It’s funny. There are days when I think I know a lot and days when I think I know very little. I always say, there are no stupid questions, just those of us who insist on remaining stupid in our silence. One great example of this in my life are the terms closed pack position and open pack position. I have heard these terms used in lectures for years and just never bothered to say “what the heck are you talking about”. I can’t imagine how many of you have the same experience I do, sitting in your ignorance. I’m lucky enough to have a monthly meeting with my friend Dr Daniel Dyrek. If you have heard me speak you have heard me say 100’s of times that Dan is the smartest guy I know. His knowledge of the human body leaves me in awe. So, I took it upon myself to ask Dan “what is the closed pack position?”
Dan explained that in the closed pack position the joint is positioned so that all of the connective tissues are tight.
The book Chiropractic Care of Special Populations defined close pack as “ the joint position where the capsule and ligaments are taut. In this position the articular surfaces of the joint are as close together as possible”
The opposite of close pack is loose pack. Loose pack is defined by the same source as the “joint position where the capsular and ligamentous fibers are maximally lax. Open pack is the position to evaluate joint play”.
For the shoulder the closed pack position is best described as a 90/45 position. The humerus is parallel to the floor and is at 45 degrees in the frontal plane. In this position ,often referred to as the plane of the scapula, we have maximum articulation of the humeral head in the glenoid. As a result, this tends to be the ideal position to strengthen the external rotators. Many times we see the external rotators strengthened in a position with the arm at the side or with a towel roll under the arm to create a small degree of abduction. This position may allow the athlete or client to learn to distinguish external rotation from scapular motion but once the athlete or client can differentiate it is important to move to the closed pack position and eventually to the 90/90 position. The key to the 90/90 position is that the athlete or client learns to separate elevation from internal rotation and depression from external rotation. In many athletes what passes for internal and external rotation is actually primarily scapula motion.
For shoulder rehab we need to think about not what is safe but about what the optimal position is to train in. No one needs rotator cuff strength or motor control when their arm is at their side. The fact that they may get better recruitment of a particular muscle is not relevant. The need for the rotator cuff to do it’s job is paramount in the throwing motion.
T o complicate matters more, as I learn Postural Restoration Institute concepts I am suddenly exposed to something called Optimal Articular Congruence. Optimal Articular Congruence is defined as the optimal position of the joint i.e the ball and socket fit best in the position of Optimal Articular Congruence.
As I think about close pack and open pack and Optimal Articular Congruence, I keep coming back to the “the more you know, the more you realize you don’t know”.