Mobilization/Convex-Concave Rule. NPTE Study Guide: Master the NPTE

What’s osteokinematics?

Movement between bones. ("osteo" refers to bones & "kinematics" refers to the study of motion).

What’s arthrokinematics?

Movement between joint surfaces. ("arthro" refers to joints).

What’s joint Arthrokinematics?

Describes movements within joints, including roll, glide/slide, and spin.

What’s roll?

Movement where one joint surface rolls on another in a specific direction, akin to a tire rolling on a road.

What’s glide/slide?

Pure translatory motion of one surface gliding on another within the joint, similar to braked wheels skidding.

What’s spin?

Rotation of a movable component of a joint. (Note: Not commonly on the NPTE)

What’s the Concave–Convex Rule?

Explains the relationship between osteokinematics and arthrokinematics based on the shapes of the surfaces involved.

What does concave mean?

Hollowed or rounded inward

What does convex mean?

Curved or rounded outward

What’s concave on convex?

Glide occurs in the same direction. If a moving surface is concave, the slide occurs in the same direction as the roll.

Mnemonic—concAve=sAme.

Example: elbow flexion—Roll & slide are both occurring anteriorly; Ulna (concave) is moving on the humerus (convex)

What’s convex on concave?

Glide occurs in the opp direction. If a moving surface is convex, the slide occurs in the opp direction of the roll.

Mnemonic: cOnvex = Opposite.

Example: shoulder abduction—Roll is occurring superiorly, whereas slide is occurring inferiorly; Humerus (convex) is moving on the glenoid fossa (concave)

What are thumb mechanics?

Describes movements in the thumb saddle joint, including radial adduction/abduction and palmar adduction/abduction.

Thumb concave on convex is made up of which movements?

Radial adduction (flexion) and radial abduction (extension).

How does thumb concave on convex work?

Distal concave moves on proximal convex (same direction).

Radial adduction (flexion) = ulnar glide.

Radial abduction (extension) = radial glide

Thumb convex on concave is made up of which movements?

Palmar adduction and palmar abduction

How does thumb convex on concave work?

Distal convex moves on proximal concave (opposite direction).

Palmar adduction = volar (anterior) glide.

Palmar abduction = dorsal (posterior) glide

Thumb flexion example

When going into thumb flexion it’s pointing to the ulnar side of your arm, telling you that it’s an ulnar roll.

Thumb extension example

When going into thumb extension it’s pointing to the radial side of your arm, telling you that it’s a radial roll.

Thumb abduction example

When going into thumb abduction it’s creating a “V” (between the 1st & 2nd digits), telling you that it’s rolling volar

Thumb adduction example

When going into thumb adduction it’s coming into your hanD, telling you that it’s rolling Dorsal