Proko Lesson: Types of Joints in the Human Body

Introduction to Joints

• Purpose of Joints: Define motion and limitations of the body.
• Focus for Artists: Synovial joints are crucial due to their movement (e.g., shoulder, knee).
• Less Relevant for Artists: Fibrous and cartilaginous joints, like the pubic bones, are less important as they barely or don't move.

Importance of Synovial Joints

• Functionality: Key to creating realistic squash and stretch in drawings.
• Position Awareness: Knowing joint positions aids in realistic depictions of movement.

Types of Synovial Joints

1. Hinge Joint

   • Allows movement on one axis (flexion and extension).
   • Example: Elbow, like a door hinge, only allows opening or closing.

2. Pivot Joint

   • Allows rotation at one axis, along the long axis.
   • Example: Radial ulnar joint, responsible for pronation and supination of the forearm.

3. Ball and Socket Joint

   • Allows movement in all axes (flexion, extension, abduction, adduction, rotation, circumduction).
   • Examples: Hip and shoulder; shoulder has a greater range of motion but less stability.

4. Ellipsoid Joint

   • Similar to ball and socket but prevents rotation.
   • Allows movement on two axes (flexion, extension, abduction, adduction, circumduction).
   • Example: Wrist (radial carpal joint).

5. Saddle Joint

   • Allows flexion, extension, abduction, adduction, circumduction, and slight rotation.
   • Example: Carpometacarpal joint of the thumb.

6. Plane Joint

   • Two flat-ish surfaces allowing gliding or rotation.
   • Examples: Carpal and tarsal bones, acromioclavicular joint.

Cartilaginous Joints

• Exception for Artists: The spine is crucial and will be covered in the next lesson.

Assignments

• Activity 1: Identify and study the movement of joints on yourself using images.
• Activity 2: Draw simple versions of the joints and post them for critique.

Additional Resources

• PDF e-book: Defines anatomical terms and joint types with visual aids.
• 3D Model of RoboSkelly: Simplified skeleton for study and drawing.
• Premium Features: Available at proko.com/anatomy.

Conclusion

• Community and Learning: Share work in the Facebook group for critique and learning from Marshall Vandruff.
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