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Background: A discoid medial meniscus is rare in comparison with a discoid lateral meniscus. We encountered a new type of incomplete discoid with an oversized posterior segment. Therefore, this study aimed to report cases of medial meniscus with an oversized posterior segment and analyze the morphological characteristics by comparing them to cases with a discoid medial meniscus and normal medial meniscus. Methods: Four patients with an oversized posterior segment medial meniscus (oversize group, mean age: 25.3 ± 12.0 years) and seven patients with a discoid medial meniscus (discoid group, mean age: 34.4 ± 19.6) were identified using magnetic resonance imaging (MRI) and diagnosed by arthroscopic findings in our hospital. Fifty patients without medial meniscal injury were retrospectively selected as the normal group (normal group, mean age: 24.0 ± 11.3 years). The clinical symptoms were examined. The anteroposterior (AP) length of both the anterior and posterior segments, AP length ratio of the posterior segment to the AP length of the medial tibial plateau, and mediolateral (ML) width of the mid-body of the medial meniscus were also evaluated using MRI and compared among the three groups. Results: All patients in the oversize group complained of medial knee pain during deep knee flexion. In sagittal MRI, posteriorly deviated indentations were also observed at the medial tibial plateau in all cases in the oversize group. There was a significant difference in the AP length of the posterior segment between the normal and oversize groups (14.3 ± 2.8 vs. 23.6 ± 2.8 mm, P < 0.001), whereas there was no significant difference in the AP length of the anterior segment (9.1 ± 2.1 vs. 9.5 ± 1.9 mm, P = 0.869). The ML width of the mid-body in the normal, oversize, and discoid groups was 9.3 ± 1.8, 19.9 ± 2.6, and 25.8 ± 1.9 mm, respectively (normal vs. oversize group: P < 0.001, oversize vs discoid group: P = 0.01, normal vs. discoid group: P < 0.001). Conclusions: Oversized posterior and normal anterior segments characterize this new type of incomplete discoid medial meniscus as a morphological abnormality. [ABSTRACT FROM AUTHOR]

Discoid menisci on both the medial and lateral sides are rare, and there are very few reports on cases involving both sides. We report a case of a 52-year-old female with medial and lateral discoid menisci in both knees. Arthroscopy revealed the lateral menisci of both knees were complete discoid menisci, and partial meniscectomy was performed. The medial menisci were incomplete discoid menisci, but there were no findings of abnormal mobility or injury; therefore, the medial menisci were observed without treatment. At six months postoperatively, her pain and range of motion restrictions disappeared. [ABSTRACT FROM AUTHOR]

Purpose: To introduce and evaluate the clinical results of a new arthroscopic technique for partial meniscectomy of symptomatic lateral discoid meniscus using a knife. Materials and Methods: From March 2005 to October 2010, 60 knees of 58 patients underwent arthroscopic partial meniscectomies for lateral discoid meniscus. The average age was 28.9 years (range, 12 to 63 years), and average follow-up was 26 months (range, 8 to 72 years). In this procedure, using a No. 11 knife holder inserted through the high far anteromedial portal, a stab incision on the anterior meniscal horn and following piecemeal meniscal excision were made. Clinical results were assessed using the scale of Ikeuchi and Lysholm score. Results: Meniscus shape was complete in 32 knees (53.3%) and incomplete in 28 knees (46.6%). The shape of tears in complete type lesions was horizontal cleavage in 17 knees (53.1%), flap or complex degenerated tears in 10 knees (31.2%) and radial tears in 5 knees (15.6%). Clinical results assessed using the scale of Ikeuchi were excellent in 38 (63.3%), good in 13 (21.6%), fair in 8 (13.3%) and poor in 1 knee (1.6%). The average Lysholm score was improved from 82.8 preoperatively to 95.4 postoperatively. Conclusions: Our new arthroscopic technique in lateral discoid partial meniscectomy suggests convenient methods and successful clinical results. [ABSTRACT FROM AUTHOR]