Accessory Movements

As we all know that in our body , Most of the movements occurs at joint which we are able to see like Flexion/Extension, Abduction/Adduction, Rotations....

But there are some movements also occur at each joint  which we are unable to see, Want to know about it? Let's see....

Accessory Movements :- The movements which occur between the joint surfaces also known as Arthrokinematic .These movements include roll, spin and slide.

• These movements are not voluntary controllable by an individual.
• To occur these movements, one joint surface is relatively stable and serves as a base for the motion , whereas the other surface moves on this relatively fixed base.

1) Roll :- A roll refers to the rolling of one joint surface on another joint surface as a tire rolling on the road.

• Direction of rolling is describe by the direction of movements of the bone.
• Multiple points along one articular surface contact multiple points on another articular surface. 

eg :-In standing, while knee flexion femoral condyle posteriorly roll on relatively fixed tibial condyle.

 2) Slide :-It's a pure translatory motion, refers to the sliding of one component over another as when a braked wheel skids.

•   Direction of slide/glide depend upon the shape of the articular surface(convex/concave)                     
•   A single point on one articular surface contacts multiple points on another articular surface.

eg :-In standing, while knee flexion femoral condyle slide/glide anteriorly on relatively fixed tibia.

 3)  Spin :- It's a pure rotatory motion, refers to rotation of the one articular surface against the articular surface of another bone as a toy top rotating on one spot on the floor.

•   A single point on one articular surface rotates on a single point on another articular surface.

eg :-At the elbow , the head of the radius spins on the capitulum of the humerus during supination and pronation of the forearm.     

Now the question arise that:-
1) Is these movements depend on any factor or not?

• Yes, the type of accessory motion that occur at a particular joint depend on the shape of the articulating surfaces.

             


   Convex - Concave rule

1) When Concave surface is moving on relatively fixed convex surface, Rolling and Sliding occur in same direction of movement of bone.eg :-In high sitting, while knee flexion tibia (concave) roll and glide posteriorly on relatively fixed femur(convex).

2) When Convex surface is moving on relatively fixed concave surface, Sliding occur in opposite direction and Rolling occur in same direction of movement of bone. eg:-In standing, while knee flexion femur(convex) roll posteriorly and slide antetiorly on realtively fixed (concave) tibia.

 Conclusion:-

     In this topic we almost cover the movements which are occuring between the articulating joint surfaces. In which direction this movements is occurring(same/opposite) with respect to the bone movement. Factor on which they movements depends like joint surface such as convex/concave.


Now again here a question arise, Why these movements are important?

If you know the answer or wanted to know the answer, you can comment below
OR
If you have any query regarding this topic please comment below

Youtube: 

Reference Article: 

To know more in depth you can also go through this link reference.
https://lukedelorenzo.wordpress.com/2011/07/27/arthrokinematics-an-important-biomechanical-concept/amp/

RESOURCES :-

  1) Joint structure and function, a comprehensive analysis 5th edition by Pamela K. Levangie, Cynthia C. Norkin

2) Kinesiology Of Musculoskeletal System, foundations for rehabilitation 3rd edition by Donald A. Neuman

3) Therapeutic Exercise, Foundations and techniques 6th edition by Carolyn Kisner, Lynn Allen Colby

BY MANISHA GOLA (PHYSIOTHERAPIST)