The Concave-Convex Rule is given by Freddy M. Kaltenborn. It describe which movement is happening within joint with concave and convex surfaces. Most literature mention that the rule can be used to determine in which direction limited joint should be mobilized but this idea has some flaws described by different authors. The rule should rather be used to guide us as to which part of the joint capsule we want to examine during our assessment or stress during our treatment.
The rule is consequences of the fact that the axis of movement for the convex joint partner is within the bone itself, whereas for a concave partner the axis of movement is outside the bone. For this reason the rolling and gliding always occur together. So if we are moving the convex surface, the glide component is always occur in the opposite direction of the roll. If we are rolling the convex bone part, it would eventually roll off it’s fixed concave bone part without a glide component through a glide in the opposite direction which occur as the axis of rotation is within the convex bone part. The joint surface stay in touch with each other and the greater range of motion is possible.
On the another hand, if we are moving the concave joint partner the glide comment always occur in the same direction around the axis of rotation that lies in the convex bone partner. So if we’ll only to roll, the movement would be limited very early by gliding in the same direction and a greater motion is possible.
Osteokinematics:-
Osteo means bone and kinematics means movement or motion. Osteokinematics is defined as the movement of bone through a range of motion around the axis of a joint. These are the clear movement of body bone and are visible from the outside. These are the large movement which happens between two bones. Example – Flexion/Extension, Abduction/Adduction, Lateral and Medical rotation etc.
Arthrokinematics:-
Arthro means joint and kinematics means motion or movement. Arthrokinematics is defined as the movement of joint surface. These movements are not visible from the outside. These are small movement present at the joints. These movements involve rolling, sliding and spining.
Concave-Convex Rule:-
The Concave-Convex rule helps us to know which part of the bone is moving and in which direction it’s moving. The convex surface is rounded outward and the concave surface is rounded inward.
This rule tell us when a convex surface of bone is moving over a concave surface of another bone, then rolling and gliding will occur in the opposite direction. Means the direction of Osteokinematics and Arthrokinematics will be in a opposite direction. On the another side, when a concave surface of bone is moving over a convex surface of another bone, then rolling and gliding will occur in the same direction. Means the direction of Osteokinematics and Arthrokinematics will be in a same direction.
Example – let’s take an example of glenohumeral joint of shoulder. The head of humerus is convex surface and glenoid cavity of scapula is concave surface. When we do shoulder flexion, the rolling occur in the superior side and gliding occur in the posterior side. Means the rolling and gliding are in opposite direction because convex surface is moving over concave surface.
This Concave-Convex rule easily tell us the direction of joint surface movement.