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Four components of joint function-SI Joint (Diane Lee, physiotherapist)

The Integrated Model of Function (Lee & Vleeming) addresses 4 separate components which are essential for optimal function. The primary functional requirement of the pelvis is to transfer load between the trunk and the lower extremities. The first component is called "form closure". This term was coined by Andry Vleeming and Chris Snijders."

"Form closure addresses how a joint's shape and its ligaments contribute to stability. In other words, how does the integrity of the joint help to prevent shearing and excessive translation between the two joint surfaces when under load. At the SIJ, vertical forces must be controlled during walking, sitting and prolonged standing while forward and backward forces (anteroposterior translation) must be controlled during forward bending activities such as vacuuming, making beds or putting on your shoes."

"The second component of our model is called Force closure - another term coined by Vleeming and Snijders. This component addresses how and what extra forces are necessary to control translation between two joint surfaces when load is applied. The necessary force for controlling shear at the SIJ is compression. Compression is provided by the deep stabilizing muscles of the low back and pelvis which are transversus abdominis, multifidus and the pelvic floor. Collectively, these muscles have been referred to as the core muscles."

"The third component of our model is motor control. Motor control addresses the nervous system and is about the co-ordination or co-activation of these deep stabilizers. One of the world's leading research teams from the University of Queensland (Richardson, Jull, Hodges & Hides) have investigated the timing of these muscles in low back pain patients. They found that normally, these deep stabilizers should contract before load reaches the low back and pelvis so as to prepare the system for the impending force. They found that in dysfunction, there is a timing delay or absence of contraction of these muscles and consequently the system is not stabilized prior to loading. They also found that recovery is not spontaneous, in other words - the pain may go away but the dysfunction persists."

"The fourth component of our model addresses the role that our emotional state has on our ability to motor control effectively. It is well known that stress, anxiety, fear and pain all impact our emotional state and we now know that this state impacts our ability to motor control. Several studies are currently underway to specifically look at the impact of attention deficit, stress, fear etc on the core muscles. Holstege has shown that the emotional state is critical to health and recovery since it is through the muscle system that the mind ultimately expresses itself."

Vleeming A, Stoeckart R, Volkers A C W, Snijders C J 1990a Relation between form and function in the sacroiliac joint. 1: Clinical anatomical aspects. Spine 15(2): 130-132.

Vleeming A, Volkers A C W, Snijders C J, Stoeckart R 1990b Relation between form and function in the sacroiliac joint. 2: Biomechanical aspects. Spine 15(2): 133-136.

Hides J A, Stokes M J, Saide M, Jull G A, Cooper D H 1994 Evidence of lumbar multifidus muscles wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine 19(2): 165-177.

Hides J A, Richardson C A, Jull G A 1996 Multifidus recovery is not automatic following resolution of acute first episode low back pain. Spine 21(23): 2763-2769.

Hodges P W, Richardson C A 1996 Inefficient muscular stabilization of the lumbar spine associated with low back pain. A motor control evaluation of transversus abdominis. Spine 21(22): 2640-2650.

Holstege G, Bandler R, Saper C B 1996 The emotional motor system. Elsevier Science.