Extraction of mechanical properties of articular cartilage from osmotic swelling behavior monitored using high frequency ultrasound

Q. Wang, Yongping Zheng, H. J. Niu, A. F.T. Mak

Research output: Journal article publicationJournal articleAcademic researchpeer-review

23 Citations (Scopus)


Articular cartilage is a biological weight-bearing tissue covering the bony ends of articulating joints. Negatively charged proteoglycan (PG) in articular cartilage is one of the main factors that govern its compressive mechanical behavior and swelling phenomenon. PG is nonuniformly distributed throughout the depth direction, and its amount or distribution may change in the degenerated articular cartilage such as osteoarthritis. In this paper, we used a 50 MHz ultrasound system to study the depth-dependent strain of articular cartilage under the osmotic loading induced by the decrease of the bathing saline concentration. The swelling-induced strains under the osmotic loading were used to determine the layered material properties of articular cartilage based on a triphasic model of the free-swelling. Fourteen cylindrical cartilage-bone samples prepared from fresh normal bovine patellae were tested in situ in this study. A layered triphasic model was proposed to describe the depth distribution of the swelling strain for the cartilage and to determine its aggregate modulus Haat two different layers, within which Hawas assumed to be linearly dependent on the depth. The results showed that Hawas 3.0 ± 3.2, 7.0 ± 7.4, 24.5 ± 11.1 MPa at the cartilage surface, layer interface, and deep region, respectively. They are significantly different (p < 0.01). The layer interface located at 70% ± 20% of the overall thickness from the uncalcified-calcified cartilage interface. Parametric analysis demonstrated that the depth-dependent distribution of the water fraction had a significant effect on the modeling results but not the fixed charge density. This study showed that high-frequency ultrasound measurement together with triphasic modeling is practical for quantifying the layered mechanical properties of articular cartilage nondestructively and has the potential for providing useful information for the detection of the early signs of osteoarthritis.
Original languageEnglish
Pages (from-to)413-422
Number of pages10
JournalJournal of Biomechanical Engineering
Issue number3
Publication statusPublished - 1 Jun 2007


  • Articular cartilage
  • Biomechanics
  • Elastography
  • Fixed charge density
  • Osmotic loading
  • Osteoarthritis
  • Proteoglycan
  • Triphasic theory
  • Ultrasound

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physiology (medical)


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