A discoid meniscus is a developmental anomaly - something that just happens in some people who are born with a meniscus more like a flat round disc than a C-shaped wedge.
There may be no symptoms, and cause a surgeon some confusion when he peers into the joint and sees this unusual structure. Quite often, though, discoid menisci may be symptomatic, the symptoms commonly beginning in childhood -
A discoid meniscus can tear like any other meniscus and cause locking and joint line pain.
Surgery for a symptomatic discoid meniscus usually involves trimming it to approximately the shape of a normal meniscus.
If MRI investigation reveals a discoid meniscus but it is not causing problems then the surgeon may decide not to do anything about it until or unless there is a problem.