Related Experiment Video
Updated: Apr 29, 2026
An Experimental and Finite Element Protocol to Investigate the Transport of Neutral and Charged Solutes across Articular Cartilage
Published on: April 23, 2017
Molecular origin of a loading-induced black layer in the deep region of articular cartilage at the magic angle
Nian Wang1, David Kahn, Farid Badar
1Department of Physics and Center for Biomedical Research, Oakland University, Rochester, Michigan, USA.
Purpose:
To investigate the molecular origin of an unusual low-intensity layer in the deep region of articular cartilage as seen in magnetic resonance imaging (MRI) when the tissue is imaged under compression and oriented at the magic angle.
Materials And Methods:
Microscopic MRI (μMRI) T2 and T1 ρ experiments were carried out on 18 specimens, both native and degraded (treated with trypsin). The glycosaminoglycan (GAG) concentrations in the specimens were quantified by both sodium ICP-OES and μMRI Gd(DTPA)(2-) -contrast methods. The mechanical modulus of the specimens was also measured.
Results:
Native tissue shows no load-induced layer, while the trypsin-degraded tissue shows clearly the low-intensity line at the deep part of tissue. The GAG reductions were confirmed by the sodium ICP-OES (from 81.7 ± 5.4 mg/mL to 9.2 ± 3.4 mg/mL), MRI GAG quantification (from 72.4 ± 6.7 mg/mL to 11.2 ± 2.9 mg/mL). The modulus reduction was confirmed by biomechanics (from 4.3 ± 0.7 MPa to 0.3 ± 0.1 MPa).
Conclusion:
Both T2 and T1 ρ profiles in native and degraded cartilage show strongly strain-, depth-, and angle-dependence using high-resolution MRI. The GAG reduction is responsible for the visualization of a low-intensity layer in deep cartilage when it is loaded and oriented at 55°.
