Figure 6.

The effective compressive modulus, ${\mu }_{eff}$, in three zones of cartilage. (a) The effective compressive modulus, ${\mu }_{eff}$, in three zones in a simulated ‘mature and healthy’ cartilage, using the stress-strain relationship (slope of linear fit represents the ${\mu }_{eff}$). For the SZ the modulus is ~1 MPa and it increases to ~1.6 MPa in the deep region (RZ). (b) The effective compressive modulus, ${\mu }_{eff}$, in three zones in a simulated ‘degraded’ cartilage that has a reduced PG content. Loss of PG or FCD results in an increase in the intra-tissue strains (~50%) for the given stress, and consequently a decrease in effective modulus (slope of linear fit) for each zone.