discoid meniscus is a well - documented knee pathology , and there are many cases of medial or lateral discoid meniscus reported in the literature .
however , ipsilateral concurrent medial and lateral discoid meniscus is very rare , and only a few cases have been reported .
a 27-year - old japanese man complained of pain on medial joint space in his right knee that was diagnosed as a complete medial and lateral discoid meniscus . in magnetic resonance imaging , although the lateral discoid meniscus had no tear , the medial discoid meniscus had a horizontal tear .
arthroscopic examination of his right knee similarly revealed that the medial discoid meniscus had a horizontal tear .
in addition , the discoid medial meniscus also had an anomalous insertion to the anterior cruciate ligament , and there was also mild fibrillation of the medial tibial cartilage surface .
we performed arthroscopic partial meniscectomy for the torn medial discoid meniscus but not for the asymptomatic lateral discoid meniscus .
we report a rare case of ipsilateral medial and lateral discoid meniscus with medial meniscus tear .
the medial discoid meniscus with tear was treated with partial meniscectomy , whereas the lateral discoid meniscus without tear was only followed up .
discoid meniscus is not only at peripheral attachments of the tibial plateau but it is also at the central sites . it is reported that discoid meniscus causes meniscus tear due to poor blood flow at the central sites , direct compression , and an unstable connection with posterior capsule . according to previous reports , discoid lateral meniscus is sometimes observed , but concurrent ipsilateral medial and lateral discoid meniscus is rare [ 1 , 2 ] .
we report a case of concurrent ipsilateral medial and lateral discoid meniscus with medial meniscus tear .
a 27-year - old male patient complained of pain on medial joint space in his right knee after running on the road for few years .
he subsequently consulted a nearby clinic and was diagnosed with medial and lateral discoid meniscus in his right knee with medial meniscus tear on magnetic resonance imaging ( mri ) .
physical findings for his right knee showed that although the range of motion was not limited , there were swelling and pain on the medial joint space .
in addition , the mcmurray test revealed pain and clicking on the medial joint line with external rotation .
. t2-weighted coronal and sagittal mri of his right knee revealed medial and lateral complete discoid meniscus , which was confirmed by arthroscopic examination of his right knee .
the medial meniscus had a complete discoid conformation with a horizontal tear , whereas the lateral meniscus had no tear ( fig .
arthroscopic examination of his right knee similarly revealed that the lateral discoid meniscus had no tear , and the medial discoid meniscus had a horizontal tear .
in addition , the discoid medial meniscus also had an anomalous insertion to the anterior cruciate ligament , and there was also mild fibrillation of the medial tibial cartilage surface ( fig .
2 ) . t2-weighted coronal and sagittal magnetic resonance imaging ( mri ) of his right knee .
( a ) at lateral side , the lateral meniscus had a complete discoid conformation without tear .
hence , we did not perform surgery , ( b and c ) at medial side , the medial meniscus had a complete discoid conformation with a horizontal tear , ( d ) we performed arthroscopic partial meniscectomy of the medial discoid meniscus .
we performed no surgical procedure for the lateral discoid meniscus because the patient had no clinical symptoms , and the lateral discoid meniscus had no tear .
we also checked the stability of the connection between the meniscus and the posterior soft tissue both medially and laterally ( fig .
three months later , the patient had no pain or symptoms in his right knee and resumed playing sports . at the last follow - up , 18-month post - surgery ,
he had no limitation of motion , could play sports with full effort , and was satisfied with the result .
the medial joint space in his right knee was observed clearly on mri , and the lateral meniscus had no tear ( fig .
the medial joint space was observed clearly , and the lateral meniscus had no tear .
yaniv and blumberg   and ikeuchi   reported that lateral discoid meniscus is more common in asian countries than in other countries .
the reported incident of discoid meniscus ranges from 0.4% to 17% for the lateral [ 1 , 3 , 4 ] , 0.06 - 0.3% for the medial , and < 0.012% for the medial and lateral in same knee .
the incidence of bilateral lateral discoid meniscus is up to 20% of the lateral discoid meniscus cases , whereas bilateral medial meniscus ranges from 0.01% to 0.03% [ 5 , 6 ] .
however , cases of ipsilateral concurrent medial and lateral discoid meniscus are rare . to the best of our knowledge ,
only five cases have been reported [ 4 , 5 , 7 , 8 ] .
although the developmental formation process of the normal meniscus is unclear , the normal meniscus is clearly defined at the 8 week of gestation and assumes mature anatomical shape at the 14 week .
