at least 10 mm of peripheral length, and who had at least 5 years of follow-up. Radiological parameters were measured on both preoperative and follow-up radiographs. Patient-reported outcome measure scores were recorded at follow-up.

The study included 57 knees of 53 patients (mean age, 27.6 years [range, 6-65 years]). The mean follow-up duration was 12.1 years (range, 5.0-23.1 years). There were 31 knees in the pediatric group and 26 knees in the adult group. No significant difference was found between the groups or between preoperative and follow-up values for the femorotibial angle (P > .05). When the preoperative and follow-up Kellgren-Lawrence grades were compared, no change was observed in the pediatric group (P = .125), while grades were shown to progress in the adult group (P < .001). The mean Lysholm score was 94.61 ± 7.61 and 84.23 ± 14.90 for the pediatric and adult groups, respectively (P = .001). Overall, 2 patients underwent arthroscopic surgery because of a symptomatic recurrence of symptoms, and 2 patients underwent arthroplasty because of osteoarthritis. The 10-year survival rate was 90.6%.

Limited saucerization of a DLM helped to preserve coronal-plane knee joint alignment. Functional and radiological results were superior in the pediatric patients. Even when alignment was more varus in older patients, preoperative and follow-up femorotibial angles were not statistically significant. This outcome may be used to guide treatment in appropriately selected cases.

Meniscal saucerization combined with repair of a symptomatic discoid lateral meniscus (DLM) has been expanding. However, the significance of meniscal saucerization with repair involving complex or degenerative tears remains uncertain.

The purpose of this study was to assess the radiological and clinical outcomes of saucerization with repair performed for symptomatic DLM tears in children and adolescents in comparison with a historical control cohort undergoing subtotal meniscectomy. It was hypothesized that saucerization with repair would lead to superior outcomes compared with subtotal meniscectomy.

Cohort study; Level of evidence, 3.

This study group consisted of 27 knees in 21 patients who underwent saucerization with repair (SR group) between 2011 and 2018, while the historical control group included 22 knees in 20 patients who underwent subtotal meniscectomy (SM group) between 2005 and 2011. Patient age at the time of surgery ranged from 4 to 18 years (mean, 12.1 years). Clinical outcomes were assessed using the Lysholm score. The Tapper and Hoover classification based on Rosenberg view radiographs was adopted, and lateral joint space width was measured as a parameter for cartilage/meniscus preservation. Clinical and radiological results were evaluated preoperatively, 2 years postsurgery, and until the final follow-up.

The mean follow-up period was 50.6 ± 17.0 months in the SR group and 62.3 ± 41.0 months in the SM group. Lysholm scores significantly improved postoperatively in both groups (P < .001). As for radiological evaluation, a progression in the Tapper and Hoover classification grade and a significant increase in lateral joint space width (P < .001) between the right and left sides were observed in both groups at 2 years postoperatively, with no significant differences between groups. Complications included postoperative retearing in 5 cases (18.5%) from the SR group, and osteochondritis dissecans (OCD) developed after surgery in 1 knee (4%) in the SR group and 6 knees in the SM group (27%), with a significantly higher incidence in the SM group (P = .036).

Both groups showed progressive postoperative radiographic degeneration, and clinical outcomes also improved in both groups. Based on the incidence of OCD development, saucerization with repair for complex DLM tears showed advantages over subtotal meniscectomy.

The meniscus plays an important role in absorbing shock, sharing load, reducing contact stress, and maintaining stability of knee joint movement. We know that there are various ways to repair meniscus injuries under arthroscopy. However, we found some technical limitations during the operation, such as the risk of neurovascular injury and the long operation time of repair. On this basis, we modified the lateral meniscus suture technique. A special technique of lateral meniscus repairs using a single posteromedial portal by all-inside suture is proposed: from posterior to anterior, we believe that this technique can effectively optimize the surgical procedure and reduce the time of repair surgery resulting from angle problems, and the use of this method can effectively reduce the possibility of damage to the nerves, blood vessels, and tendons in the knee joint. Surgeons who are initially exposed to arthroscopic repair of the lateral meniscus can use this repair method, which reduces the surgical threshold for the suture of the lateral meniscus.

