by Erik Dalton Ph.D.
All joints move in a very specific fashion and have a very precise range of movement. A joint’s normal range of motion is defined by the connective tissue that binds it, particularly the ligaments. Oddly, the muscles, tendons and fascia that cross the joint dictate approximately 80% of the stability of a joint with less than 20% accomplished by ligaments.
The term “joint play” refers to the small amount of movement in a synovial joint that is independent of voluntary muscle movement, whereas, “joint centration” describes the optimal alignment of joints.
When therapists and movement specialists establish optimal joint play and joint centration, we reduce wear and tear on the joint by allowing forces to be transferred in the most efficient way possible. Think of joint centration like the wheel on a car. If the center of rotation is aligned with the center of the hub, it will deliver the most efficient performance. But when this neutral position becomes misaligned, the wheel spins incorrectly and may lead to future mechanical problems. We commonly see this in Upper Crossed postures where slumped shoulders lead to “decentration” of the glenohumeral joint and subsequent rotator cuff impingement syndromes (Fig. 1).
Commonly, joint play dysfunction is the cause of secondary muscle changes we see in clinic. The secondary muscle changes are mainly atrophy and spasm. Spasm is usually caused by nature’s attempt, reflexively, to prevent painful joint movements. Of course, this whole process is interlinked with the actions of the nervous system. Whatever the reason for the loss of joint play, when a joint is not free to move, the muscles which move it cannot be free to move and compensations occur (Fig. 2).
All muscles can act as stabilizers or mobilizers depending on joint position and coordinated motor control. Balance of mobilizers and stabilizers acting at a joint results in optimal joint centration. Loss of centration occurs when phasic (mobilizers) muscles are forced to stabilize. Non-optimal joint centration can lead to whole body stress and, conversely, stressful activities can cause loss of proper joint centration. This is why we must help down-regulate our client’s sympathetic nervous system with good bodywork, and keep them moving correctly through specifically designed joint centration home retraining exercises.
When we align and properly tone the musculofascial system, the transmission of nerve impulses is more efficient, which may prevent future joint play and ‘decentration’ dysfunction. One would not want to administer muscle strengthening exercises without first creating joint play. Otherwise, articular surfaces within a joint will not glide smoothly on one another. This may lead to degradation of the surfaces and ultimately capsulitis or osteoarthritis.
Loss of joint play and /or joint centration is often initially expressed by periodic twinges of pain or discomfort. It may also lead to more joint fatigue and greater pain after use. Eventually it may amount to ongoing nagging discomfort or pain during use. So what should we do first, stabilize or mobilize? Both have significant positive clinical benefits, so it is most advantageous to do both during the same treatment session.
In the video above, I demonstrate a few simple techniques for assessing and correcting for loss of joint play. In my upcoming 3-DVD set entitled, “Motion is Lotion”, Paul Kelly and I add tailor-made joint centration training to help restore lost synovial fluid lubrication to joints and hyaluronic acid to adhesive or injured fascia.