Summary of Convex Concave Rule in Arthrokinematics
Convex Concave Rule in Arthrokinematics: Student's Guide
Introduction
Arthrokinematics of joints examines the movement of joint surfaces (articular surfaces) and how they slide and rotate relative to one another during movement. This is useful for understanding joint function in rehabilitation, in guiding therapeutic techniques, and in assessing range of motion.
Definition: Arthrokinematics examines the subtle movements between the articular surfaces of joints, specifically gliding, rolling, and spin.
Basic Concepts
Convex and Concave Surfaces
- Convex surface — bulges outward (a spherical or rounded protrusion). Imagine the surface as the outside of a ball.
- Concave surface — is indented, "hollowed out." Imagine a bowl that something fits into.
Definition: A convex surface is an articular surface whose curvature faces outward; a concave surface is an articular surface whose curvature faces inward.
The Convex–Concave Rule
- The rule depends on which surface actively moves during motion (i.e., the bone bearing the surface moves) and which one is stationary.
- If the moving surface is concave, the articular surface and the bone slide in the same direction.
- If the moving surface is convex, the articular surface slides in the opposite direction to the bone.
Definition: "Moving surface" refers to the one that slides relative to the other surface during active or passive movement.
Illustrative Examples
Example 1 — Elbow (Concave Surface Moves)
- Head: humerus (convex)
- Articulating Bone: ulna (for simplicity, imagine the articular surface of the ulna as concave)
- When the ulna moves as a concave surface, the articular surface of the ulna slides in the same direction as the bone's movement (i.e., the articular surface and the bone move 'synchronously').
Example 2 — Shoulder (Convex Surface Moves)
- Head: humerus (convex)
- Socket: glenoid fossa on the scapula (concave)
- During abduction or adduction, when the humerus moves as a convex surface, the articular surface of the humerus slides in the opposite direction to the movement of the humerus as a whole.
Comparison Table
| Situation | Moving Surface | Direction of Joint Glide Relative to Bone Movement |
|---|---|---|
| Elbow (e.g.) | Concave | Same direction |
| Shoulder (e.g.) | Convex | Opposite direction |
Practical Application in Physiotherapy
- During joint mobilization, we select the glide technique based on which surface we want to move relatively.
- In cases of pain or restricted range of motion, the therapist applies the glide direction to align with the rule and restore physiological movement.
- Understanding the rule helps in educating patients on why a specific exercise or direction of pressure "helps" improve movement.
Steps for Applying the Rule in Therapeutic Mobilization
- Identify which bone and surface is moving (convex or concave).
- Determine the direction of therapy according to the rule (same or opposite direction of glide).
- Apply a gentle glide in the determined direction during passive mobilization.
- Monitor pain and range of motion; adjust force and direction according to the patient's reaction.
Useful Tips
- Always validate through observation and patient response; anatomical variations can affect the perception of movement.
- Combine glide with active exercise for improved motor learning.
💡 Did you know?Fun Fact: Did you know that the convex-concave rule not only helps with peripheral joints but is also useful for understanding movement in the temporomandibular joint?
Summary
- Distinguish between convex and concave surfaces (convex: curves outward, concave: curves inward).
- If a concave surface is moving, the joint glide occurs in the same direction as the bone.
- If a convex surface is moving, the joint glide occurs in the opposite direction to the bone.
- This rule helps guide the selection of mobilization direction and improve joint function.
Arthrokinematics of Joints
Klíčové pojmy: Arthrokinematics describes the glide, roll, and spin between articular surfaces., A convex surface bulges outwards, while a concave surface is inwardly curved., When a concave surface moves, the glide occurs in the same direction as the bone's movement., When a convex surface moves, the glide occurs in the opposite direction to the bone's movement., Elbow: ulna (concave) – glide in the same direction as movement., Shoulder: humerus (convex) – glide opposite to the direction of movement., During mobilization, identify the moving surface and apply the glide according to the rule., Combine passive glides with active exercises for better results., Monitor the patient's pain and range of motion when applying techniques., The rule helps explain the choice of direction for therapeutic force.
## Introduction
Arthrokinematics of joints examines the movement of joint surfaces (articular surfaces) and how they slide and rotate relative to one another during movement. This is useful for understanding joint function in rehabilitation, in guiding therapeutic techniques, and in assessing range of motion.
> **Definition:** Arthrokinematics examines the subtle movements between the articular surfaces of joints, specifically gliding, rolling, and spin.
## Basic Concepts
### Convex and Concave Surfaces
- **Convex surface** — bulges outward (a spherical or rounded protrusion). Imagine the surface as the outside of a ball.
- **Concave surface** — is indented, "hollowed out." Imagine a bowl that something fits into.
> **Definition:** A convex surface is an articular surface whose curvature faces outward; a concave surface is an articular surface whose curvature faces inward.
### The Convex–Concave Rule
- The rule depends on which surface *actively* moves during motion (i.e., the bone bearing the surface moves) and which one is *stationary*.
- If the **moving surface** is **concave**, the articular surface and the bone slide in the **same** direction.
- If the **moving surface** is **convex**, the articular surface slides in the **opposite** direction to the bone.
> **Definition:** "Moving surface" refers to the one that slides relative to the other surface during active or passive movement.
## Illustrative Examples
### Example 1 — Elbow (Concave Surface Moves)
- Head: humerus (convex)
- Articulating Bone: ulna (for simplicity, imagine the articular surface of the ulna as concave)
- When the ulna moves as a concave surface, the articular surface of the ulna **slides in the same direction** as the bone's movement (i.e., the articular surface and the bone move 'synchronously').
### Example 2 — Shoulder (Convex Surface Moves)
- Head: humerus (convex)
- Socket: glenoid fossa on the scapula (concave)
- During abduction or adduction, when the humerus moves as a convex surface, the articular surface of the humerus **slides in the opposite direction** to the movement of the humerus as a whole.
## Comparison Table
| Situation | Moving Surface | Direction of Joint Glide Relative to Bone Movement |
|---|---:|---|
| Elbow (e.g.) | Concave | Same direction |
| Shoulder (e.g.) | Convex | Opposite direction |
## Practical Application in Physiotherapy
- During joint mobilization, we select the glide technique based on which surface we want to move relatively.
- In cases of pain or restricted range of motion, the therapist applies the glide direction to align with the rule and restore physiological movement.
- Understanding the rule helps in educating patients on why a specific exercise or direction of pressure "helps" improve movement.
## Steps for Applying the Rule in Therapeutic Mobilization
1. Identify which bone and surface is moving (convex or concave).
2. Determine the direction of therapy according to the rule (same or opposite direction of glide).
3. Apply a gentle glide in the determined direction during passive mobilization.
4. Monitor pain and range of motion; adjust force and direction according to the patient's reaction.
## Useful Tips
- Always validate through observation and patient response; anatomical variations can affect the perception of movement.
- Combine glide with active exercise for improved motor learning.
Fun Fact: Did you know that the convex-concave rule not only helps with peripheral joints but is also useful for understanding movement in the temporomandibular joint?
## Summary
- Distinguish between convex and concave surfaces (convex: curves outward, concave: curves inward).
- If a concave surface is moving, the joint glide occurs in the same direction as the bone.
- If a convex surface is moving, the joint glide occurs in the opposite direction to the bone.
- This rule helps guide the selection of mobilization direction and improve joint function.