P3.242: A 3-yr old with a limp who "kneeds" a diagnosis.

Introduction: A 3 year old female presented initially to a pediatric emergency room with acute onset of inability to weight bear on her left lower extremity for 1 1/2 days. Mom denies known trauma, swelling, bruising, erythema and no systemic symptoms.

Case Description: In the ED, exam demonstrated posterior knee tenderness, no effusion, unwilling to flex leg. Labs and X-rays pelvis, femur, and knee were unremarkable. Ibuprofen was given. Peds Orthopedics was consulted and after ibuprofen knee flexed to 115 degrees and child sent home with diagnosis of transient synovitis. 3 days later was seen in pediatric rheumatology and guarding found with flexion past 115-120 degrees but no swelling. Over the next several days she improved then 3 months later symptoms reoccurred. Pain at night, in AM, with stiffness and limited flexion noted. Seen by ortho and rheum 2 days apart and a sedated MRI-w/wo of lumbar spine, pelvis, femur and knee demonstrated a discoid lateral meniscus with horizontal tear and parameniscal cyst.

Discussion: A discoid meniscus is a congenital variant in which the meniscus is abnormally shaped, resembling a disc rather than a crescent. A discoid meniscus is a relatively uncommon abnormality that often goes unrecognized or untreated. It can have various types such as Wrisberg, incomplete and complete. Many discoid menisci are asymptomatic. However symptomatic ones can be treated conservatively or surgically. Conservative treatment included short-term knee immobilization and therapy. Surgical treatment includes partial removal of the torn portion and restoring the anatomical configuration. Complete meniscectomy should be avoided. The average age of diagnosis is > 10 years. Various studies show the average time frame for surgery ranges from 1 month to > 6 years.

Conclusion: The child was symptomatic for 4 weeks when Mom came to pediatric sports medicine clinic and after extensive discussion physical therapy was initiated. Symptoms resolved after 4 weeks of therapy. Surgery is scheduled within the month at the time of this submission. The youngest reported case in the literature of a discoid meniscus tear that had arthroscopy is age 6. This case represents an unusually early presentation in an extremely young child that had a very extensive workup to discover the cause of her symptoms and involved consultation with many musculoskeletal specialists. Shared decision making is crucial in deciding whether to perform an arthroscopy on such a developmentally immature meniscus versus encouraging prolonged conservative treatment to allow the child's knee to grow and develop more which might allow for a technically easier surgery. This case is important for pediatricians to be aware of and keep orthopedic congenital abnormalities on the differential diagnosis of a limp. It also illustrates that there can be value to performing a diagnostic MRI under sedation in the right setting.