General Joint Biomechanics

Question 1

What are three ways to classify joints?

Answer 1

i) complexity: simple, compound, complex
ii) shape: (un)modified ovoid, (un)modified sellar
iii) type: ball and socket, hinge, planar etc.

Question 2

What are the six joint types?

Answer 2

i) pivot
ii) hinge
iii) ellipsoid
iv) saddle
v) planar
vi) ball & socket

Question 3

What is meant by modified ovoid?

Answer 3

2 DOF. Egg-shaped.

Question 4

What is meant by unmodified ovoid?

Answer 4

3 DOF. Spherical.

Question 5

What is meant by sellar?

Answer 5

2 DOF. Purely concave and convex, joint surfaces are perpendicular to each other. Ex. 1st CMC

Question 6

What is meant by modified sellar?

Answer 6

1 DOF. Concave and convex in the same plane, joint surfaces are not perpendicular. ex. calcaneocuboid

Question 7

What is a DOF?

Answer 7

The number of independent stationary axes that a joint can rotate around at perpendicular angles to each other.

Question 8

How many spins can one joint possess arthrokinematically?

Answer 8

Only one. If a joint has 3 DOF, it must be a spin and two swings.