Surface fissures in articular cartilage: new concepts, hypotheses and modeling.

Objective: Clarification and mesomechanical modeling of the inception of fissures at the surface of articular cartilage.

Design: Articular cartilage is described as a macroscopically heterogeneous medium consisting of zones - layers - with different orientation of collagen fibers.

Background: Degradation of mechanical properties of cartilage is a serious, still not fully clarified problem that deserves attention.

Methods: Theoretical analysis based on a survey of known experimental findings related to the subject. The general author's mesomechanical concept of modeling heterogeneous media is applied to the elucidation and description of the formation of fissures at the surface of articular cartilage.

Results: Our model clarifies how the high tensile stresses in the collagen fibers of the superficial tangential zone depend on the rate of loading.

Conclusions: The superficial cracks are caused predominantly by a very quick loading. This explains among others the high incidence of post-traumatic osteoarthritis of the lower extremity after accidents and injuries in sports.

Relevance: Superficial fissures in articular cartilage are observed in joints with primary osteoarthritis. The current study specifies the kinds of loading that lead to their inception.