title: The progression of isokinetic knee strength after matrix-induced autologous chondrocyte implantation: implications for rehabilitation and return to activity.
abstract: BACKGROUND
  Matrix-induced autologous chondrocyte implantation (MACI) is an established technique for the repair of knee chondral defects. Despite the reported clinical improvement in knee pain and symptoms, little is known on the recovery of knee strength and its return to an appropriate level compared with the unaffected limb.
  
  
  OBJECTIVE
  To investigate the progression of isokinetic knee strength and limb symmetry after MACI.
  
  
  METHODS
  Prospective cohort.
  
  
  METHODS
  Private functional rehabilitation facility.
  
  
  METHODS
  58 patients treated with MACI for full-thickness cartilage defects to the femoral condyles.
  
  
  METHODS
  MACI and a standardized rehabilitation protocol.
  
  
  METHODS
  Preoperatively and at 1, 2, and 5 y postsurgery, patients underwent a 3-repetition-maximum straight-leg raise test, as well as assessment of isokinetic knee-flexor and -extensor torque and hamstring:quadriceps (H:Q) ratios. Correlation analysis investigated the association between strength and pain, demographics, defect, and surgery characteristics. Linear-regression analysis estimated differences in strength measures between the operated and nonoperated limbs, as well as Limb Symmetry Indexes (LSI) over time.
  
  
  RESULTS
  Peak knee-extension torque improved significantly over time for both limbs but was significantly lower on the operated limb preoperatively and at 1, 2, and 5 y. Mean LSIs of 77.0%, 83.0%, and 86.5% were observed at 1, 2, and 5 y, respectively, while 53.4-72.4% of patients demonstrated an LSI < or = 90% across the postoperative timeline. Peak knee-flexion torque was significantly lower on the operated limb preoperatively and at 1 year. H:Q ratios were significantly higher on the operated limb at all time points.
  
  
  CONCLUSIONS
  While peak knee-flexion and hip-flexor strength were within normal limits, the majority of patients in this study still demonstrated an LSI for peak knee-extensor strength < or = 90%, even at 5 y. It is unknown how this prolonged knee-extensor deficit may affect long-term graft outcome and risk of reinjury after return to activity.
authors.affiliation: School of Sport Science, Exercise and Health, University of Western Australia, Crawley, Perth, WA, Australia.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Ebert
authors.forename: Anne
authors.initials: A
authors.lastname: Smith
authors.forename: Peter K
authors.initials: PK
authors.lastname: Edwards
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Ackland
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D019902:Chondrocytes / Q000637:transplantation*; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000534:rehabilitation* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D011446:Prospective Studies; D020127:Recovery of Function / Q000502:physiology*; D014182:Transplantation, Autologous / Q000379:methods / Q000534:rehabilitation; D055815:Young Adult