Unconfined creep compression of chondrocytes

Nic D. Leipzig, Kyriacos A. Athanasiou

Research output: Contribution to journalArticlepeer-review

97 Scopus citations


The study of single cell mechanics offers a valuable tool for understanding cellular milieus. Specific knowledge of chondrocyte biomechanics could lead to elucidation of disease etiologies and the biomechanical factors most critical to stimulating regenerative processes in articular cartilage. Recent studies in our laboratory have suggested that it may be acceptable to approximate the shape of a single chondrocyte as a disc. This geometry is easily utilized for generating models of unconfined compression. In this study, three continuum mechanics models of increasing complexity were formulated and used to fit unconfined compression creep data. Creep curves were obtained from middle/deep zone chondrocytes (n=15) and separately fit using the three continuum models. The linear elastic solid model yielded a Young's modulus of 2.55±0.85kPa. The viscoelastic model (adapted from the Kelvin model) generated an instantaneous modulus of 2.47±0.85kPa, a relaxed modulus of 1.48±0.35kPa, and an apparent viscosity of 1.92±1.80kPa-s. Finally, a linear biphasic model produced an aggregate modulus of 2.58±0.87kPa, a permeability of 2.57×10-12±3. 09m4/N-s, and a Poisson's ratio of 0.069±0.021. The results of this study demonstrate that similar values for the cell modulus can be obtained from three models of increasing complexity. The elastic model provides an easy method for determining the cell modulus, however, the viscoelastic and biphasic models generate additional material properties that are important for characterizing the transient response of compressed chondrocytes.

Original languageEnglish (US)
Pages (from-to)77-85
Number of pages9
JournalJournal of Biomechanics
Issue number1
StatePublished - Jan 2005
Externally publishedYes


  • Articular cartilage
  • Biphasic theory
  • Cellular engineering
  • Chondrocyte
  • Mechanotransduction
  • Modeling
  • Single cell mechanics
  • Unconfined compression
  • Viscoelasticity

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine


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