A patellar sleeve fracture is an avulsion of the inferior pole of the patella. The mechanism of injury is a forceful eccentric contraction of the quadriceps. Instead of rupturing the patellar tendon, as would be seen in adults, this contraction avulses a fragment of distal patellar bone and cartilage (i.e., the “patellar sleeve”).
Patients present with anterior knee pain, hemarthrosis, and inability to perform a straight leg raise (i.e., the extensor mechanism is not intact). In some cases, with wide displacement of the fragments, a defect can also be felt over the distal patella at the location of the injury.
Full Article - https://www.orthopaedia.com/pediatric-fractures-of-the-lower-extremities/#Patellar-Sleeve
