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Knee injuries present frequently in virtually all age groups within a pediatric practice. The age and mechanism of injury are guidelines to a correct diagnosis. A swollen, painful knee in an infant should raise the suspicion of child abuse or infection. In the young child, significant ligament or meniscal injuries are rare, but epiphyseal separations and fractures are more frequent. In the adolescent, internal injuries to menisci and ligaments are frequent findings and most often result from sports activities, with or without contact. Patellar dislocations are also more common in adolescents.

The examiner should note bruising, swelling about the knee, the presence or absence of an effusion, and the ability to walk or bear weight. Most significant injuries are accompanied by an effusion or hemarthrosis, and the swollen knee is difficult to examine due to pain and limited motion. After the initial swelling has resolved, specific findings of an internal derangement can be elicited. The torn anterior cruciate is indicated by a positive Lachman test, in which the tibia can be translated anteriorly with the knee flexed 20°. Meniscal tears often produce pain when the knee is fully flexed and extended with medial or lateral rotational stress. Medial collateral and lateral collateral ligament injuries allow the joint to open either medially or laterally with stress in a 20° flexed position.

Radiographs should be evaluated and will show effusion in the case of internal derangement such as ligamentous injury or injury to the articular cartilage or meniscus. Widening of the distal femoral growth plate suggests a separation injury of the growth plate (Salter-Harris 1). Elevation of the tibial spine indicates an injury in which the anterior cruciate pulls a fragment of bone from the tibial articular surface. Other avulsion fractures about the knee are commonly detected on radiographs.

Initial treatment usually consists of splinting with compression using a prefabricated knee immobilizer and flexible elastic bandage (ie, ACEt brand). Aspiration of the knee is not necessary. Reevaluation at 2 weeks allows for a better physical exam for significant injury. Minor injuries will usually be recovering by then, and significant injuries will show persistent physical findings by that time. A magnetic resonance imaging (MRI) examination will help to define internal injuries that will require orthopedic consultation.


A discoid meniscus is an abnormally shaped lateral meniscus found in children of all ages (Fig. 211-1). The spectrum of abnormalities ranges from a minor excess of central tissue in an otherwise normal meniscus, to a grossly malformed unstable mass of meniscoid tissue with few tibial or capsular attachments. It may slip in and out of the joint, causing the patient to feel something pop over the lateral aspect of the knee joint. It may be somewhat painful. The examiner can feel something pop along the lateral joint line as the knee is flexed and ...

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