Depth-dependent Relaxation of Articular Cartilage in Unconfined Compression

INTRODUCTION Articular cartilage (AC) is an inhomogeneous, anisotropic and multiphasic composite. Depth-dependent strain distribution in full thickness AC has previously been investigated with optical methods (Guilak, 1995; Schinagl, 1997; Wang, 2003). Depth and time-dependent compressive strain has been predicted with theoretical models (Li, 2000; Wang, 2001). Most recently, Electronic Speckle Pattern Interferometry (ESPI) has been employed to measure depth-dependent strain on AC cross-sections in response to incrementally applied strain (Erne, 2003). In this study, we used ESPI to measure depth and time-dependent strain over the cross-section of AC. We hypothesized, that the strain in the superficial zone of AC will increase during relaxation, while strain in the deep zones will decrease.