I think Alexia's comment is an example of the confusion between concept and terminology. While I appreciate what she is trying to say; first, it's not correct to say "ultimate stress" - Ultimate stress is an engineering term to mean the max stress a material can withstand before failure - it is the peak of the stress/strain curve of a material before failure. So its not really a condition that would occur in any physiological joint position. Second, in the so called closed-packed position, only some parts of the capsule are under stress as I stated above with the shoulder example. Third ,the statement about smoothness has nothing to do with congruency. Congruency is when the radias of curvature of the two articulating surfaces are most coincident. The movement possible in a closed pack position is limited only in certain directions - not all directions ( determined by the asymmetrical loading of capsuloligamentous tissue.).

So my suggestion is to encourage disuse of the term closed-pack , because it is misleading and mis-represented clinical Jargon with little scientific evidence to support the clinical assumptions ascribed to it. If you want to describe a specific joint position then just describe the position - In addition don't just assume that the joint is in some max congruent position or some max capsular stress position unless we have some evidence to back that up. We need to move toward more evidence based clinical practice and a first step toward this is to challenge/reevaluate many of the traditional assumptions of the past.

Joint congruency is maximal at the closed-packed position, as maximum contact exists between the two surfaces. Congruency is the concept of "fitting well together".

I agree with the Alicia Fernandez-Fernandez answer

Hi Alicia Fernandez-Fernandez.

Thanks for your answer but in publications that I readed there is coflict exist with your definition.

As it comes in biomechanical basis of human movement 3rd edition :

"the joint is in a close-packed position in full extension when the lower body is stabilized on the pelvis." ( page 196)

but at the another page:

"At 90° of flexion with a small amount of rotation and abduction, there is maximum congruence between the femoral head and the socket." (page 197).

So if the maximum congruency is close-packed position why this two position for the Acetabulofemoral joint is not the same?

actually there is more confliction exist in the publication as well.

so if you understand it please noted. thanks.

There are always exceptions to any rule. In this case, the hip is one of them. From Levangie and Norkin "Joint structure and function" book, 5th ed., p. 366: "in contrast with most other joints in the body, the close-packed position for the hip is not the position of maximal articular contact (congruency)".

Can we say that in congruency other structures like fibrocartilaginuos disc, meniscus and ... are important components for determination but in closed-pack position just the contact between the bones are Criterion for designation of the position.

thanks for your reply.

Dear Mohsen,

I think you are on the right track questioning the clinical concept of "close-packed " joint positions. The text book definitions do state it in terms of max congruency but also state it as a position of max capsular tightening allowing for no translatoty motion in the joint . Both of which fail. 1. Capsular ligamentous structures are asymmetrically tightened at points in the range and actually drive much of the translatory motion ( with incidentally is contradictory to another clinical "rule" - convex-concave ) 2. The positions are generally not the position of max articular congruency . Take for example the Glenohumeral joint - The Close pack position is stated as Abd + ER . However in this position, the anterior capsule is tightened much more than the post Capsule and actually causes , or drives some posterior translation of the humeral head on the glenoid - so the real kinematics do not support the definition of the close pack position. Much of the clinical jargon about arthrokinematics has been perpetuated and ingrained before experimental techniques were available to challenge them. These are important issues because they are used as rationale for treatment techniques such as mobiliszation.

Dear Mr. Kevin Mcquade.

According to your elucidation, is there any right definition exist for this two terms in text which do not have any conflict with the real kinematics or other clinical and biomechanical rules as well or should making new definitions for this two terms or should just disregard them.

thaks for your reply.

Closed packed position is theultimate stress position of the joint-capsula. Congruency the dimension of fitting together of 2 bone parts and the smoothness of movement of the joint. Yes, a joint will have a minimal movement in a closed packed position although a perfect congruency exists.

