Patellar Dislocations The patella can be acutely dislocated when a force displaces the patella laterally while the foot is planted It may remain dislocated or can reduce spontaneously The child will present with an acutely swollen knee with pain to palpation especially along the medial patella retinaculum If the patella is already reduced, displacement of the patella laterally will elicit an apprehension sign where the patient may state concern the kneecap feels like it is going to “pop out.” If the patella is still dislocated, this is clinically evident with an inability to completely extend the knee and an abnormal contour of the patella Radiograph examination can also identify patellar dislocation, but is not usually required To reduce the patella, the knee should be extended with a medial upward force on the lateral patella (see Chapter 130 Procedures , section on Closed Reduction of Dislocations) Radiographs of the knee should be obtained after reduction to evaluate for possible osteochondral fracture of the lateral femoral condyle or the medial patella facet, although these fractures are not always easily identified on x-ray After reduction, the knee should be immobilized in an above-the-knee posterior splint or knee immobilizer for weeks Outpatient orthopedic referral is recommended for follow-up Patellar Fractures Fractures of the patella are relatively uncommon in children compared to adults due to the thick cartilage covering the patella during a child’s growth and development In adolescents, fractures of the patella become more common They may present as osteochondritis dissecans from overuse, symptomatic bipartite conditions, avulsion or “sleeve” fractures, or transverse displaced fractures A congenital bipartite patella may be mistaken for a fracture on x-ray as an accessory ossification center is located along the superior lateral margin of the patella with smooth and rounded margins ( Fig 111.43 ) A sleeve fracture, which occurs when the lower half of the cartilage cap is avulsed by the patellar ligament, may also be difficult to diagnose on x-ray It may only be apparent by a small piece of bone visualized at the superior margin of the patellar ligament as the visible bony portion of the patella is displaced superiorly by the quadriceps ( Fig 111.44 ) This injury presents with pain preventing active extension of the knee A radiograph of the contralateral knee may assist in the diagnosis Urgent orthopedic consultation should be obtained Nondisplaced patellar fractures may be managed with a cast for to weeks Displaced fractures of more than 3- to 4mm displacement may require open reduction and internal fixation