title: In vivo measurement of localized tibiofemoral cartilage strains in response to dynamic activity.
abstract: BACKGROUND
  Altered local mechanical loading may disrupt normal cartilage homeostasis and play a role in the progression of osteoarthritis. Currently, there are limited data quantifying local cartilage strains in response to dynamic activity in normal or injured knees.
  
  
  OBJECTIVE
  To directly measure local tibiofemoral cartilage strains in response to a dynamic hopping activity in normal healthy knees. We hypothesized that local regions of cartilage will exhibit significant compressive strains in response to hopping, while overall compartmental averages may not.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Both knees of 8 healthy subjects underwent magnetic resonance imaging before and immediately after a dynamic hopping activity. Images were segmented and then used to create 3-dimensional surface models of bone and cartilage. These pre- and postactivity models were then registered using an iterative closest point technique to enable site-specific measurements of cartilage strain (defined as the normalized change in cartilage thickness before and after activity) on the femur and tibia.
  
  
  RESULTS
  Significant strains were observed in both the medial and lateral tibial cartilage, with each compartment averaging a decrease of 5%. However, these strains varied with location within each compartment, reaching a maximum compressive strain of 8% on the medial plateau and 7% on the lateral plateau. No significant averaged compartmental strains were observed in the medial or lateral femoral cartilage. However, local regions of the medial and lateral femoral cartilage experienced significant compressive strains, reaching maximums of 6% and 3%, respectively.
  
  
  CONCLUSIONS
  Local regions of both the femur and tibia experienced significant cartilage strains as a result of dynamic activity. An understanding of changes in cartilage strain distributions may help to elucidate the biomechanical factors contributing to cartilage degeneration after joint injury.
  
  
  CONCLUSIONS
  Site-specific measurements of in vivo cartilage strains are important because altered loading is believed to be a factor contributing to the development and progression of osteoarthritis. Specifically, this methodology and data could be used to evaluate the effects of soft tissue injuries (such as ligament or meniscus tears) on cartilage strains in response to dynamic activities of daily living.
authors.affiliation: Duke Sports Medicine Center, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: E Grant
authors.initials: EG
authors.lastname: Sutter
authors.affiliation: Duke Sports Medicine Center, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA.
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Widmyer
authors.affiliation: Duke Sports Medicine Center, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: Gangadhar M
authors.initials: GM
authors.lastname: Utturkar
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Spritzer
authors.affiliation: Duke Sports Medicine Center, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Garrett
authors.affiliation: Duke Sports Medicine Center, Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA lou.defrate@duke.edu.
authors.forename: Louis E
authors.initials: LE
authors.lastname: DeFrate
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000502:physiology*; D005080:Exercise Test; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D013977:Tibia / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: biomechanics; cartilage; hopping; jumping; knee; magnetic resonance imaging; osteoarthritis; strain; stress test; tibiofemoral