I think Alexia's comment is an example of the confusion between concept and terminology. While I appreciate what she is trying to say; first, it's not correct to say "ultimate stress" - Ultimate stress is an engineering term to mean the max stress a material can withstand before failure - it is the peak of the stress/strain curve of a material before failure. So its not really a condition that would occur in any physiological joint position. Second, in the so called closed-packed position, only some parts of the capsule are under stress as I stated above with the shoulder example. Third ,the statement about smoothness has nothing to do with congruency. Congruency is when the radias of curvature of the two articulating surfaces are most coincident. The movement possible in a closed pack position is limited only in certain directions - not all directions ( determined by the asymmetrical loading of capsuloligamentous tissue.).

So my suggestion is to encourage disuse of the term closed-pack , because it is misleading and mis-represented clinical Jargon with little scientific evidence to support the clinical assumptions ascribed to it. If you want to describe a specific joint position then just describe the position - In addition don't just assume that the joint is in some max congruent position or some max capsular stress position unless we have some evidence to back that up. We need to move toward more evidence based clinical practice and a first step toward this is to challenge/reevaluate many of the traditional assumptions of the past.

PS: Attached are some good references on Arthrokinematics

Thank you Kevin for your very technical and clear statement and therefor attribution to the clearance of the probable misconception of MCPP.

Usually the two go hand in hand. Close pack by definition is the position of maximum stability in the joint, and the joint surfaces being congruent will also contribute to stability. There are always exceptions but unless specific definitions are required, the two terms are closely interlinked, in my humble opinion.

Arturo, I respectfully disagree - the "close-pack" position of the shoulder is described as abduction and external rotation . However this is NOT the position of maximum stability of the joint and it is NOT a position of maximum Concruency.

thanks for your comments kevin. you have picked a joint that by its morphology is always a tricky one to catergorise! i apologise as i have been perhaps a little loose with terminology, and i did say there are exceptions.

however, as you state, the shoulder close pack is abd and ext rot, and according to grays anatomy, 37th ed p 501, it does describe maximum congruency as equivalent to close pack. kapandji describes "...the shoulder maximally stable as when the superior humeral head is in contact with the glenoid, as the middle and inferior GH ligs are taut. this position of abduction at 90 degs corresponds to the locked or close pack position as described by mcconaill".

in my mind, as ligs are taut in this position, it would follow that maximum stability is achieved under normal physiological range. clearly, its the position that commonly is associated with disclocation, but this is pathology, not normal physiological range.

it would be great to hear your thoughts on where you think maximum stability and maximum congruency occur. i look forward to your reply. regards.

Hi Arturo,

Ok, Grays 37th description of the arthrokinematics is based on the observations of McConnaill . McConnaill was primarily a geometrist and based some of these early theories purely on the geometry of the joint with out regard to any capsuloligamentous drivers. None of those descriptions were based on any on any direct experimentation or measurement. Kapandji was a wonderful artist but the material is empirical and not based of any validation data – and has several exceptions. This is not to detract from the historical significant of early observation, but the point is that now we have imaging and motion analysis techniques to measure joint kinematics that we did not have in the 1940’s and 1950’s.

As I replied above ,max congruency is when the radius of curvature of two articulating surfaces are most closely matched. This is not the case with the arm in the so-called Close-pack position. While the Mid and inf GH lig are may have increased tension with increasing abd and ER – they certainly do not “lock” the joint. With increasing Abd and ER Anterior capsule tension tends to push the humeral head posterior on the glenoid away from a position of maximum congruency (in the normal shoulder). If here is anterior capsular laxity then this does not occur and the glenoid is allowed to migrate anteriorly – into a position of “clinical instability”.

Max congruency of most joint occurs in a Neutral position of the joints – and for the GH joint this is mid elevation in a plane 30-40 degrees anterior to the coronal plane – (commonly called scapular plane).

Max Stability is a state of mechanical equilibrium and occurs when the net forces acting on a rigid body equal 0. So whenever you have unequal forces or Moments acting you are not in a state of maximal stability.

Thanks for that comprehensive answer Kevin. It makes a lot of sense. Will consider that principle in others areas !

I think that between Kevin and Arturo is the answer

Joint stability is close-pack, but congruency is a geometrical relationship of articular surfaces and its rotational axis.