Bilateral occurrence and morphologic analysis of complete discoid lateral meniscus

Discoid lateral meniscus: current concepts

The discoid meniscus is a congenital morphological abnormality encountered far more commonly on the lateral than the medial side. The discoid lateral meniscus (DLM) is more prevalent in Asia with an incidence of 10%-13%, than in the Western world with an incidence of 3%-5%. DLM can be bilateral in more than 80% cases. Due to its abnormal shape and size, the discoid meniscus is prone to tearing and has an impact on gait mechanics. The discoid meniscus has deranged collagen arrangement and vascularity which can have implications for healing after a repair. Patients with a DLM may or may not be symptomatic with mechanical complaints of locking, clicking, snapping or pain. Symptoms often arise due to a tear in the body of the meniscus or a peripheral detachment. Asymptomatic patients usually do not require any treatment, while symptomatic patients who do not have locking are managed conservatively. When a peripheral detachment is present, it must be stabilised while preserving the meniscus rim to allow transmission of hoop stresses. Rehabilitation after surgery is highly individualised and return to sports is possible after more than 4 months in those undergoing a repair. The functional outcomes and onset of radiographic arthritis after saucerisation and repairing a discoid meniscus are better in the long term, compared with a subtotal meniscectomy. However, there is no compelling evidence currently favouring a repair as results deteriorate with increasing follow-up. Poor prognosis is reported in patients undergoing a total meniscectomy, a higher age at presentation and valgus malalignment.

Factors associated with bilateral discoid lateral meniscus tear in patients with symptomatic discoid lateral meniscus tear using MRI and X-ray

BACKGROUND

The incidence of bilateral discoid lateral meniscus (DLM) is as high as 73 to 85%, and associated contralateral meniscus tears ranged from 4 to 33% in symptomatic surgical DLM. The goal of the study was analyzing the factors that predict contralateral presence and tearing of DLM in patients who underwent surgery for symptomatic DLM. Our hypothesis was that there is a significant correlation between operative DLM properties and the incidence of bilateral DLM with associated contralateral meniscus tears. These properties include tear patterns, younger patient age, and characteristic X-ray findings.

PATIENTS AND METHODS

This prospective study included 76 patients who underwent arthroscopic surgery for symptomatic DLM. The contralateral knees were evaluated with X-ray and MRI. Based on the MRI findings, DLM was categorized into three types, and tear patterns were analyzed. The characteristic X-ray findings were evaluated as follows: (1) high fibular head, (2) squared-off appearance of the lateral femoral condyle, (3) cupping of the lateral tibial plateau, (4) widened femorotibial joint space, (5) hypoplasia of the lateral intercondylar spine, (6) notching of the LFC. The number of characteristic X-ray findings (0/1/more than 2) was noted. Binary logistic analysis was performed to find the factors that predict the presence and tear of contralateral DLM.

RESULTS

MRI of contralateral knees revealed 43 cases (57%) of complete DLM, 25 cases (33%) of incomplete DLM, and 8 cases (11%) of normal meniscus. Meniscus tears were found in 29 cases (38%) in the contralateral knee. X-ray of the contralateral knee revealed that 27 patients (36%) had one and 24 patients (32%) had two or more characteristic X-ray findings. On logistic regression analysis, the associations between contralateral knee meniscal tear and the presence of one or more than two characteristic X-ray findings were statistically significant (OR: 16.5, p=0.028; OR: 264.0, p=0.000, respectively).

DISCUSSION

The number of characteristic X-ray findings in the contralateral knee is a significant predictive factor for contralateral DLM type and/or tear. Symptomatic DLM patients with characteristic X-ray findings should be carefully evaluated for contralateral DLM and meniscal tears.

LEVEL OF EVIDENCE

III, prospective diagnostic study of consecutive patients.

The Fate of the Contralateral Knee in Patients With a Lateral Discoid Meniscus

PURPOSE

To analyze the survivorship of the lateral meniscus (LM) in the contralateral knee after surgery for symptomatic torn discoid lateral meniscus (DLM) and to determine its associated factors.

METHODS

Two hundred ninety-six patients who underwent arthroscopic meniscectomy for torn symptomatic DLM were reviewed retrospectively. Patients were classified into subgroups based on demographic, clinical, and radiologic variables. The survivorship analysis of the LM on the contralateral knee was calculated using the Kaplan-Meier method, and comparison among the subgroups was conducted using the log-rank test. The predicted prognostic factors associated with survivorship were determined using Cox proportional hazard regression analysis.