smillie   reported that in many cases , the fetal meniscus has an oval shape and covers the central zone of the tibial plateau .
the shape of a normal meniscus is the result of gradual absorption of the central zone by stimulation of the knee joint during the latter half of fetal life .
differences in the occurrence rate of the error result in differences in the incidence rate between medial and lateral discoid meniscus . recently ,
fukazawa et al .   reported a difference in collagen deposits between the medial and lateral meniscus during fetal life .
histology of the meniscus in human fetuses , at the 14 week of gestation , showed spindle - shaped cells aligned in parallel in the lateral meniscus but randomly arranged cells in the medial meniscus .
collagen deposits formed wavy bundles - like structure in the lateral meniscus , whereas those in the medial meniscus were distributed relatively randomly . it was suggested that the strength of the medial meniscus is weaker than that of the medial meniscus in human fetuses . in response to this report , yujiro et al .   suggested that the medial meniscus likely forms due to absorption of the central zone as the result of kinematic load at the knee joint ; therefore , medial discoid meniscus is not likely to occur because of the difference in collagen deposits between the medial and lateral meniscus .
however , we did not investigate collagen deposits in the current case , so further studies are needed to confirm this .
the treatment of discoid meniscus is controversial . in adults , many discoid meniscus cases , both medial and lateral ,
early surgery is important when symptoms are clear . because total meniscectomy has a high risk of osteoarthritis , partial meniscectomy or meniscoplasty should be performed . in younger patients ,
it is best to perform auxiliary meniscorrhaphy whenever possible . in a case of lateral discoid meniscus in a child under 8 years old , stilli et al
.   reported that subtotal meniscectomies are preferable when the meniscal tissue is degenerated as some adaptation of the knee to stress activity may occur . in children
reported clinical results of four cases of medial discoid meniscus and showed that meniscoplasty provided satisfactory but imperfect results in all cases while avoiding total meniscectomy .
they also reported that residual pain and knee snapping may persist after treatment ; thus , careful follow - up is needed . both kim and lubis   and choi et al .  
reported clinical results of ipsilateral concurrent medial and lateral discoid meniscus , the same as the present case .
they performed arthroscopic partial meniscectomy for the torn discoid meniscus and no surgical procedure for the asymptomatic discoid meniscus , reporting good clinical results for each case .
our patient also had no complaints and has been satisfied with the result of his surgery .
however , a longer follow - up period is needed because discoid meniscus and partial meniscectomy have been reported as risk factors for articular cartilage lesions , so we will continue to follow the patient for a long time .
we report a rare case of ipsilateral concurrent medial and lateral discoid meniscus with a medial meniscus tear .
we performed arthroscopic partial meniscectomy for his torn medial discoid meniscus and no surgical procedure for the asymptomatic lateral discoid meniscus . for 18-month post - surgery
, the patient has had no limitation of the motion and is satisfied with the result .
although medial or ipsilateral medial and lateral discoid are rare cases , we should know this presence .
if there is torn discoid meniscus , we should perform arthroscopic partial meniscectomy . however , if there is asymptomatic discoid meniscus without tear , we should continue long time follow - up .
 introduction : discoid meniscus is a well - documented knee pathology , and there are many cases of medial or lateral discoid meniscus reported in the literature . 
 however , ipsilateral concurrent medial and lateral discoid meniscus is very rare , and only a few cases have been reported . herein , we report a case of concurrent medial and lateral discoid meniscus.case report : a 27-year - old japanese man complained of pain on medial joint space in his right knee that was diagnosed as a complete medial and lateral discoid meniscus . in magnetic resonance imaging , although the lateral discoid meniscus had no tear , the medial discoid meniscus had a horizontal tear . 
 arthroscopic examination of his right knee similarly revealed that the medial discoid meniscus had a horizontal tear . 
 in addition , the discoid medial meniscus also had an anomalous insertion to the anterior cruciate ligament , and there was also mild fibrillation of the medial tibial cartilage surface . 
 we performed arthroscopic partial meniscectomy for the torn medial discoid meniscus but not for the asymptomatic lateral discoid meniscus . 
 the latest follow - up at 18 months indicated satisfactory results.conclusion:we report a rare case of ipsilateral medial and lateral discoid meniscus with medial meniscus tear . 
 the medial discoid meniscus with tear was treated with partial meniscectomy , whereas the lateral discoid meniscus without tear was only followed up . 
Introduction:
Case Report:
Conclusion:
Introduction
Case Report
Discussion
Conclusion