Review Question - QID 212118

This 13-year-old girl's history, examination, and imaging findings (squaring of lateral femoral condyle and cupping of tibial plateau) are suggestive of a discoid lateral meniscus. Discoid menisci are caused by failure of apoptosis during in-utero development.

Discoid menisci often presents as snapping or clicking in the knee, but most children are usually asymptomatic. Less frequently, children may present with pain that is largely secondary to an underlying meniscal tear. MRI of the knee has been demonstrated to be the most sensitive for identifying discoid menisci. The presence of a contiguous central meniscus on three consecutive 5 mm slices is usually indicative of the diagnosis. Treatment is usually focused on conservative modalities, with surgical intervention reserved for symptomatic cases with recurrent locking, swelling or persistent pain.

Kramer et al. reviewed the diagnosis and treatment of meniscal tears and discoid meniscus in children. They reported that discoid menisci represent a spectrum of morphologic abnormalities and instability of the lateral meniscus, most commonly. They highlighted that highly unstable variants often present with the classic snapping knee syndrome, while stable variants may remain asymptomatic until a tear develops. They recommended that asymptomatic discoid menisci should be observed, and that symptomatic types be treated with saucerization and repair.

Good et al. reviewed the operative results of children and young adults treated arthroscopically for symptomatic discoid lateral menisci. They reported that arthroscopic saucerization was successful in 28 of 30 knees, with 2 cases (large complex tears precluding meniscal salvage) requiring complete arthroscopic meniscectomy. They concluded that arthroscopic saucerization and repair has good short-term efficacy in cases of symptomatic discoid menisci.

Figure A depicts a knee AP radiograph with squaring of the lateral femoral condyle and cupping of lateral tibial plateau. Figure B depicts five 5mm sagittal images with meniscal continuity, classic for discoid menisci.

Incorrect Answers:
Answer 1: This refers to osteochondritis dissecans of the knee, which is not present in this patient.
Answer 2: The COL5A1 gene is associated with increased risk of ACL ruptures (not discoid menisci) in females.
Answer 4 and 5: While these have been demonstrated to have direct effects on ACL injuries, this has not been the case for discoid menisci.