title: Mechanical properties of the patellar tendon in elite volleyball players with and without patellar tendinopathy.
abstract: BACKGROUND
  Although differences in mechanical properties between symptomatic and healthy tendons have been observed for the Achilles tendon, the impact of tendinopathy on patellar tendon mechanics is not fully documented. The aim of the present case-control study was to assess the mechanical properties of the tendon and jump performance in elite athletes with and without patellar tendinopathy.
  
  
  METHODS
  We identified 17 male volleyball players with patellar tendinopathy and 18 healthy matched controls from a 5-year prospective cohort study on junior elite volleyball players. Outcome variables included three measures of maximal vertical jump performance and ultrasound-based assessments of patellar tendon cross-sectional area, stiffness and Young's modulus.
  
  
  RESULTS
  The proximal cross-sectional area of the patellar tendon was significantly larger in the tendinopathic group (133 ± 11 vs 112 ± 9 mm(2), respectively; p < 0.001). Pathological tendons presented lower stiffness (2254 ± 280 vs 2826 ± 603 N/mm, respectively; p = 0.006) and Young's modulus (0.99 ± 0.16 vs 1.17 ± 0.25 GPa, respectively; p = 0.04) than healthy tendons. However, the difference between the countermovement jump height and the squat jump height (3.4 ± 2.2 vs 1.2 ± 1.5 cm, p = 0.005) was significantly higher in the tendinopathic group compared with the control group.
  
  
  CONCLUSIONS
  Patellar tendinopathy is associated with a decrease in the mechanical and material properties of the tendon in elite athletes subjected to a high volume of jumping activity. However, compared with their healthy counterparts, tendinopathic volleyball players have a better ability to utilise the stretch-shortening cycle when jumping.
authors.affiliation: Department of Sports Medicine, Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Norway. christian.k.helland@gmail.com
authors.forename: Christian
authors.initials: C
authors.lastname: Helland
authors.forename: Jens
authors.initials: J
authors.lastname: Bojsen-Møller
authors.forename: Truls
authors.initials: T
authors.lastname: Raastad
authors.forename: Olivier R
authors.initials: OR
authors.lastname: Seynnes
authors.forename: Marie M
authors.initials: MM
authors.lastname: Moltubakk
authors.forename: Vidar
authors.initials: V
authors.lastname: Jakobsen
authors.forename: Håvard
authors.initials: H
authors.lastname: Visnes
authors.forename: Roald
authors.initials: R
authors.lastname: Bahr
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D016022:Case-Control Studies; D004548:Elasticity / Q000502:physiology; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D017847:Patellar Ligament / Q000033:anatomy & histology / Q000502:physiology*; D011446:Prospective Studies; D052256:Tendinopathy / Q000473:pathology / Q000503:physiopathology*; D054798:Volleyball / Q000293:injuries*; D055815:Young Adult
keywords: Biomechanics; Knee; Sporting injuries; Tendons; Ultrasound