title: The effects of articular, retinacular, or muscular deficiencies on patellofemoral joint stability: a biomechanical study in vitro.
abstract: Normal function of the patellofemoral joint is maintained by a complex interaction between soft tissues and articular surfaces. No quantitative data have been found on the relative contributions of these structures to patellar stability. Eight knees were studied using a materials testing machine to displace the patella 10 mm laterally and medially and measure the force required. Patellar stability was tested from 0 degrees to 90 degrees knee flexion with the quadriceps tensed to 175 N. Four conditions were examined: intact, vastus medialis obliquus relaxed, flat lateral condyle, and ruptured medial retinaculae. Abnormal trochlear geometry reduced the lateral stability by 70% at 30 degrees flexion, while relaxation of vastus medialis obliquus caused a 30% reduction. Ruptured medial retinaculae had the largest effect at 0 degrees flexion with 49% reduction. There was no effect on medial stability. There is a complex interaction between these structures, with their contributions to loss of lateral patellar stability varying with knee flexion.
authors.affiliation: Biomechanics Section, Mechanical Engineering Department, Room 638 Mechanical Engineering Building, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
authors.forename: W
authors.initials: W
authors.lastname: Senavongse
authors.forename: A A
authors.initials: AA
authors.lastname: Amis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology; D010329:Patella / Q000503:physiopathology*; D031222:Patellar Dislocation / Q000503:physiopathology; D016059:Range of Motion, Articular