title: A rare patella anatomical abnormality causing locking in an adolescent girl.
abstract: Locking is an inability to fully extend the knee and is most commonly associated with meniscal pathology and loose bodies. The locked knee is an infrequent presentation in paediatric orthopaedics, and the presence of a patella protuberance as a cause has never been reported in children or adults. An adolescent female presented with a 4-year history of intermittent locking of the right knee associated with a painful audible 'clunk' on full extension. Plain film radiographs and computed tomography showed a posteriorly projecting bony protuberance over the inferior aspect of the patella. The protuberance was removed via an arthrotomy, and the patient made significant improvement in pain and function with no further locking episodes experienced.
  
  
  METHODS
  IV.
authors: Royal National Orthopaedic Hospital, Stanmore, Middlesex, HA7 4LP, UK. ivanhegan@nhs.net
authors: Ivor
authors: I
authors: Vanhegan
authors: Bhupinder
authors: B
authors: Mann
authors: Daniel Alexander
authors: DA
authors: Schaerf
authors: John Andrew
authors: JA
authors: Skinner
mesh_terms: D000293:Adolescent; D001182:Arthroscopy; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010329:Patella / Q000002:abnormalities* / Q000000981:diagnostic imaging; D011859:Radiography; D016059:Range of Motion, Articular