title: Development of the human knee joint.
abstract: Many studies have been published on the development of the human knee joint, but different investigators disagree on its morphogenetic time table. Most discrepancies center on the cavitation of the knee joint and the participation of the superior tibiofibular joint in the joint knee system.
  
  
  
  We summarize our observations of the development of the knee joint in 50 serially sectioned human embryonic and fetal lower limbs (26 embryos and 24 fetuses).
  
  
  
  The epiphysis of the femur and tibia become condryfied from O'Rahilly stage 18, and ossification begins during the 13th week of development. The patella appears as a dense blastema during O'Rahilly stage 19, becomes condryfied during O'Rahilly stage 22, and begins its ossification during the 14th week of development. The knee joint cavity appears during O'Rahilly stage 22, initially as the femoropatellar joint. This process begins at the periphery of the articular interzone. The superior tibiofibular joint communicates with the lateral meniscotibial joint between 10 and 11 weeks of development and becomes separated from the 13 week on. The menisci arise from the eccentric portions of the articular interzone during O'Rahilly stage 22; however, until week 9 of development, they are not easily distinguishable.
  
  
  
  We establish the morphogenetic time table of the human knee joint.
authors.affiliation: Department of Morphological Sciences, University of Granada, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Mérida-Velasco
authors.forename: I
authors.initials: I
authors.lastname: Sánchez-Montesinos
authors.forename: J
authors.initials: J
authors.lastname: Espín-Ferra
authors.forename: J F
authors.initials: JF
authors.lastname: Rodríguez-Vázquez
authors.forename: J R
authors.initials: JR
authors.lastname: Mérida-Velasco
authors.forename: J
authors.initials: J
authors.lastname: Jiménez-Collado
mesh_terms: D002356:Cartilage / Q000196:embryology; D004838:Epiphyses / Q000196:embryology; D005269:Femur / Q000196:embryology*; D006801:Humans; D007719:Knee Joint / Q000196:embryology*; D008592:Menisci, Tibial / Q000196:embryology; D010012:Osteogenesis; D013977:Tibia / Q000196:embryology*; D013997:Time Factors