Saddle and condyloid joints involve the concave surface of one bone sliding over the convex surface of another bone and allow motion in how many planes?

• A. Two planes
• B. One plane
• C. Three planes
• D. Infinite planes

Answer: (A)

These joints are biaxial in their movement. When the concave surface of one bone slides against the convex surface of the other, they permit motion in two perpendicular planes: flexion–extension in one plane and abduction–adduction in the other. Circumduction can occur as a combination of those two movements, but rotation about the bone’s long axis is limited. So saddle and condyloid joints move in two planes, not in just one, nor in three or unlimited planes.