Convex-Concave Rule: Describes the relationship between the surfaces and movements of bones in a joint
Convex Surface: The rounded part (e.g., fist with right hand)
Concave Surface: The hollowed part (e.g., left hand covering right hand)
Movements Demonstrations
Convex Moving on Concave:
When a convex bone moves, its surface moves in the opposite direction to the intended bone movement
Example: Raising the arm (clavicle and sternum joint)
Clavicle head (convex) moves down as the person raises the arm
Concave Moving on Convex:
When a concave bone moves, its surface moves in the same direction as the intended bone movement
Example: Knee movement (femur and tibia joint)
Tibia (concave) moves in the same direction as the person flexes or extends the knee
Saddle Joint (Thumb CMC Joint):
Has both concave and convex surfaces
Allows for complex movements combining both principles
Kinematic Chains
Open Chain Movement:
Distal segment moves while proximal segment is fixed
Used to enhance specific muscle strength and range of motion
Example: Raising legs
Closed Chain Movement:
Distal segment is fixed while proximal segments move
Requires coordination among multiple joints and co-contraction
Example: Standing up, sitting down
Important Concepts
Joint Congruency: How well joint surfaces match
Close-Packed Position:
Joint surfaces are tight and ligaments are stretched
Prone to injury but used post-injury for proper healing and preserving ligament length
Open-Packed Position:
Joint surfaces are loose and ligaments are relaxed
More comfortable but can lead to shortened ligaments if used excessively
Clinical Applications
Joint Mobilization Techniques:
Use knowledge of osteokinematics and arthrokinematics
Techniques: Compression, Traction, Shear force, Bending force, Torsion force
Applications aimed at realigning joints or enhancing range of motion through manual interventions
Summary
Successful rehabilitation and training depend on understanding and correctly applying the principles of convex-concave movements and kinematic chains. Clinicians use varied techniques to ensure proper joint mechanics and facilitate recovery.