title: Displacing lateral meniscus masquerading as patella dislocation.
abstract: OBJECTIVE
  To alert the treating clinician to an uncommon knee meniscal condition that often masquerades as a more common patella condition.
  
  
  METHODS
  Retrospective chart review of a series of cases was undertaken. A series of 12 knees in 11 patients were referred to an orthopaedic surgeon with a diagnosis of recurrent lateral patella dislocation. Three knees had undergone patella realignment surgery with continuance of symptoms. Eight patients had prior magnetic resonance images read as no meniscal pathology and no acute patella/patella retinacular injury. All patients presented for a consult with a similar history.
  
  
  RESULTS
  Under anaesthesia, all knees had a stable patella as judged by physical examination. At the time of surgery, six patients had a frank tear in the lateral meniscus, all of which were readily displaceable. Six knees showed a displaceable lateral meniscus with attenuation but not a visible frank tear. Ten menisci were treated with repair, and two knees underwent partial lateral meniscectomies. Patient follow-up of minimally 18 months revealed no further episodes of "knee-cap dislocation" or symptoms of catching and locking.
  
  
  CONCLUSIONS
  The clinician treating a patient with a history of a knee locking in flexion should have a high index of suspicion for a lateral meniscus tear or an unstable hypermobile lateral meniscus, despite patient report of perceived patella movement. History of symptoms occurring in knee flexion and attention to patella physical examination should be key factors in this diagnostic conundrum.
  
  
  METHODS
  Retrospective chart review, Level IV.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue South, Suite R200, Minneapolis, MN, 55454, USA, arend001@umn.edu.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Arendt
authors.forename: Cristián A
authors.initials: CA
authors.lastname: Fontboté
authors.forename: Sara R
authors.initials: SR
authors.lastname: Rohr
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery; D004204:Joint Dislocations / Q000601:surgery; D007718:Knee Injuries / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008592:Menisci, Tibial / Q000601:surgery; D008875:Middle Aged; D010329:Patella; D031222:Patellar Dislocation / Q000175:diagnosis*; D010808:Physical Examination; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012421:Rupture / Q000473:pathology; D000070600:Tibial Meniscus Injuries; D055815:Young Adult