Understanding the Convex-Concave Rule

Purpose

• To understand arthrokinematics, which refers to the movement of joint surfaces.
• Helps in visualizing how different joints, such as the shoulder and elbow, move.

Definitions

Concave Surface

• Think of it as a surface that is "caved in."

Convex Surface

• Opposite of concave, more like a rounded surface.

The Convex-Concave Rule

• The rule is dependent on which joint surface is moving.

Concave Surface Moving

• Example: Elbow joint
  • Ulna is the concave surface
  • Humerus is the convex surface
  • When the concave surface moves, both the surface and the bone slide in the same direction.

Convex Surface Moving

• Example: Shoulder joint
  • Humerus is the convex surface
  • Scapula is the concave surface
  • When the convex surface moves, the bone moves in the opposite direction.

Conclusion

• The convex-concave rule is a fundamental concept in understanding joint movements in physical therapy.
• Questions related to physical therapy or the video can be asked through comments.

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