Open Access Thesis
Date of Award
Purpose: To examine the relationship between well-shouldered osteochondral defects and
defects of different geometries by studying their effects on rim stress concentration and
load redistribution in the human knee.
Methods: Ten fresh-frozen cadaveric knees were mounted at 30Â° of flexion in a materials
testing machine. Digital electronic pressure sensors were placed in the medial and lateral
compartments of the knee. Dynamic pressure readings were recorded throughout the
loading and holding phases as each knee was loaded to 700N and held for 5 seconds.
Artificial defects were created in each knee to simulate well-shouldered defects and
beveled-defects. Loading was repeated for well-shouldered and beveled osteochondral
defects sized 6, 8, 10, 12, 14, 16, 18 and 20 mm.
Results: Stress concentrations around rims of defects were shown to act similarly to a
previous study by Guettler et al. As defect size increased, a rim of peak pressures formed
on the adjacent cartilage with distance from defect center to rim of peak pressures increasing as defect size increased (p<0.05). Average radius from the center to the rim of
peak pressure was found to be higher among beveled defects although this was not found
to be statistically significant. Peak pressure values did not increase significantly as
defects were enlarged.
Conclusions: Beveled defects were found to affect rim stress concentrations over their
well-shouldered counterparts. Although this result was not statistically significant,
multiple studies point to a link between osteochondral defects and degeneration of
surrounding articular cartilage. Based on this finding, it would be prudent when using a
size criterion in assessing severity of an osteochondral defect, to use the outermost border
of the defect as a measure of defect size.
Ensminger, Scott, "Contact pressure distribution of osteochondral defects of the knee: effects of non-vertical walls" (2012). Wayne State University Theses. 192.