Review Question - QID 212140

This patient's history of acute on chronic knee pain, physical examination, and description of his plain radiographs are suggestive of a symptomatic discoid lateral meniscus due to a lateral meniscus tear.

While plain radiographs are often normal in children with discoid menisci, severe discoid menisci may reveal squaring of the lateral femoral condyle, cupping of the lateral tibial plateau, and widening of the lateral joint line. As such, MRI of the knee has been demonstrated to be the most sensitive for identifying discoid menisci and usually reveals contiguous central meniscus on three consecutive slices. Though most children with discoid menisci are asymptomatic, some may present with pain that is largely secondary to an underlying meniscal tear. Initial treatment of chronic asymptomatic discoid menisci is nonoperative, 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 have good short-term efficacy in cases of symptomatic discoid menisci.

Incorrect Answers:
Answer 1: The flattening and cupping of the lateral femoral condyle and tibial plateau, respectively, are suggestive of a discoid lateral meniscus (not a popliteus tendon injury, which would reveal instability in flexion).
Answer 2: ALL injuries have been associated with ACL tears, not discoid menisci.
Answer 3: Physical examination would demonstrate varus instability if there was a grade 3 fibular collateral ligament injury.
Answer 4: Physical examination would demonstrate instability and a positive Dial test if the posterolateral corner was injured.