A discoid meniscus is a morphological abnormality wherein the meniscus loses its normal 'C' shape. Although most patients are asymptomatic, patients might still present with symptoms such as locking, pain, swelling, or giving way. Magnetic resonance imaging is usually needed for confirmation of diagnosis. Based on a constellation of factors, including clinical and radiological, different approaches are chosen for the management of discoid meniscus. The purpose of this review is to outline the treatment of discoid meniscus, starting from conservative approach, to the different surgical options for this condition. The PubMed and Google Scholar databases were used for this review. Studies discussing the treatment of discoid meniscus from 2018 to 2023 were searched. Initially there were 369 studies retrieved, and after removal of studies using the exclusion criteria, 26 studies were included in this review. Factors such as stability, presence of tear, and morphology can help with surgical planning. Many approaches have been used to treat discoid meniscus, where the choice is tailored for each patient individually. Postoperatively, factors that may positively impact patient outcomes include male sex, body mass index < 18.5, age at symptom onset < 25 years, and duration of symptoms < 24 months. The conventional approach is partial meniscectomy with or without repair; however, recently, there has been an increased emphasis on discoid-preserving techniques such as meniscoplasty, meniscopexy, and meniscal allograft transplantation.

This study aimed to evaluate the meniscal size of asymptomatic discoid lateral meniscus (DLM) and compare it with that of normal lateral meniscus (LM) and to compare changes in meniscal dimensions with age among patients with asymptomatic DLM and those with normal LM using magnetic resonance imaging (MRI).

We retrospectively reviewed the medical records, including MRI data, of patients with asymptomatic DLM (DLM group) or normal LM (control group). Width and extrusion of both DLM and normal LM and tibial length were measured and compared using mid-coronal and mid-sagittal MR images. Meniscal size and sagittal and coronal meniscal ratio according to age, as well as differences between DLM and normal menisci, were also evaluated.

Thirty-four knees were included in the DLM group, whereas the control group comprised of 50 patients. The DLM group showed significantly less meniscal extrusion, greater coronal width, posterior capsule distance, sagittal meniscal length, and sagittal meniscal ratio than the control group (DLM: 0.1 ± 0.3 mm, 23.3 ± 2.2 mm, 5.4 ± 2.4 mm, 25.1 ± 2.8 mm, 61 ± 6%, and control: 0.4 ± 0.4 mm, 9.5 ± 2.3 mm, 2.5 ± 1.2 mm, 30.2 ± 2.6 mm, 71 ± 4%, respectively). The coronal meniscal ratio decreased with age in both the control (p = 0.001) and DLM (p = 0.037) groups. The sagittal meniscal ratio (p = 0.001) and minimum height (p = 0.04) decreased and the anterior capsule distance (p = 0.035), posterior capsule distance (p = 0.026), and entire sagittal length (p = 0.005) increased with age in the DLM group, while the distance between the meniscal inner margins (p = 0.019) increased with age in the control group.

The meniscal ratio in the sagittal plane of the DLM group was significantly lower than that of the control group. The sagittal meniscal ratio of asymptomatic DLM decreased with age, indicating that the size of asymptomatic DLM does not change with age.

III: Retrospective comparative study.

This study evaluated the differences in meniscal sizes and occupancy between symptomatic and asymptomatic patients diagnosed with discoid lateral meniscus (DLM) using magnetic resonance imaging (MRI) to understand how these variations relate to the presence of symptoms and the patients' age.

A retrospective review of 98 patients with DLM was conducted, excluding those with meniscal displacement. Both the width and extrusion of DLM and the percentage of the meniscus to the tibia were measured using mid-coronal and mid-sagittal MRI and compared between symptomatic and asymptomatic DLM groups. The relationships among each parameter, meniscal size, and patient age were evaluated. Symptomatic cases were divided into those with and without horizontal tears on MRI to compare the differences in meniscal morphology.

A total of 92 knees from 74 patients were included. Sixty-one knees required surgical intervention for symptomatic DLM, while 31 were asymptomatic and included the contralateral side of symptomatic knees. The symptomatic group exhibited larger morphological variations than the asymptomatic group. Moreover, the sagittal meniscal ratio reduced with age in the asymptomatic group (r = - 0.54, p = 0.002) but remained constant in the symptomatic group. The symptomatic cases with horizontal tears demonstrated larger meniscal dimensions and smaller posterior capsule distances than those without tears.

Symptomatic patients with DLM had larger knee morphological changes than asymptomatic ones. Age affected the meniscal occupancy in the sagittal plane only in asymptomatic patients.

III.

A discoid lateral meniscus (DLM) is more prone to tear, and treatment of this condition is challenging. The purpose of the present study was to investigate (1) whether a torn DLM is associated with more varus alignment than a torn semilunar lateral meniscus (SLM) and (2) whether the lower-limb alignment associated with a torn DLM changes with age.

Consecutive patients who underwent arthroscopic knee surgery for a torn lateral meniscus were included. Patients with a torn DLM (confirmed on arthroscopy) were allocated to the DLM group; those with a torn SLM were allocated to the SLM group. After strict screening according to the inclusion and exclusion criteria, 436 and 423 patients were included in the DLM and SLM groups, respectively. The mechanical axis deviation (MAD), hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle, and medial proximal tibial angle were compared between the 2 groups after propensity score matching. Additionally, the correlation of the HKA and MAD with age was evaluated within the DLM group.

