title: Isokinetic knee extensor strength deficit following matrix-induced autologous chondrocyte implantation.
abstract: BACKGROUND
  Autologous chondrocyte implantation has become an established technique for addressing knee cartilage defects. Despite reported improvement in pain and regeneration of hyaline-like repair tissue, little has been reported on the recovery of knee strength.
  
  
  METHODS
  Knee strength assessment was undertaken in 60 patients at 5 years following autologous chondrocyte implantation. Using an isokinetic dynamometer, and during isokinetic knee extension and flexion angular velocities of 60°, 90° and 120°/s, the peak torque, torque at 45° of knee flexion and hamstrings/quadriceps ratio was obtained, in both the operated and non-operated limbs. Pain at the time of assessment was obtained. Independent sample t-tests were used to assess differences in the operated and non-operated sides.
  
  
  RESULTS
  There were no significant differences (p>0.05) between the operated and non-operated legs in the peak knee flexor torque or knee flexor torque at a knee flexion angle of 45°, at all angular velocities (60°, 90° and 120°/s). While the peak knee extensor torque was less in the operated leg at all angular velocities, these differences were not significant (p>0.05). However, a significantly reduced (p<0.05) knee extensor torque at a knee flexion angle of 45°, was observed at all speeds.
  
  
  CONCLUSIONS
  While patients had recovered their knee flexor strength, they still demonstrated a reduced knee extensor strength profile at 5 years. This demonstrates that the early supervised rehabilitation phase following autologous chondrocyte implantation is not sufficient to restore long-term knee strength, and ongoing patient advice and rehabilitation is required extending beyond this early period. It is unknown how this prolonged reduction in strength may affect long-term graft outcome.
authors.affiliation: School of Sport Science, Exercise and Health, University of Western Australia, Crawley, Perth, WA 6009, Australia. jay.ebert@uwa.edu.au
authors.forename: Jay R
authors.initials: JR
authors.lastname: Ebert
authors.forename: David G
authors.initials: DG
authors.lastname: Lloyd
authors.forename: David J
authors.initials: DJ
authors.lastname: Wood
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Ackland
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000166:cytology; D002357:Cartilage Diseases / Q000601:surgery*; D017690:Cell Transplantation; D019902:Chondrocytes / Q000166:cytology*; D005260:Female; D006801:Humans; D007700:Kinetics; D007717:Knee / Q000502:physiology; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D010146:Pain; D012038:Regeneration; D019415:Torque; D014182:Transplantation, Autologous