A joint is a place where bones meet. An elbow-like hinge mainly bends and straightens in one plane. A shoulder-like ball-and-socket joint can move in more directions. The model keeps the bones joined while comparing permitted movement. First choose the kind of joint, then choose a direction to test.
The human body · Discover & try
Why do different joints allow different movements?
Reading level 1 of 5 · EarlyChange
Word help
Hinge joint
A joint allowing mainly bending and straightening.
Ball-and-socket
A joint allowing movement about several axes.
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See how it works
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Illustrative joint geometry and angles. Real joint movement also depends on surrounding ligaments, muscles and other tissues.
What to look for
- The connected bone can bend and straighten in its main plane.
- The ideal hinge stays still and the blocked-direction mark appears.
- This geometry permits the side-plane movement.
Explain what you noticed
A hip can move a thigh in several directions. Which model best explains that connection?
Keep this idea: Joint structure permits some movements and constrains others.
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Source material checked 2026-10-29. Explanations and activities by Nepedia. Source links do not imply endorsement.
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