title: Phenomenon of painless knee in recurrent patellar dislocation in children.
abstract: BACKGROUND
  Cartilage lesion with patellar malalignment may be correlated with pain. Situations in which patients with recurrent patellar dislocation are painless between episodes of luxation can be approached with considerable curiosity. We evaluated the distribution of substance-P and S-100 protein expression in soft tissue of the knee in children with recurrent patellar dislocation, in order to evaluate the distribution of nociceptors and determine tissue origins of this situation.
  
  
  METHODS
  Samples were collected from the medial and lateral synovial membrane, medial and lateral patellar retinaculum, Hoffa's body, patellar ligament, and quadriceps' aponeurosis in 10 children during the Blauth procedure and 10 adults with idiopathic osteoarthritis during total joint alloplasty. The density of nociceptive fibres was compared in the children and adults using S-100 and substance-P monoclonal antibodies.
  
  
  RESULTS
  Statistical differences between groups were demonstrated for S-100 expression in synovial membrane of the medial knee compartment (p < 0.05) and for substance-P expression in the medial patellar retinaculum (p < 0.05) and synovial membrane of the lateral (p < 0.05) and medial (p < 0.05) knee compartment in favour of children.
  
  
  CONCLUSIONS
  Lack of pain sensations in patients with recurrent patellar dislocation may be associated with non-increased expression of nerve endings in Hoffa's body. Increased expression of either S-100 protein or substance-P in synovial membrane and the medial retinaculum did not induce pain development in the knee joints of that group of patients.
authors.affiliation: Clinic of Orthopaedics and Paediatric Orthopaedics, Medical University of Lodz, Poland.
authors.forename: Adrian
authors.initials: A
authors.lastname: Masłoń
authors.affiliation: Department of Reconstructive Surgery and Arthroscopy of the Knee, Medical University of Lodz, Poland.
authors.forename: Dariusz
authors.initials: D
authors.lastname: Witoński
authors.affiliation: Pathomorphology and Clinical Cytopathology Department, Medical University of Lodz, Poland.
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Modrzewski
authors.affiliation: Orthopaedic Department, Kopernik Memorial Regional Specialized Hospital, Lodz, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Grabicki
authors.affiliation: Clinic of Orthopaedics and Paediatric Orthopaedics, Medical University of Lodz, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Sibiński
authors.affiliation: Clinic of Orthopaedics and Paediatric Orthopaedics, Medical University of Lodz, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Grzegorzewski
keywords: S-100 protein; children; painless knee joint; recurrence patellar dislocation; substance-P
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