Arthrokinematics

Arthrokinematics refers to the movement of joint surfaces.

The angular movement of bones in the human body occurs as a result of a combination of rolls, spins, and slides.

A roll is a rotary movement, one bone rolling on another.

A spin is a rotary movement, one body spinning on another.

A slide is a translatory movement, sliding of one joint surface over another.

The convex-concave rule is the basis for determining the direction of the mobilizing force when joint mobilization gliding techniques are used to increase a certain joint motion.

The direction in which sliding occurs depends on whether the moving surface is concave or convex. 

Concave = hollowed or rounded inward

Convex = curved or rounded outward

If the moving joint surface is CONVEX, sliding is in the OPPOSITE direction of the angular movement of the bone.

If the moving joint surface is CONCAVE, sliding is in the SAME direction as the angular movement of the bone.

 Examples:

Glenohumeral articulation: concave glenoid fossa articulates with the convex humeral head

Glenhumeral posterior glide increases flexion and internal rotation

Glenhumeral anterior glide increased extension and external rotation

'Humeroradial 'articulation: convex capitulum articulates with the concave radial head

Dorsal glide of the head of radius increases elbow extension

Volar glide of the head of the radius increases elbow flexion