Joint Surface Positions or Joint Congruency

Parts of the capsule and supporting ligaments are lax. There is minimal congruency between the articular surfaces. Further passive separation of the joint surfaces can occur in this position.

Because the ligaments and capsular structures tend to be more relaxed, joint mobilization techniques are best applied in the open-packed position.

For example, if you place your knee in the fully extended position, you can manually move the patella slightly from side to side and up and down.

However, if you flex your knee, such patellar movement is not possible. Therefore, the close-packed position of the patellofemoral joint is knee flexion.

open-packed or loose-packed position

It is also referred to as the resting position.

closed-pack, position

It usually occurs at one extreme of the ROM.

When a joint is congruent, the joint surfaces have maximum contact with each other, are tightly compressed, and are difficult to distract (separate). The ligaments and capsule holding the joint together are taut.

This is known as the close-packed, or closed-pack, position.

By the nature of the characteristics of a close-packed position,

a joint is often in this position when injured.

The surfaces of a joint

are congruent in one position and incongruent in all other positions.

The convex surface glides

in the opposite direction from the distal end of the moving bone.

Also, when a joint is swollen,

it cannot be moved into the close-packed position.

How well joint surfaces match or fit is called

joint congruency.

When ligaments and capsular structures are tested for stability and integrity, the joint is usually placed in

the close-packed position.

In all other positions,

the joint surfaces are incongruent.

The position of maximum incongruence is called

the open-packed or loose-packed position.

It is these open-packed positions that allow for

the roll, spin, and glide that are necessary for normal joint motion.

For example, a knee joint that sustains a lateral force when it is extended (closed-packed position) is much more likely to be injured than

when it is in a flexed or semiflexed position (loose-packed position).