Symptomatic discoid lateral meniscus shows a relationship between types and tear patterns, and between causes of clinical symptom onset and the age distribution

Abstract

Purpose Discoid meniscus is a congenital abnormality of the lateral meniscus and is seen more frequently in East Asia. The purpose of this study was to retrospectively assess the relationship between discoid lateral meniscus (DLM) types and tear patterns and causes of age-speciic clinical symptom onset. Methods Of 1650 arthroscopic surgeries over a 20-year period, 138 (105 patients) were performed for DLM and were evaluated in this study. The mean age at surgery was 21.5 ± 15.8 years. The DLM type was classiied by Watanabe's classiication, and tear patterns were classiied by the modiied Bin's classiication as simple horizontal, complicated horizontal, longitudinal, radial, complex, and no tear. Additionally, patients were divided by age group (< 10, 10-19, 20-39, 40-59, and ≥ 60 years) and classiied according to the causes of clinical symptom onset as follows: sports activities, minor trauma in daily living, and no traumatic episode. ResultsThe DLM was complete in 78 (56.5%) knees and incomplete in 60 (43.5%); no Wrisberg type DLM was observed. Simple horizontal and complicated horizontal tears were signiicantly more frequent in complete DLM, whereas radial tears and no tears were signiicantly more frequent in incomplete DLM (p < 0.0001). When classiied by age group, 74 (53.6%) knees with DLMs were found in teenagers. Sports activities caused symptom onset signiicantly more often in teenagers, no traumatic episode caused symptom onset in patients aged < 10 years, and minor trauma in daily living caused symptom onset in patients aged 40-59 years and ≥ 60 years (p < 0.0001). No relationship was found between the age distribution and tear patterns; however, the absence of tears tended to be more common in teenaged patients, and complicated horizontal tears were more common in patients over 20 years of age. Conclusion Symptomatic DLM occurred most often in teenagers. A relationship was identiied between the DLM types and tear patterns, which could be helpful in preoperative planning. Causes of clinical symptom onset in patients with DLM were characterised by age group, which might help clinicians to suspect the presence of DLM. Level of evidence Level IV.

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

“…D iscoid medial meniscus is an extremely rare anomaly with an estimated incidence of 0.03% to 0.3% [8][9][10][11] , and this case represents the third discoid medial meniscus completely coalesced with ACL. Different speculations and hypotheses about the etiology of discoid meniscus have been explained but not yet been completely ascertained [11][12][13][14] .…”

Arthroscopic Saucerization and Repair of the Lateral Discoid Meniscus

“…23 The discoid lateral meniscus has a higher risk of injury to the meniscus compared to the normal meniscus and are innately different between the complete and incomplete types both histologically and biologically. 65 The complete discoid lateral menisci are also more likely to have associated tears compared to incomplete discoid lateral menisci 19 and are more likely to have a horizontal tear configuration, compared to the incomplete discoid lateral menisci where higher frequencies of radial tears have been reported. 2,19,20 Surgeons should thus be vigilant in the inspection for associated tears in the complete discoid lateral meniscus, which may not be apparent until after saucerization, especially in the small pediatric knee.…”

“…14 Favorable outcomes have been shown in degenerative horizontal meniscal tear repairs, 15,16,17 and peripheral meniscus instability can be concurrently addressed with the same repair techniques by anchoring the meniscus to the joint capsule. 18 As tears are commonly associated with the discoid lateral meniscus, 2,19,20 especially in the degenerative horizontal cleavage configuration, 21,22 meniscal repair should be performed in conjunction with saucerization to create a functional meniscus for improved shock absorption and load transmission.…”

“…35,36 The hypermobility of the discoid meniscus can cause pain and mechanical symptoms in younger children and is more likely to result in tears in adolescents. 1,25,30,[37][38][39] The symptoms from the discoid lateral meniscus occur most frequently in teenagers and are often caused by sports activity 19 and are associated with meniscus tears. 30 In the younger pediatric population, these symptoms are often not associated with any trauma.…”

“…30 In the younger pediatric population, these symptoms are often not associated with any trauma. 19 Snapping in the knee with discoid meniscus classically occurs between ages of 5 and 10 years. 30 In the younger child (3 to 4 years old), snapping may not be associated with pain.…”