Adhesion-Cohesion

Last Updated: Thursday, February 10, 2005

What is it?

Adhesion-cohesion is a stabilizing mechanism by which joint surfaces wet with joint fluid are held together by the molecular attraction of the fluid to itself and to the joint surfaces.

Cohesion and adhesion

Fluids such as water and joint fluid demonstrate the property of cohesion that is", they tend to hang together. Some surfaces, such as clean glass or articular cartilage, can be wet with water or synovial fluid, meaning that the fluid adheres to them. When two surfaces with adherent fluid are brought in contact, the adhesion of the fluid to the surfaces and the cohesion of the fluids tend to hold the two surfaces together. The amount of stability generated by adhesion-cohesion is related to the adhesive and cohesive properties of the joint fluid, the wetability of the joint surfaces, and the area of contact between the glenoid socket and the humerus.

Stabilizing effect

The magnitude of the stabilizing effect of adhesion-cohesion in the glenohumeral joint is unknown. The known wetability of articular cartilage and the cohesiveness of joint fluid suggest that this adhesion-cohesion mechanism could conserve energy by providing stability against low distracting loads without use of muscle action. This mechanism can function in any position of the glenohumeral joint.

Factors reducing effect

Stability from adhesion-cohesion is reduced by any factors that would lower either the cohesion of joint fluid (such as in inflammatory joint disease)", the degree to which the joint surfaces could be wet (such as in degenerative joint disease)," or the glenohumeral contact area (such as in a displaced articular surface fracture or a congenitally small glenoid).

Movie

Glenoid-labrum suction cup and adhesion-cohesion forces

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