After propensity score matching, all baseline characteristics were well balanced between the 2 groups. The DLM group had significantly more varus alignment than the SLM group (MAD: 3.6 mm ± 9.6 mm versus 1.1 mm ± 10.3 mm, respectively, p = 0.001; HKA: 179.1° ± 2.9° versus 179.9° ± 3.0°, respectively, p = 0.001). Within the DLM group, the MAD (R = 0.10, p = 0.032) and HKA (R = -0.13, p = 0.007) had a weak correlation with age.

Patients with a torn DLM had more varus knee alignment than those with a torn SLM, and this trend did not increase with age after minimizing the effects of osteoarthritis. Therefore, surgical treatment may not be appropriate for asymptomatic DLM.

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Partial meniscectomy is commonly performed for symptomatic patients with discoid lateral meniscus (DLM) if conservative treatment fails. However, the development of knee osteoarthritis and osteochondral lesion are detrimental postoperative complications. This study aimed to evaluate the effect of the volume of resected DLM on the contact stress of the tibiofemoral joint using a finite element analysis.

Subject-specific finite-element models of the knee joint of a patient with DLM were developed from computed tomographic and magnetic resonance images. To evaluate the effect of partial meniscectomy on the contact stress in the lateral tibiofemoral joint, six knee models were created in the study (the native DLM, and five partially meniscectomized DLMs (according to the preserved width of the meniscus: 12 mm, 10 mm, 8 mm, 6 mm, and 4 mm)).

As the volume of resected DLM increased, higher contact stress was applied to the lateral tibiofemoral joint. Greater contact stress was applied to the preserved lateral meniscus than to the native DLM.

From a biomechanical viewpoint, the native DLM was the most protective against lateral tibiofemoral contact stress in comparison to partially meniscectomized DLMs.

Discoid lateral meniscus (DLM) is an anatomic knee variant associated with increased tears and degeneration. This study aimed to quantify meniscal status with magnetic resonance imaging (MRI) T2 mapping before and after arthroscopic reshaping surgery for DLM.

We retrospectively reviewed the records of patients undergoing arthroscopic reshaping surgery for symptomatic DLM with ≥ 2-year follow-up. MRI T2 mapping was performed preoperatively and at 12 and 24 months postoperatively. T2 relaxation times of the anterior and posterior horns of both menisci and of the adjacent cartilage were assessed.

Thirty-six knees from 32 patients were included. The mean age at surgery was 13.7 years (range 7-24), and the mean follow-up duration was 31.0 months. Saucerization alone was performed on five knees and saucerization with repair on 31 knees. Preoperatively, the T2 relaxation time of the anterior horn of the lateral meniscus was significantly longer than that of the medial meniscus (P < 0.01). T2 relaxation time significantly decreased at 12 and 24 months postoperatively (P < 0.01). Assessments of the posterior horn were comparable. The T2 relaxation time was significantly longer in the tear versus non-tear side at each time point (P < 0.01). There were significant correlations between the T2 relaxation time of the meniscus and that of the corresponding area of the lateral femoral condyle cartilage (anterior horn: r = 0.504, P = 0.002; posterior horn: r = 0.365, P = 0.029).

The T2 relaxation time of symptomatic DLM was significantly longer than that of the medial meniscus preoperatively, and it decreased 24 months after arthroscopic reshaping surgery. The meniscal T2 relaxation time of the tear side was significantly longer than that of the non-tear side. There were significant correlations between the cartilage and meniscal T2 relaxation times at 24 months after surgery.

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 ± 1.1 mm, asymptomatic DLM: 0.1 ± 0.4 mm, and normal LM: 0.3 ± 0.6 mm, 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.

Discoid lateral meniscus (DLM) presents with differing pathoanatomy and may exhibit various types of tears. The treatment strategy is based on the presence and location of instability as a result of deficient capsular attachment. Recently, meniscal stabilization after saucerization has been recommended for DLM to preserve the meniscus shape, prevent extrusion, and mitigate against the progression of osteoarthritis. In addition to stabilization, the resection volume is important to prevent osteoarthritic changes. Although there was no tear and no displacement of the lateral meniscus on magnetic resonance imaging, some DLMs were found to have tears and peripheral instability during arthroscopy. Therefore, the assessment of peripheral instability during surgery is very important to achieve a desirable clinical outcome. This Technical Note describes an arthroscopic technique for anterior peripheral stabilization of the DLM, in which we highlight the surgical procedure for repair of the anterior horn, reassess the instability around the popliteal hiatus after the anterior horn is repaired, and the stabilization of the posterior horn, if necessary.