RESULTS

Of the 296 patients, 51 (17%) had arthroscopic surgery in the contralateral knee during the study period. The group ≥40 years old had significantly worse survival than the group <40 (log-rank test, P < .001). In terms of radiologic variables, the group with Kellgren-Lawrence grade 3 or 4 had significantly poorer survivorship than that with grade 1 or 2 (log-rank test, P = .045). Age ≥40 years was associated with poorer survivorship (hazard ratio, 3.235; 95% confidence interval, 1.782-5.875; P < .001). Kellgren-Lawrence grades 3 and 4 in the contralateral knee were associated with poorer survival (hazard ratio, 2.071; 95% confidence interval, 1.061-4.043; P = .033). The cumulative survival rate at 10 years of the LM in the contralateral knee after surgery for symptomatic torn DLM was 81%.

CONCLUSIONS

Patients with a lateral discoid meniscus have a risk of a similar condition in the contralateral knee. Increased risks of symptomatology are associated with age and degenerative changes.

LEVEL OF EVIDENCE

Level IV, retrospective uncontrolled case series.

Editorial Commentary: Why Should the Contralateral Side Be Examined in Patients With Symptomatic Discoid Lateral Meniscus?

Recent reports have found the rate of bilateral discoid lateral meniscus (DLM) to be high (79%-97%) in patients with unilaterally symptomatic DLM; the associated torn meniscus incidence is also high at 33%. The present study results indicated that older, symptomatic DLM patients with more degenerative changes may be at risk for a similar condition in the contralateral knee. Long-term follow-up with magnetic resonance imaging screening for asymptomatic contralateral knees is necessary to determine the fate of the contralateral knee.

Symptomatic discoid lateral meniscus: a clinical and arthroscopic study in a Chinese population

BACKGROUND

Discoid lateral meniscus (DLM) is relatively common in East Asia..Symptomatic discoid lateral meniscus (SDLM) is an important indication for knee arthroscopic surgery. However, studies investigating SDLM are rare. The purpose of this study was to evaluate the clinical characteristics and intra-articular variants of SDLM in a Chinese population.

METHODS

We retrospectively reviewed all patients with SDLM from January 2005 to December 2014 in our hospital. Clinical variables included gender, age, duration, age of onset, affected side, symptoms and trauma history as well as arthroscopic findings: DLM types, tear patterns and concomitant medial meniscus tear, which were evaluated and compared statistically.

RESULTS

Of the 496 consecutive participants with SDLM, females outnumbered males (69.6 % vs. 30.4 %). The age of onset ranged from 3 to 80 years (median, 31 years), and was significantly higher in females than in males (p < 0.0001). Trauma history in males was significantly higher than in females (45 % vs. 35.1 %, p = 0.0356). Males showed a higher incidence of popping and snapping, while females manifested higher range-of-motion (ROM) limitations (p = 0.0179, and p = 0.0392, respectively). No significant difference in intra-articular variants was observed between genders. The complete type was the most frequent (344, 69.4 %), followed by the incomplete type (149, 30 %), and the Wrisberg type (3, 0.6 %). Significant difference in tear patterns was found between complete and incomplete types (p < 0.0001). Few patients showed medial meniscus tear (11, 2.2 %), at a significantly higher age compared with patients without tear (median, 57 years vs. 33 years, p < 0.0001).

CONCLUSIONS

The majority of Chinese patients with SDLM are young and middle-aged females. Female patients had an older age of onset, higher incidence of ROM limitation and limited trauma history. The complete type is the most common, with tear patterns varying between complete and incomplete types. The SDLM does not significantly affect the medial meniscus.

Three-dimensional knee kinematics in patients with a discoid lateral meniscus during gait

BACKGROUND

To date, the knee kinematics of a discoid lateral meniscus (DLM) has not been elucidated. The aim was to investigate the three-dimensional knee kinematics in knees with a DLM using gait analysis.

METHODS

Ten patients (mean: 14years) diagnosed with bilateral DLM and unilaterally symptomatic snapping as well as 10 healthy controls (mean: 23years) participated in the study. Each patient with a DLM had unilaterally snapping knee in full extension and deep flexion. The three-dimensional gait analysis was performed with the point cluster technique. All subjects were asked to walk on a level floor at the speed of their choice. In the sagittal plane, knee excursion was separately evaluated during the weight acceptance phase and the mid-stance phase. In the axial plane, knee excursion during the stance phase was assessed. Finally, knee excursion during the whole gait cycle was evaluated in the frontal plane. Statistical comparison was conducted between groups, and between both sides in the DLM group.

RESULTS

In the sagittal plane, knee excursions during the weight acceptance phase and the mid-stance phase were significantly smaller in the DLM group than in the control group; in addition, these were smaller on the symptomatic side than on the asymptomatic side in the DLM group. In the axial plane, knee excursion was also significantly smaller on the symptomatic side than on the asymptomatic side in the DLM group, whereas the frontal knee motion did not differ significantly.

CONCLUSION

Less knee motion in the sagittal plane may prevent snapping during extension and flexion in patients with a DLM.

LEVEL OF EVIDENCE

III.