ABSTRACT
The overall structure of articular cartilage is analogous to a jelly-led balloon. The proteoglycan (PG)-rich middle zone is osmotically pressurized, with Fluid restrained from exiting the tissue by the dense collagen network of the superficial zone and the calcified structure of the deep bone. The passive tensile tissues, tendon and ligament, are also composed largely of water and collagen, but contain very little of the PGs that give cartilage its unique mechanical properties. Performance characteristics of a muscle depend on both its intrinsic properties and the extrinsic organization of that tissue. The composition and structure of the tensile so tissues is quite similar to that of cartilage, and the biphasic theory can be applied to them as well. Fluid pressure serves a smaller role in tissues loaded in tension, and the complication of the biphasic model is generally unnecessary. For modeling of segmental mechanics, it is frequently sufficient to treat these structures according to a one-dimensional approximation.
